Echidnas blow snot bubbles to keep their noses cool

January 23, 2023 • 11:15 am

You’ve heard about about platypuses, the monotreme egg-laying mammal that lays eggs, a primitive condition inherited from the ancestor of all modern mammals (and their earlier reptilian ancestors). But perhaps you also know of the “echidnas“, or “spiny anteaters” (not very related to regular anteaters), also in the order Monotremata and the only other egg-laying mammal. (These are not marsupials; they diverged from the placental/marsupial mammal group, called therians, between 250 and 160 million years ago.)

The living monotremes comprise four species of echidna and only one species of platypus (Ornithorhynchus anatinus), and these two groups diverged from each other between 57 and 21 million years ago. Further, the monotremes diverged from the “regular” (therian) mammals between 218 and 187 million years ago.

The article at hand is about one of the four echidna species, the short beaked-echidna (Tachyglossus aculeatus). Here’s what it looks like:

Click on the article below to read about how echidnas keep cool in the hot climate of Australia (the pdf is here, the full reference is at at bottom, and there’s a popular article here.  But the article below, from Biology Letters published by Britain’s Royal Society, is short and easy to read:

So the issue is this: earlier studies had demonstrated that this species had a low thermal tolerance, with a lethal core body temperature of 38ºC (100.4º F) and a lethal air temperature of just 35ºC (95º F). (From now on I’ll just give the Celsius temperatures, as you should get familiar with the conversion.) Yet the echidna is found in Australian habitats where the air temperature is higher than this, so they must have a way to cool off. The paper reports thermal-imaging studies of wild echidnas to see how they do this.

Clearly, the echidna must have some way to lower the temperature it encounters in the wild, which the authors call a “thermal window” or “regions of the animal’s body surface that vary heat exchange with the environment being ‘opened’ or ‘closed’ by changes in exposure and/or blood flow.” (Below are some cool examples of how other species do this.)

The authors measured the echidnas’ body temperature by thermal imaging, and estimated the ambient temperature as the average of the air temperature and tje ground temperature. They also measured a “wet bulb” temperature, which is the temperature measured by a wetted thermometer bulb. Wet-bulb temperature is cooler than the air temperature because the evaporation of the water from the bulb cools it off.

They found two ways that echidnas cool themselves off at higher temperatures. The temperature comparisons of echidna body parts with environmental temperature was measured by plotting, over a variety of echidnas observed at different temperatures, the wet bulb temperature (x axis) versus the surface temperature of the animal (y axis).  That’s shown below, but first one observation.

The first way of cooing the authors found was seeing the animals press their relatively furless (and spineless) inner leg an belly surfaces against the cool soil.  This is similar to what kangaroos do; see below. The spines also help keep the sun off their bodies, and there is a subcutaneous fat layer, into which the spines are embedded, that also provides insulation.

The second way of cooling is the swell finding given in the headline. You can see it below in the lower right section of the following graph. It shows body temperatures versus wet bulb temperature for various parts of the echidnas’ bodies (remember, this is done by thermal imaging). The body areas measured are shown in green, and the body temperatures measured at varying wet-bulb temperatures for each body area, are shown as dots, one for each echidna part measured. Measurements were done on 124 echidnas (some may have been duplicates, as they couldn’t identify individuals) at the Dryanra Woodland and Boyagin Nature Reserve in the West Australian wheatbelt, 170 k southwest of Perth, in western Australia:


(From paper): Figure 1. Surface temperature of various body regions plotted against wet bulb globe temperature (WBGT) for 124 active short-beaked echidnas (Tachyglossus aculeatus) filmed with an infrared camera in the West Australian wheatbelt. The solid line represents a slope = 1 for WBGT, the dashed line the observed slope for the relationship; asterisks indicate that the slope is significantly different from 1. The inset thermal image shows the body region represented by each panel, outlined with a green polygon.

What you see is that the surface temperature (the height of the dots) is, for six regions of the body, higher than the wet-bulb temperature, which means there’s no evaporative cooling of those warm body surfaces. But look at the “beak tip” at lower right. At all the wetbulb temperatures, the beak tip temperature is the same as the wet-bulb temperature. That means that somehow there is extra cooling going on at the tip of the snout.

How do they do this? They blow snot bubbles out their nose, which, when they burst, keep the nose moist, thus cooling the echidna. In effect, the the beak is a “snot bulb.” Or, to quote the authors:

We identify the beak tip of short-beaked echidnas as a unique type of evaporative window. The beak tip, containing a large dorsal blood sinus, is kept moist to facilitate electroreception. An additional role of this moist surface is evaporative cooling of the underlying blood within the sinus; with a slope equivalent to 1 and minimal intercept, the beak tip functions as a wet bulb globe thermometer. At high Ta [air temperature] echidnas blow mucus bubbles, adding moisture to the beak tip . This unique nasal evaporative window is of particular value for echidnas (which do not pant, lick or sweat) especially under conditions where environmental temperature exceeds Tb [core body temperature] and evaporation is the only avenue available for heat loss.

Here’s a video from Science News about the cooling.  Note that here the lightest areas are the hottest and the darkest are the coolest. Check out the snout tip, circled at 5 seconds in. It’s very dark!

Upshot: Echnidnas have evolved to cool themselves off by blowing snot bubbles when it’s hot. The bubbles’ bursting keeps the animal cool, especially because the snout is well equipped with lots of blood vessels that radiate the heat.

Here’s the authors’ description about how other species use evaporative cooling, including the fact that kangaroos lick their forearms to cool off when it’s hot:

. . . there have been few descriptions for endotherms of specialized evaporative windows where endogenous water is behaviourally applied to areas with specialized vasculature. The classic examples of evaporative windows are for storks and turkey vultures, which urinate on their legs that contain extensive subcutaneous vascularization, facilitating EHL. Seals on rocks similarly urinate to wet their ventral surface and vascularized flippers to enhance EHL, while the licking of vascularized forearms by macropods is the best-known mammalian example.

Storks and seals piss on themselves to cool off! I bet you didn’t know that.

Here’s an Attenborough video of red kangaroos (Osphranter rufus) cooling themselves by licking their highly vascularized forearms (you can skip to 2:05 to see it, as well as thermal images showing the cooling). They also stay in the shade and dig down into the cooler soil beneath the surface and lie down on the cool soil.


Now we can add to these examples of evaporative cooling the snot bubbles of echidnas.

h/t Greg Mayer


Cooper C. E. and Withers PC. 2023. Postural, pilo-erective and evaporative thermal windows of the short-beaked echidna (Tachyglossus aculeatus).Biol. Lett.19: 20220495

Flannery, T.F., T.H. Rich, P. Vickers-Rich, T. Ziegler, E.G. Veatch, and K.M. Helge. 2022. A review of monotreme (Monotremata) evolution. Alcheringa 46(1): 3-20.


Trilobite “horns” may have been used as weapons in male-male combat

January 19, 2023 • 9:15 am

Years ago I met Richard Fortey at the inaugural meeting of Spain’s new evolution society, and found him an affable and lovely guy. He’s a paleontologist and writer, and I had the pleasure of reading and giving a positive review to his first book, Life:  A Natural History of the first Four Billion Years on Earthwhich is well worth reading (he’s written several other books, including Trilobite: Eyewitness to Evolution (also a good read).

And it’s four trilobite species that are the subject of Fortey’s new paper coauthored with Alan D. Gishlick, a geophysical sciences professor at Bloomsburg University, in PNAS, a paper you can read for free by clicking the title below (it’s free with the legal Unpaywall app., the pdf is here, the reference is at bottom, and judicious inquiry might yield a pdf if you can’t see the paper). Trilobites are common fossils, and were marine arthropods that went extinct without leaving descendants.

The upshot is that Gishlick and Fortey analyzed fossils of one species of trilobite found in Morocco, deriving from the Devonian (400 million years ago). This species, Walliserops trifurcatus, had a long trident attached to the front of their bodies, and tried to figure out what it was for. They also found one adult individual whose trident was a bit deformed (see below). Their conclusion is that these were weapons used by males to fight with other males, almost surely to compete for females. They are, posit the authors, the arthropod equivalent of reindeer horns. The other possible functions (feeding, digging, etc.) were largely ruled out.

Read on:

Here are four species of Walliserops, shown below. All specimens bear a rigid cephalic trident. W. trifurcatus has a slightly recurved trident that bends upwards, while the other species have tridents more flush with the surface of the sediment (all captions come from the paper):

Four recognized species of Walliserops: A. trifurcatus, UA 13447 (topotype); B. hammi, UA 13446 (holotype); C. tridens UA 13451 (holotype); D. lindoei ROMIP 56997. Images taken from photogrammetric models. (Scale bar, 10 mm.)

The obvious question is: what is this damn thing for?  And there are several hypotheses, all assuming that the structure was molded by natural selection (which includes sexual selection). The authors find evidence against all but one possible function. Here are the alternatives (of course, it could have been used for several things, but it’s likely that selection was wholly or largely on one function). Indented bits are quotes from the paper. The rest of the discussion concerns W. trifurcatus:

A.) Defense. Perhaps the structure could have been used to ward off predators, like the spines found on other trilobites.  Here’s how the authors rule this out:

However, such a function would have been difficult given the overall anatomy of the trident and the trilobite. The trident is rigidly attached and cannot be moved independently from the cephalon; it could only be flexed in a dorsal-ventral plane by the trilobite raising and lowering its cephalon. This would create further difficulties since the long genal spines limit how high the head could be angled without lifting the entire body. The trident, therefore, could not be employed in a versatile way, nor be presented as to defend from a predator attacking from above or behind. This morphology is not consistent with a defensive structure.

B.) A feeding structure.  Doesn’t seem likely:

A second possible function for the trident would be as an aid to feeding. Like all members of the Phacopida, Walliserops was probably a scavenger/predator, and it might be considered as a possibility that the trident was a comparatively sophisticated sensory device concerned with early detection of prey species—such as buried annelid worms—which could then be grasped by the endopods of the ventral limbs.

C.) Sensory detection of the environment.  This is also deemed unlikely from inspection of the structure:

However, examination of the trident in optical and scanning electron microscopy failed to find the arrays of cuticular pits or tubercles usually indicative of the presence of sensilla in fossil arthropods. Most groups of trilobites include species with exterior exoskeletal pitting that is preserved even if the intracuticular canals have been removed by calcite reorganization—and there is no evidence of such exterior pitting on the trident of Walliserops. The absence of evidence for specialized organs on the tines makes it unlikely that it was primarily a sensory apparatus.

D.) A spear to pierce prey:  Unlikely because the structure was inflexible, so the animal would have no way of accessing speared prey.

E.) An apparatus to dig, perhaps for prey.  The way it’s shaped and angled seems to preclude this (remember, it’s slightly recurved upward; see below):

Another possibility is that the trident may have been used to agitate sediment to disturb prey items, which could then be trapped by the limbs. It is difficult to conceive of W. trifurcatus digging into sediment because to engage sufficiently with the substrate the cephalon would have to tilt at an angle greater than would be allowed by movement on the posterior occipital margin. Equally, if the thorax was arched, the pygidial spines themselves would dig into the sediment.

F.) A combat device on males molded by sexual selection mediated by male-male competition for mates.  The authors consider this most likely, especially because the tridents resemble the structure of male dynastine (rhinoceros) beetles, which use them to fight for females.

Here’s a picture of three of those beetles which have similar projections as do the Walliserops trilobites (the one at the extreme right).

(From the Natural History Museum): An image comparing the different beetle morphologies as they relate to fighting mode compared to Walliserops. © Alan Gishlick

The authors did a complex morphometric analysis of body and horn shape of W. trifurcatus, comparing it with living rhinoceros beetles to see if the trident could have been used for shoveling/prying, grasping, or fencing—the three types of male-male combat seen in living beetles. The analysis puts the trilobite in the group of living rhinoceros beetles whose males fight by fencing/shoveling: jousting with the structure in front and then trying to shovel the opponent over onto its back. I won’t go into the gory statistical details, which involve principal-components analysis, but the recurved structure of the trilobite’s “trident” is similar to that of shoveling, prying, and fencing beetles (left column: observed means of fighting of living beetles; center: the cephalic structures used; right: the species name [trilobite at the bottom]).

Cephalic structures of taxa treated in this research in lateral view showing the nature of the curvature and orientation of the tip of the active weapon and how it relates to its employment in combat.


As you see, and as the statistical groupings show, W. trifurcatus is similar to the structures used in rhinoceros beetles for fencing, prying and shoveling. Here is Gishlick and Fortey’s scenario of how the males battled it out in the competition to pass on their genes:

We would hypothesize a fighting scenario in Walliserops similar to that of Trypoxylus. The trilobites would meet and at first spar with their forks, pushing and poking. At some point, they would shift to trying to slide the fork under the other, in an attempt to flip them over. Given the morphology of Walliserops, flipping would be a very effective combat technique. Although the appendages of Walliserops are unknown, it is likely that they were like those of other phacopids in not extending beyond the carapace. This is seen in the Devonian Chotecops, asteropygines Asteropyge, and Rhenops, and recently described in three-dimensional material from the Silurian Dalmanites. Once the trilobite was inverted, righting would not be a simple matter, especially if the dorsally directed spines had snagged in the sediment. An upended trilobite would probably be even more helpless than a beetle in this position and thus excluded from sexual competition.

It might also be dead!

Now the first thing that struck me when I saw this paper was the question that would have occurred to many of you: WHERE ARE THE BLOODY FEMALES??  One of the signs of male-male competition is that the structures used to compete are present in males but almost never in females, as they’re of no use in that sex—and detrimental to fitness if you don’t use them. Male deer have antlers, females do not. Body size, used for combat in elephant seals, is huge in the males, and much, much smaller in females.  So if these trilobite horns really were tools used for the “combat” form of sexual selection (the other form, as pointed out by Darwin, is female preference), the females should be around but lack the ornaments. Where are they?

Gislick and Fortey suggest that the females were indeed around, but because they lack the tridents they have not been identified as females of Walliserops trifurcata:

Since the diagnostic synapomorphy [JAC: shared derived trait] for Walliserops is the anterior trident, it would be likely that the female of the species has been classified in a different genus. That leaves two possibilities: either the females of the relevant species are at present unknown, or they are known but placed in another trilobite genus within Asteropyginae.

That mandates a search for trilobites that resemble the males but lack the horns.  The authors raise another possibility: the females weren’t preserved or were offstage, living elsewhere, but this seems less likely:

If we extend the beetle analogy further, it is possible that the females are not preserved if some trilobites, like many dynastines, engaged in sex-specific aggregations; in this case, the females were not always present in the same locations as the males, although it is difficult to explain why the latter were selectively caught up in obrution events. [JAC: “Obrution” is rapid burial in the sediments, the way these creatures must have died and been preserved.]

I favor the “females not yet found” hypothesis. There’s one more hypothesis, which is mine: both males and females have tridents.  I don’t know why this would be the case, although you could think that it’s used to take other individuals out of action in conspecific competition for food. But that makes little sense.

Finally, the authors found one example of W. trifurcatus with a deformed trident, having an extra spike (a “quadent”?). Here it is on the right. Note that the branching pattern can be asymmetrical in the normal three-pronged structure).

Examples of branching patterns for the middle tines in W. trifurcatus; A. left branching (HMNS 2020-001); B. right branching (HMNS PI 1810); C. teratological example (HMNS PI 1811) showing a secondary branching of the left-branching middle tine. Images taken from photogrammetric models. (Scale bar, 10 mm.)

Because the individual on the right was an adult, Gishlick and Fortey suggest that the deformed structure did not prevent the bearer from growing up and thriving, and thus was unlikely to be used for some vital function like feeding. This adds a little more weight to the sexual-selection hypothesis.

The Upshot:  The authors’ analyses and explanations seem plausible to me, though they’d be even stronger if they could find the females. That might be tough: in living species you could find them by looking at mating pairs or even seeing that the DNA was nearly identical, but this isn’t possible with fossilized trilobites, especially because in some living and sexually dimorphic species the females look very different from males.  If the authors are right, and I think they are, then this quote from the paper is correct:

Walliserops provides the earliest example in the fossil record of combat behavior, very likely ritualized in competition for mates. Although fossil life habits are difficult to prove, the consilience of morphology, teratology, and biometric data all point to the same interpretation, making it one of the more robust examples of paleoecological speculation.

h/t: Matthew


Gishlick, A. D. and R. A. Fortey. 2023. Trilobite tridents demonstrate sexual combat 400 Mya. Proc. Nat. Acad. Sci. USA 120 (4) e2119970120 (in press).

Readers’ wildlife videos

January 14, 2023 • 8:15 am

I wasn’t going to put up a readers’ wildlife today, as I have only about four more contributions and didn’t want to run out so soon. PLEASE send in your good wildlife photos. (I ask that they should be good, not blurred pictures of distant animals).

But today I found a two-minute video sent to me on December 15 by reader Norman Gilinsky from Washington State. Actually, it’s from a friend of Norman, but we have permission to post it.  Here’s the intro:

Here’s a wildlife video taken by my friend Thor Hansen (probably yesterday) over Padilla Bay near Anacortes in the northwest corner of Washington State. Insanely huge! These geese spend a couple of months in the agricultural fields and wetlands of Skagit County each year.

Note the V-shaped formation of many subflocks.  These are, as noted above, snow geese (Anser caerulescens). Be sure the sound is up to hear the aerial honking (and other sounds.) Can you count the geese?

More from Norman, and I do recommend reading this short piece:

Here’s a blog post I found that talks about the migration: “The amazing journal of Skagit Valley snow geese.”  Apparently the birds come from Wrangel Island, north of Siberia!

Friday biology: Oxpeckers clean a rhino

January 13, 2023 • 1:15 pm

The news is thin and what there is is depressing, including Russian claims that it’s captured the tiny salt-mining town of Soledarin in Ukraine. Although the town isn’t of strategic importance, it’s of propagandistic value to Russia, which has been losing battles left and right. (Kyiv denies that the Russians have the town.)

But let’s forget the news for a minute and watch a nice, short video of animals helping each other instead of killing each other. In this case we have a mutualism, a behavior involving interaction between two species in which each individual reaps a benefit. In this case it’s between a black rhinoceros (Diceros bicornis) and red-billed oxpeckers (Buphagus erythrorynchus).

Remember that for the behavior to have evolved on both sides (pecking and tolerance of pecking), the benefits can’t just be food and cleaning, but somehow those behaviors must have enhanced the reproductive output of individuals in each species (i.e., what used to be called “fitness” before the ableists tried to erase the term).

Note that the birds clean the ears, the lips, and even between the toes!  They clean not only wild mammals, but also domestic ones like cattle.

You might imagine, as I do, that this mutualism began with evolution in the bird, perhaps a tendency to eat insects wherever it can find them, which would already be built in by selection to get food. Over time, the boldest birds, with a genetic tendency to be braver than other birds about foraging on large, intimidating mammals, might propel the evolution of a tendency to seek those mammals out.

But of course, if it’s a true mutualism, the mammals also have to evolve tolerance of a bird pecking away at their bodies.  Have they? Well, you could in principle test whether tolerance has evolved by mimicking the pecking of a rhino with something else, but that really wouldn’t tell you the answer, for the evolution might have been to “tolerate stuff that feels like pecking”. Besides the experiment would be dangerous!

But if the rhino has evolved tolerance, that means that those rhinos who let themselves be cleaned left more offspring than those who didn’t—assuming there were genes promoting more or less tolerance. That kind of genetic variation isn’t hard to imagine, since there’s genetic variation for almost any behavior. And since insects like ticks and flies can carry parasites, it’s also easy to imagine that a peck-tolerant individual would leave more offspring than other individuals who drive away the cleaners.

Readers’ wildlife photos

January 9, 2023 • 8:30 am

Today sees the return of Athayde Tonhasca Júnior with another biology-related photo story. His narrative is indented, and you can enlarge the photos by clicking on them:

Blood, toil, tears and sweat

The Paraguayan War (1864-1870), waged by Paraguay against Argentina, Brazil and Uruguay, has a special place in mankind’s history of cruelty, carnage and devastation. Among the many horrors witnessed by combatants and observers, the episode described by Lieutenant Alfredo d’Escragnolle Taunay is particularly odd and gruesome:

“Another plague persecuted them [horses, mules and asses] relentlessly, and this singular one had disastrous effects. It came from some extremely beautiful butterflies, the so-called 88, as they appear to have that number written on the outside of their brindled wings with whimsical black-and-white drawings. However, one cannot imagine the actions of those gentle Lepidoptera, in appearance quite innocent, but in fact extremely pernicious, in all that part of Paraguay. They would huddle together in the corners of the eyes and in the nostrils of the animals, seeking any bodily moisture and soon causing such irritation at the spots where they stubbornly landed, and it did not take long to produce abundant discharge, at first of mucous and soon after copious pus! A horror! What despair from our unfortunate mounts struggling to defend themselves from the immense, flagellating legions of tiny enemies, ever more numerous and ferocious! What continuous and tiresome weaving! Unable to graze, they grew thin under our eyes and soon were completely blinded! Once on the ground, surrounded by thousands of assailants, each eye socket became a hideous and disgusting source of purulent rivers, which attracted even more the terrible butterflies. We would have surely lost all our beasts of burden and mounts, if adequate measures had not been taken, by providing them with a headband of maize straw cut into fine threads, which served as a shield to the eyes without obstructing their view.” (Taunay, 1874. Recordações de guerra e de viagem).

Caught in the maelstrom: during the Paraguayan war, horses would succumb to wounds, hunger, exhaustion, cold, and butterflies. Art by Pedro Américo (1843-1905), Wikimedia Commons:

This butterfly worthy of a Stephen King novel is the Cramer’s eighty-eight (Diaethria candrena), which ranges from eastern Paraguay to southwestern Brazil, northern Argentina, and Uruguay. Adults are often seen in orchards as they feed on rotting fruit. They also concentrate at the edge of ponds and puddles, on spots covered by ash after fires, and in bare soil soaked with livestock urine. This gathering behaviour was known by Tupi-Guarani speakers as panapaná, ‘a gang of butterflies’. For Anglophones, these butterflies are ‘mud-puddling’.

A Cramer’s eighty-eight: ventral and dorsal view © Fernanda Hisi and Geoff Gallice, respectively. Wikimedia Commons:

Butterflies mud-puddle supposedly – data are scarce – to collect salts, especially sodium. This chemical element is one of the most abundant in the Earth’s crust but occurs in minute quantities in plants because they don’t need much of it. That’s a problem for plant feeders, who require sodium in concentrations 100 to 1,000 higher than what they get in their food. Herbivores rely on their metabolism to accumulate sodium, and also on any alternative sources such as mineral licks, which are natural deposits of salts and other minerals: they are found in places such as exposed, muddy areas high in clay and organic matter. Faeces and dead bodies will do as well.

A herd of Indian bison (“gaur”: Bos gaurus) in a salt lick, and butterflies mud-puddling © Amog, and Vinayaraj, respectively. Wikimedia Commons:

Most mud-puddling butterflies are males, so researchers have suggested – again, data are lacking – that nuptial gifts are behind this behaviour. The sodium gathered by males would be passed to females during copulation and then onto the offspring, helping them cope with a sodium-poor diet. But as females of some species mud-puddle as well, there must be more to the story.

Butterflies and other insects visit mineral licks to get their sodium fix, but these deposits may not be enough for their needs. The bodily secretion of some animals – sweat – is an attractive alternative for a bold insect willing to risk being squashed by an angry host in exchange for a lick of salt. Several species in the second largest family of bees, the Halictidae, are known as sweat bees because they use perspiring people as their salt licks. These bees are harmless, but can be quite annoying with their persistent hovering and tickling.

Besides sweat, tears are an excellent source of salts, a fact enthusiastically exploited by the Cramer’s eighty-eight in Paraguay—to the chagrin of poor horses and their minders. And a surprisingly large number of butterflies, bees, flies and other insects drink tears. In addition to horses, these insects take their salty beverage from cattle, sheep, pigs, water buffaloes, antelopes and elephants; birds, crocodiles and turtles are also suitable. In Burma, India, Sri Lanka and Thailand (and probably other countries too), human beings are also involuntary tear donors to at least six species of moths. Besides the ick factor, tear-seeking insects are to be avoided because of the risk of transmission of eye diseases such as the trachoma virus and ‘pink-eye’ (conjunctivitis) in human beings (Bänziger & Büttiker, 1969).

A Lobocraspis griseifusa moth sucking tears © Bänziger & Büttiker, 1969:

As lachryphagy – from the Latin lacrima (tear) and the Greek phagos (eating, feeding) – is fairly common, Bänziger et al., 1992 proposed that there’s more to it than just sodium taking. Insects may be after amino acids and proteins, which occur in tears in fairly high concentrations. The researchers noted that tear-dinking bees rarely visit flowers or carry pollen, which suggest they may be getting all or most protein they need to raise their young from tears.

Alas, sweat and tears may not satisfy the mineral/protein needs of some insects.

Many moths and butterflies feed on extra-floral nectar, sap, or decaying fruit as does the Cramer’s eighty-eight. But some moths in the subfamily Calpinae (family Erebidae) don’t have to sit around waiting for a fruit to break open: they use their stout proboscis, which is armed with hooks and barbs, to pierce the skin of a fruit to feed on its flesh and juices. Some species in the genus Calyptra in Southeast Asia found another use for their tough proboscis: to feed on the fluids exuded by cuts, sores, scratches, scabs, and other open wounds of animals.

Distal region of the proboscis of Gonodonta bidens, a fruit-piercing moth. Lgl are legulae (rasping spines), and th are tearing hooks © Zenker et al., 2010. Journal of Insect Science 11:42

It takes a small step to go from exploring a host’s skin for an open wound to piercing it to get access to the richest bodily fluid of all – blood. Some Calyptra species have developed the ability to puncture the skin of cattle, pigs, mules, deer, antelopes, water buffaloes, elephants and rhinoceros. If these moths can pierce rhinoceros skin, they would have no difficulties with a hairless, thin-skinned primate: at least five Calyptra moths are known to feed on humans. Predictably, they are known as vampire moths.

If you want to place blood-sipping moths in the list of bizarre creatures from faraway tropical countries, think again. The vampire moth Calyptra thalictri, originally from Asia and Eastern Russia, has slowly expanded its range to northern Europe, being observed in Finland and Sweden. Watch C. thalictri having a vampirism moment, but nobody should lose sleep over it: human blood feeding by moths is harmless and extremely rare. The diet of Calyptra species comprises mostly soft-skin fruits (raspberry is a favourite), which they puncture to reach the sugar-rich juices.

Calyptra thalictri © Ilia Ustyantsev, Wikimedia Commons:

Approximately 14,000 insect species are hematophagous, that is, they feed on animal blood. Most of them are obligatorily hematophagous: they need blood as a source of nutrients and cannot survive on any other food. Some butterflies and moths, on the other hand, are facultative hematophages: blood is not vital for them, but increases their chances of survival. In the case of vampire moths, only males feed on blood. So just like for mud-puddling butterflies, male moths apparently are after sodium as a nuptial gift, which they would pass to females during mating.

An obligatory hematophagous specimen. From Archive of Dracula (1931), Wikimedia Commons:

The sodium-gathering hypothesis suggests that mud-puddling, sweat-licking, tear-drinking and blood-sucking are related behaviours. It is also notable that one morphological adaptation, i.e., a sturdy and barbed proboscis, allowed some moths to evolve from nectar-sipping to fruit- and skin-stabbing. Calpinae moths offer another example of insects’ spectacular capacity to adapt and make use of whatever nature has to offer.

Incidentally, in case you are pondering whether lieutenant Taunay – later a Viscount – exaggerated or made up his butterfly story (porkies are not unheard of in war memoirs), a similar albeit less dramatic episode was witnessed about half a century later in the vicinity of Iguazu Falls, not too far from the Paraguayan killing fields. ‘Volunteer’ horses had their eyes mobbed at night by no less than eleven species of moths (Shannon, 1928. Science 68: 461-462).

So, are equines at risk from Lepidoptera attacks in central South America? They are not. All the countries involved have changed beyond recognition since the war: much of their natural habitats have been converted to soybean fields, pasture and logging wasteland. Numbers of butterflies, moths and just about any other wild animal have plunged, some to the point of near extinction. In these inhospitable environments, the Cramer’s eighty-eight could never reach the Biblical numbers of the past, to the relief of local livestock. You may think of it as silver lining of sorts.

An eighty-eight butterfly, no longer pestering horses. In the background, the Iguazu Falls © Leoadec, Wikimedia Commons:

Readers’ wildlife photos

December 20, 2022 • 8:15 am

Today we have a biology picture story from Athayde Tonhasca Júnior. Athayde’s narrative is indented, and you can enlarge the photos by clicking on them.

To boldly go where no insect has gone before

Athayde Tonhasca Júnior

In April 2016, a birdwatcher on the Dutch coast spotted a buff-tailed bumble bee queen (Bombus terrestris) flying in from the sea. Then another bee, and another, then a wave of bees. Altogether, several hundred bees arrived at the Dutch shore (Fijen, 2020). What probably made the birdwatcher stop watching birds to count bees was the fact that as the bee flies, the nearest land eastwards is England, 160 km across the North Sea.

A buff-tailed bumble bee queen © Holger Casselmann, Wikimedia Commons:

Bumble bees have been observed flying between Estonia and Finland (80 km), England and Jersey (28.4 km), and Skye and the Outer Hebrides (24 km). So to jump from England to The Netherlands is notable, but not implausible. In fact, the seasonal arrival of bumble bee queens along the Dutch coast is not uncommon.

One giant leap for mankind, one small step for bumble bees © Visible Earth, NASA:

We know little about insect dispersal, so the occasional fortuitous observation of their long voyages amazes us. On a moonless night in 2014, a Brazilian hydrographic survey ship sailing the South Atlantic stopped over the Montague seamount to collect samples. Hull and deck lights were turned on to help the crew with their lonely task: they were 389 km from the coast and 764 km from the island of Trindade, with no other vessels nearby. Shortly after the lights were turned on, insects from all directions were flying towards the ship. Most of them collided against the hull and fell into the sea, but researchers on board captured 13 true bugs (Hemiptera), three moths and one dragonfly (Alves et al., 2019). How those insects made it that far into the sea at night and for what purpose, is anybody’s guess.

Montague seamount, anchorage site of the ship Cruzeiro do Sul (20°21′57.60″S, 36°38′46.80″W). ES: Espírito Santo State; RJ: Rio de Janeiro State © Alves et al., 2019.:

Interestingly, bumble bees flying over water bodies are often spotted because they have been following ferries, ships or sailing boats. Nobody knows why they do this: they may be using vessels or their wake as navigation aids. In any case, these observations tell us that bumble bees travel for long distances, which suggests they are migrating.

Strictly speaking, ‘animal migration’ refers to individuals traveling long distances back and forth, like many birds and mammals do. This has never been documented for insects, as no single individual completes the cycle. Instead, insects mate and reproduce along the way or at the end of the outbound journey; only their offspring travel back. But even if done in stages and by different generations, many insects migrate, sometimes in an impressive fashion. The monarch butterfly (Danaus plexippus) can fly non-stop for about 16 h over water at average speeds of 37.5 km/h, and their migratory path extends to almost 5,000 km.

Monarch butterfly migration map © U.S. National Park Service, Wikimedia Commons:

If bumble bees migrate, the consequences are profound. The ability to disperse over long distances would help solve the problem of local shortages of food or nesting sites, or unfavourable changes such as habitat degradation. It would also help bees escape parasites or other enemies. But pulling up stakes may have nothing to do with a rough neighbourhood: it could be a mechanism to increase the genetic diversity of the population.  If a new queen stays around after emergence, she has a good chance of mating with a closely related male.

Whatever the triggers, migration is a powerful survival tactic. It could explain why some bumble bee species seem to persist in hostile, intensively farmed areas. These bees may not in fact survive for long, but their numbers may be replenished periodically by new migrants.

We have just started to understand the travelling plans of our furry pollinators.

Some bumble bees may go on a journey here and there, but the marmalade hover fly (Episyrphus balteatus) is the unbeatable frequent flyer.

If you have taken a stroll in a garden or local park in Europe, you must have seen lots of flies striped orange and black hovering over flowers like tiny helicopters. These are marmalade hover flies (family Syrphidae, aka syrphid flies), which are widespread throughout Europe, North Asia and North Africa.

A female marmalade hover fly © Charles J. Sharp, Wikimedia Commons:

Adults feed on pollen, nectar and honeydew from a range of plants, while the larvae feed on aphids – entomologists say they are aphidophagous. Females locate aphid colonies by their smell and lay their eggs in the middle of them. The larvae hatch immediately, and each one devours up to 300 aphids per day until pupation. So you could say these flying morsels of marmalade are important allies of gardeners and farmers.

Some people will be surprised to know that these fragile insects embark on migrations that may cover thousands of kilometres. Each autumn, marmalade hover flies and other migratory syrphids leave Britain to spend the winter in southern Europe and the Mediterranean. Their offspring move northwards in the spring, lay their eggs, and the new generation sets out the cycle again. To survive these hazardous journeys, hover flies climb to high altitudes, where strong tailwinds take them to their intended destination.

In some years, they travel in large numbers. And ‘large’ is an understatement. By using specialised radar designed for monitoring insects (Vertical-Looking Radars or VLRs), Wotton et al. (2019) estimated that up to four billion marmalade hover flies along with the aptly named migrant hover fly (Eupeodes corollae) cross the English channel to and from Great Britain every year. This represents 80 tons of biomass. If you are impressed by these figures, you should know that hover flies account for only a fraction of insects’ latitudinal migrations known as ‘bioflows’—about 3.5 trillion insects, or 3,200 tons of biomass—migrate into southern Britain annually. Insect bioflows pour vast amounts of nutrients (particularly nitrogen and phosphorus), energy, prey, predators, parasites, herbivores and pollinators into British ecosystems. But we have only a vague understanding of their impact on food webs and local species (bioflows are also hazards to aviation: migrating insects have downed aircrafts).

The marmalade hover fly does not stand out as a particularly efficient pollinator. It is small and not very hairy, a negative mark for a member of the pollinators club because pollen transport depends on abundant body hair. Even still, each marmalade and migrant hover fly carries an average of 10 pollen grains from up to three plant species on their journey into Britain. These are not impressive figures when compared to bees, which return to their nests loaded with pollen. But considering the massive number of flies and the wide range of flowers they visit, a grain of pollen deposited on a flower here and there must add up quickly. The marmalade hover fly is known to improve the yield of strawberries, but we just haven’t paid much attention to these unpretentious pilgrims.

Don’t fly with me, let’s not fly, let’s not fly away

Insects made their first appearance on this planet between 450 and 500 million years ago. But they really took off evolutionarily – and literally – some 80 million years later when they acquired the ability to fly. From then on, insects could explore a three-dimensional world to occupy every nook and cranny of a habitat, escape predators, disperse widely and search for food more efficiently. Insects soon became the dominant creatures on Earth.

A Meganeura monyi fossil, one of the largest recorded flying insects (65-70 cm wingspan) © Didier Descouens, Muséum de Toulouse. Wikipedia Creative Commons:

The ability to fly gave insects so many advantages and opportunities that it may seem inconceivable to give up flight. And yet, many species have done just that. Brachyptery (wing reduction) or aptery (loss of wings) is widespread among insects. It is easy to understand the uselessness or even disadvantage of wings for bedbugs, fleas, lice and other sedentary creatures. But winglessness seems odd for insects we commonly see flying about such as wasps, beetles, and butterflies.

For these insects, wing reduction or wing loss almost always happens to females: males usually retain fully functional wings. The large velvet ant (Mutilla europaea), is a case in point; the male is winged and a capable flier, while the female is apterous, a trait that makes her look like an ant – hence the species’ common name. But in fact this creature is a wasp that parasitizes several species of bumble bees.

A female velvet ant © Tiia Monto, Wikimedia Commons:

The reasons for the loss of flight in insects have baffled scientists for a long time, and Charles Darwin was one of the first to come up with a theory to explain it. Intrigued by the unusual number of apterous beetles on the island of Madeira, Darwin suggested that flightlessness was a survival strategy. To avoid being blown into the ocean by the strong winds that buffet the island year round, the local insect fauna adapted by losing their wings and keeping their feet firmly on the ground.

Darwin’s theory was tested recently by Leihy & Chown (2020) with data gathered from 28 Southern Ocean Islands, a collection of isolated, wind-swept specks of land in the southern regions of the Atlantic, Pacific and Indian oceans. About half of the islands’ indigenous species are unable to fly, which is nearly ten times the global incidence of flightlessness among insects.

Number of flightless (orange) and flying (blue) insect species in the Southern Ocean Islands © Leihy & Chown, 2020:

By analyzing variables such as wind speed, temperature, air pressure, habitat fragmentation, and presence of predators or competitors, the researchers validated Darwin’s hypothesis: wind speed was the main environmental contributor to insect flightlessness. But Darwin didn’t get it quite right: the risk of being blown away is not the main evolutionary driver – after all, even a tiny island is a huge mass of land for an insect. Instead, the enormous energetic cost of flying seems to be the cause.

Indeed, brachypterous or apterous insects are more common in areas where a considerable amount of energy is required for flight such as arctic regions, mountains and deserts; or in stable habitats where dispersal is not vital for survival, such as caves, termite and ant nests, and on vertebrate hosts. Flight muscles comprise 10-20% of an insect’s body weight, and sustained flights consume a great deal of resources. If flying is not significantly advantageous, energy could be spent on some other function – such as laying more eggs, for example.

Egg production explains why winglessness is much more common in females. Free of the costs of flying, a female can produce lots of eggs, which are considerably more expensive energetically than sperm. In fact, the abdomen of many flightless females is greatly enlarged to hold as many eggs as possible. Flight is retained in males probably because it is important for finding females.

In Britain, the belted beauty (Lycia zonaria), the winter moth (Operphthera brumata) and the vapourer moth (Orgyia antiqua) are three of the better-known species with wingless females. The belted beauty is a scarce species confined to coastal areas, but the other two are abundant and widespread; the winter moth is an invasive in North America

A male and a female belted beauty © Harald Süpfle, Wikimedia Commons.

Wings were the morphological feature that assured insects’ success on Earth, but many species made a U-turn in their evolutionary road. For them, flightlessness was the best life strategy. This apparent throwback is another demonstration that evolution is not teleological, that is, it has no objectives or ‘improvement goals’. It just provides the best means for a species to adapt and survive.

Readers’ wildlife photos

December 12, 2022 • 8:15 am

Well, this doesn’t count as wildlife, but it does refer to the excretory habits of one species of primate. As contributor Athayde Tonhasca Júnior notes, ” I strongly suspect that this subject has not been approached before in your website. . . ” Indeed!  Apparently these are loo-related photos from his travels.Athayde’s notes are indented, and you can click on the photos to enlarge them.

A visit to the toilet (room), bathroom, restroom, washroom, or lavatory, is an opportunity for reflection and introspection, or to seek refuge, peace and quiet. Indeed, British men allegedly spend seven hours per year in the toilet hiding from their wives and children (according to “research” commissioned by a bathroom furniture company). But the loo – or bog, can, head, john, or latrine – can also be a place of amusement and learning.

A flamingo on duty to check your hand-washing technique in Bologna, Italy.

Unfortunately this educative and lyrical message was removed from a dentistry practice in Perth, UK:

A health warning in Scots, which is a language, a dialect or bad English, depending on who you ask (and their political views). The UK government and the European Union recognise Scots as a minority language, but many linguists place it somewhere on a dialect continuum. To the chagrin of nationalists, Scottish heavyweights Adam Smith and David Hume considered the use of Scots as an indication of poor education.

An emergency cord is great, but what if you want to order a pizza or dry your hair while bombing the bowl? (Hotel in Padua, Italy):

My travelling companion was displeased with the facilities in a Padua cafe. Squat toilets are terrible for the elderly or disabled, but they have a great advantage: you don’t need to touch anything. You learn to appreciate them when you hear the call of nature in the back of beyond. They are also better for your health, supposedly:

A latrine in the Housesteads Roman Fort, Britain, on the northernmost edge of the Roman Empire. Year 200 AC:

Marcus: Salve, Quintus.
Quintus: Ave, Marcus. Are you well? You look a bit green around the gills.
Marcus: Tell me about it. I think that batch of garum from Rome was off.
Quintus: I hear you.
Cornelius: I hear you too, Marcus. Loud and clear! Ha-ha! Say, chaps, wouldn’t you have a spare sponge on you?

A tersorium (a sea sponge on a stick) supposedly used by the Romans to wipe themselves after using the latrine. The sponge may have been washed in a gutter with running water, or in a bucket of water, salt and vinegar. But not everyone agrees with this popular tale (kids love it). According to Gilbert Wiplinger (Austrian Archaeological Institute), the tersorium may have been nothing more than a toilet brush. Read his gripping account in the Proceedings of the International Frontinus-Symposium on the Technical and Cultural History of Ancient Baths, Aachen, Germany, 2009.

Sign in a loo in an antechamber of Perth’s Sheriff Court House. One must be at rock bottom to shoot up before facing a sheriff (a Scottish judge with powers to fine or lock you up for up to five years). For the last seven years, Scotland has maintained the unenviable first place in Europe for drug-related deaths; drugs in Scotland have a death rate almost four times the rate in the UK as a whole. These figures – together with failing education, economy and health indicators – are secondary for people in power. The one-track-mind Scottish National Party cares for little else besides breaking up the union:

Epiphany inside a loo in Perth, UK:

The facilities in the family home (today a museum) of Brazilian painter Cândido Portinari (1903-1962) in the town of Brodowski, São Paulo State, illustrate a time when homes were not cluttered with stuff and had plenty of space to spare:

Collector, philanthropist and extremely rich Ema Klabin (1907–1994) needed the loo to store some of her many priceless pieces of art. Her house in São Paulo is a museum (Fundação Cultural Ema Gordon Klabin) well worth visiting. Entrance is free:

A replica of a once common warning to men in public urinals, hotels and railroad stations in the UK. Not doing-up all the buttons of your trousers (no zippers then) was a grave indiscretion:

That’s not nice. At all:

Able young non-pregnant adults can use the loo in the petrol station across the road:

In a cafe in the Brazilian coastal city of Ubatuba, you are not allowed to flush yourself. Presumably to prevent polluting the sea:

“Use the toilet as you have committed a crime: don’t leave clues behind” (loo in a São Paulo bookshop):

Wonderful documentary on the world’s woodpeckers

December 1, 2022 • 10:15 am

I watched this documentary for free at the link below (click on screenshot), and found it one of the best nature documentaries I’ve seen in a long time. It’s called “Woodpeckers: The Hole Story“, and features great biology and some fantastic video. Here’s a summary of the show from PBS:

Go deep into the woods to explore the lives of a unique avian family. Woodpeckers come in 239 species and live on every continent except Antarctica and Australia, playing a powerful role in every ecosystem they inhabit. They come in all shapes and sizes, each uniquely engineered for their particular lifestyles. Filmmaker Ann Johnson Prum (Nature: Super Hummingbirds) pecks away at what makes these birds so special through the intimate stories of woodpecker families across the world. Narrated by Paul Giamatti.

Buzzworthy Moments:

Black woodpeckers in Poland are elusive and have rarely been filmed. A pair of these large, imposing birds make a home in a beech tree, where they feed their hungry chicks.

Acorn woodpeckers love to collect acorns and “tattoo” them into the holes they create in trees. The acorns are woodpecker gold – high in vitamins, minerals, fats and protein. Placing these acorns into trees helps this food last throughout the winter.

Gila woodpeckers make their homes in cacti in the Sonoran Desert of Arizona. After carving out the nest cavity in between the spines, the Gila must wait several months for the inner pulp to dry into a tough leathery casing before moving in.

I was intrigued to learn that there are 239 species of woodpeckers, that they all form a clade long diverged from other birds, and that every woodpecker bores out its own hole for resting and breeding. (Sometimes the holes are in vertical mud cliffs.)

Now it’s possible you might not be able to see it for free (I couldn’t this morning). But you can try. Or, you can definitely see it for free if you donate to PBS, even on a one-time basis. Do try, for this is definitely worth watching!

It reminded me of a rhyme I learned as a kid:

“The woopecker pecked at the old barn door;
He pecked and he pecked ’til his pecker got sore.”

First report of “referential gesturing” in any animal other than humans

November 25, 2022 • 9:15 am

Here’s a short new paper from Proc. Nat. Acad. Sci. that, in fact, reports just a single gesture of one chimpanzee towards another. Was that worth a whole paper? Well, it appears to document the first example of “referential gesturing” in any animal other than humans.

What is a “referential gesture”? It’s a gesture that one individual could make to call attention of another individual to something, usually involving an object, an action, or a third party. (This is how humans use such gestures.) Pointing is one of these actions (you all know that when you point at something to a dog or cat, they look at your hand, not what you’re pointing at!).

In this case, one chimp held out a leaf to another chimp, and when the second chimp didn’t respond, the leaf-holder moved it towards the other’s face to call more attention to it.  Click on the screenshot below to see the paper, which has free access, and you can find the pdf here.

The behavior is connected with the way chimps groom themselves to get rid of parasites and keep themselves clean. Sometimes they also appear to groom leaves—for reasons unknown.  I’ll reproduce the report of the one gesture involving a chimp who was grooming a leaf.

We recorded an instance of a referential showing gesture between conspecifics in the context of leaf grooming in the Ngogo chimpanzee community, Kibale National Park, Uganda that seems to be produced declaratively. During self-grooming or social grooming, groomers occasionally pluck leaves that they manipulate with their fingers and mouths as if grooming them while also peering closely at them. They may be inspecting ectoparasites (e.g., ticks) they have placed on the leaves, but the function of leaf grooming remains unexplored in this community. The event described here involved a mother/adult daughter dyad. Adult female Fiona was sitting next to her mother Sutherland, whom she had been grooming. Fiona plucked a leaf from a small sapling and started leaf grooming. Sutherland’s attention was focused elsewhere while Fiona did this (Fig. 1 and Video S1), and after grooming the leaf for several seconds, Fiona held it out toward Sutherland. She repositioned her arm when the initial holdout did not elicit a response (Fig. 1). Once Sutherland attended to the leaf by fully orienting her eyes and head toward it, Fiona retracted it and continued leaf grooming.

It’s already known that chimps (and other species) use gestures to indicate what they want from others, like food or grooming, and here’s a video of such gestures:

But these aren’t referential gestures showing something to another chimp just to get its attention. As we’ll see shortly, Fiona apparently wasn’t offering the leaf to her mother to say, “here’s something for you to eat” or “here’s something we can eat”, but, according to the authors, the gesture was meant to get Sutherland’s attention, meaning roughly, “Have a look at this.” Fortunately, the gesture was filmed by the researchers, and here it is. Note how Fiona moves the leaf around until the object has Sutherland’s full attention.

The authors dissect this gesture to show that it’s truly referential:

The movements of this behavior are in line with the definition of showing or “holdouts” in human infant literature. Using the operational definitions of the most recent research on infant showing and giving, this gesture would be coded at least as an incipient show and potentially, as a fully formed conventional show. Incipient gestures are those that are plausibly part of the developmental trajectory toward the emergence of the conventional gesture form. Moreover, Fiona showed persistence with her gesturing (indicative of intentional signaling) (12), moving the leaf closer to Sutherland and more into her line of sight until Sutherland clearly adjusted her head to follow the movement of the leaf. Although Sutherland dropped her gaze to the leaf when Fiona first extended her arm, this may not have been clear from Fiona’s perspective, and head direction could have been a more reliable indicator for her. Once Sutherland had clearly seen the leaf, Fiona ceased gesturing, suggesting that the goal of Fiona’s gesturing behavior was simply to get Sutherland to attend to the leaf.

However, there are two alternative explanations for the gesture, all of which the authors find implausible (my paraphrasing):

1). Fiona was trying to share the leaf (and/or any parasites on it) with her mother as food. This seems unlikely because Fiona did not surrender the leaf to her mother. Further, chimps at Ngogo don’t eat this species of leaf. In sixty-six other observations of chimps grooming leaves near other chimps, there were no cases in which the nearby chimp took or ate any part of the leaf.

2.) Fiona’s leaf play was meant to induce some other “dyadic social activity” like grooming or playing. But chimps already show, as we see in the first video, different gestures to initiate these activities, and Fiona’s display gesture was different from these. And in 58 other observations of leaf grooming involving 30 chimps, only 5 such behavior—none showing “declarative referential gesturing”—produced immediate social grooming or play. This is the case even though three quarters of all leaf grooming events got the attention of other chimps (this was absent in the one above, making Fiona produce the referential gesture). The authors conclude:

Overall, there were no consistent differences between the leaf groomer’s behavior before and after leaf grooming, with social behaviors (social grooming, play) being more frequent before than after. This indicates that leaf grooming is not reliably used imperatively to elicit grooming or play from a partner, making it unlikely that Fiona gestured to request such an outcome.

The upshot: In my view, Fiona was indeed calling attention to the leaf (as the author say, Fiona was “sharing attention for sharing’s sake”), though we don’t know why. The fact that this is the first time such a gesture has been observed despite chimps being observed for decades AG (“after Goodall”) also suggests that referential gesturing is not common in this species. Perhaps it occurs only under very special and specific conditions, but we’ll need a lot more observations to reach this conclusion.

However, if we do find that referential gesturing in chimps is part of their behavioral repertoire, it leads to one inference, an inference that was the subject of Darwin’s book The Expression of the Emotions in Man and Animals (1872). Darwin found (or thought he found) similarities in how humans and other species express emotions, leading him to conclude, as part of his Big Game Plan, that our emotional expressions evolve from precursors present in our common ancestors with other species, and that other living species have inherited expressions resembling ours from those ancestors.

In this case, it’s not really the expression of an emotion that Fiona shared with humans, but a referential gesture. But the implication is the same. As the authors say, the analogy to human behavior is critical here:

Several aspects of the Fiona–Sutherland interaction provide hints as to where such future research may find further examples of showing and other protodeclarative gestures in one of our closest living relatives. . . Additionally, Fiona was interacting with her mother, with whom she shared a close social bond. Our observation suggests that in highly specific social conditions, wild chimpanzees, like humans, may be motivated to communicate cooperatively and share interest and attention simply for the sake of sharing. If so, this raises the question of whether differences between humans and chimpanzees in the ability to engage in cooperative communication are quantitative rather than qualitative, with ramifications for our understanding of the evolution of human social cognition.

I presume, though, that animals like cats and dogs could be trained to respond to referential gestures. (They’re already trained to make them to humans, like pointer dogs assuming a stance pointing to human prey.) Has anybody trained of observed their pets respond to a referential gesture, like looking at something you’re pointing at rather than at your hand?

The remarkable physiology of hibernating bears

October 11, 2022 • 10:45 am

Have you been voting in Fat Bear Week? If not, today is the final day: the run-off between two heavyweights that will determine the Fattest Bear.

You probably realize that the bears get so fat in the fall because they are about to go into five months of hibernation, and need to stock up on food to sustain their metabolism as they go into winter. The Washington Post article shown below describes the remarkable phenomenon of hibernation, the potential bodily problems it poses, and new biochemical discoveries that help the bears obviate these issues and could also help immobile humans with the issue of atrophied muscles. Click to read:

Quotes from the article are indented:

But for many scientists, the true fascination of Fat Bear Week involves what happens next, when the now beachball-shaped bruins, carrying about 40 percent body fat, lumber into their dens and start hibernating. During hibernation, they remain healthy under conditions that would weaken and sicken mere humans. The bears emerge months later, lean, strong and barely affected by their months of starvation and inactivity.

Until recently, researchers could not explain how. But several fascinating new molecular studies suggest hibernation remodels bear metabolisms and gene activity in unique and dramatic ways that could have relevance for people. The fat bears can advance our understanding of diabetes, muscle atrophy, inactivity and the ingenuity of evolution.

Superficially, hibernating bears seem passive and inert. For five months or more, they do not eat, drink, urinate, defecate or move, except occasionally to turn over or shiver. Their metabolisms drop by about 75 percent. Hearts beat and lungs inflate only a few times a minute. Kidneys shut down. The bears grow profoundly insulin resistant.

If this were us, we would shed much of our muscle mass because of inactivity and probably develop diabetes, heart disease, kidney failure, frailty and other ills.

But the bears maintain their muscle and rapidly reestablish normal, healthy insulin sensitivity and organ function after hibernation.

Insulin functions to allow cells to absorb glucose from the blood to use as energy, or to convert some glucose to fat. It also helps break down fats and proteins. Normally, the onset of insulin resistance would, as the article implies, lead to diabetes and its attendant problems, but the bears are somehow able to tolerate that—as well as the muscle atrophy attendant on not moving for five months. (Muscle atrophy is a problem for people who are either paralyzed or bedridden for long periods of time.)

How do the bears do this? That’s the point of the article, which links to three scientific articles (one given below) explaining how the bears survive hibernation.

The information on fat usage came from blood samples drawn from hibernating and non-hibernating bears at Washington State University (WSU), bears trained to allow a blood draw without being anesthetized. (I guess the WSU bears also go into hibernation.)

It turns out that there is differential activation of genes in the bears during hibernation that protect them from deleterious effects of hibernation. Here are two papers cited:

By comparing the samples, [reserachers] concluded hibernation is biologically uncanny but hardly quiet. In a 2019 study, the WSU scientists and others found more than 10,000 genes in bears that work differently during hibernation vs. in autumn or spring. Many involve insulin activity and energy expenditure and most occur in the animals’ fat, which becomes quite insulin resistant during hibernation and robustly insulin sensitive immediately afterward.

Digging deeper into that process for a new study, published in September in iScience, they bathed fat cells drawn from hibernating and active bears with blood serum taken during the opposing time and watched the fat switch seasons. Fat from hibernating bears became insulin sensitive and genetically similar to fat from the active season and vice versa.

In other words, something in the blood serum of non-hibernating bears restored the insulin sensitivity of hibernating bears, and vice versa. This shows that it is something in the serum, and not in the fat, that changes during hibernation. The article continues:

Perhaps most compelling, they also identified and cross-matched hundreds of proteins in the animals’ blood and found eight that differed substantially in abundance from one season to the next. These eight proteins seemed to be driving most of the genetic and metabolic changes in the fat.

Of course correlation is not causation, and I doubt that 10,000 genes are involved in actually producing hibernation or mitigating its effects. (After all, humans have only about 25,000 protein-coding genes—more if you include as “genes” bits of DNA that do something but don’t produce proteins—and bears can’t differ that much from us. There may be changes in that many genes, but many of these may simply be side effects of natural selection changes the expression of many fewer genes.

But it’s clear that genes involved in insulin usage and sensitivity work differently in hibernating versus nonhibernating bears. What are the cues that turn these genes on and off? I doubt that we know, and the paper doesn’t say, but a good guess is that this has to do with environmental factors indicating the impending arrival of spring or fall: cues based on day length or temperature.

But what about the bears’ muscles? Why don’t they atrophy? Again, it’s due (as it must be) to differential activation of genes. And again, the gene products responsible seem to be circulated in the blood serum.

The paper below from PLoS ONE (click on screenshot to read; pdf here and reference at bottom), implicates both the blood serum and the genes involved in maintaining muscle.

The Japanese researchers bathed cultured human skeletal muscle cells in serum from either hibernating or non-hibernating black bears. What they found was significantly less degradation of protein when hibernating-bear serum was used. This appeared to be based on a gene-induced decrease in levels of two proteins and an increase in the level of another, which act in concert to preserve protein levels in the cultured cells. (The protein made in reduced amount breaks down muscle while the others promote and sustain muscle growth.) Altogether, changes in gene action appears to keep the bears’ muscles fairly intact as they go through hibernation.

Now these are cultured human cells, not bear cells, and the experiment was done in vitro rather than in vivo, but it gives a very promising lead to how bears keep their muscles strong during hibernation.

The Post article also lays out the potential uses of this information in human health.


Potentially, these same eight proteins, which also appear in human blood, might at some point be harnessed pharmaceutically to improve insulin sensitivity or treat diabetes and other metabolic disorders in people, Kelley said. But that possibility lies far in the future and requires vastly more research with bears and us (although perhaps not in close proximity).


The ultimate aim of this research, [author] Miyazaki said, is to isolate and refine all of the substances and processes in hibernating bears’ blood and elsewhere in their bodies that protect them from muscle wasting, with the hope that these same elements might treat atrophy from bed rest or aging in people.

“There is probably no better way to maintain a healthy lifestyle than through physical exercise,” he said, but for people who cannot be active, for whatever reason, the internal operations of slumbering bears might someday provide respite from frailty.

It’s important to remember that these remarkable changes are certainly due to evolution via natural selection, as it’s hard to imagine a random process like genetic drift causing evolutionary changes that are certainly adaptive.

As Ernst Mayr emphasized, many important evolutionary changes in animals begin with a change in behavior. Perhaps bears in cold areas survived better if they underwent a period of low activity during winter when food is scarce (this behavioral change could reflect genetic variation), and then those quiescent bears who also had mutations affecting fat and muscle metabolism would be those most likely to survive hibernation, leaving their genes to future bear generations.


Miyazaki M, Shimozuru M, Tsubota T. (2022) Supplementing cultured human myotubes with hibernating bear serum results in increased protein content by modulating Akt/FOXO3a signaling. PLoS ONE 17(1): e0263085.