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.


Baby elephant and mom get stuck in the mud, but are rescued by “first responders”

January 22, 2023 • 1:00 pm

If this video doesn’t make you tear up, you have a heart of stone!

This was a really dicey situation: a female African elephant gets badly stuck in the mud, and her baby, refusing to leave her side, gets stuck, too. It takes a bunch of people, a tractor, two trucks, and some anesthetic to get her free. In the end, all is well!

The YouTube notes from We Love Animals:

Baby elephant saved from muddy pit keeps running back to his mom’s side – but she’s still trapped, shoulder-deep, in the mud 🐘❤️

How did Mom get trapped in the first place?

Readers’ wildlife photos

January 19, 2023 • 8:15 am

Today we have some Alaska critters from reader Simon Hayward. His notes are indented, and you can click on the photos to enlarge them. This is the first part of two batches of photos.

Some pics from Denali National Park and Preserve (mostly).

Caribou [Rangifer tarandus, known as reindeer in Eurasia] Look at the antlers on this guy! Also caribou poo and food [below] – the whiteish caribou lichen forms a good part of their diet.



Grizzly bears from Denali [Ursus arctos horribilis]. I tried to include a short iPhone movie of a bear (4-5 yr old male (I was told – the one in the last bear photo here) digging for tubers. Won’t attach to an email – too big.

These bears exist largely on berries supplemented with tubers, ground squirrels and the odd tourist

This tree has been used by a bear to rub off some of its winter fur during the spring moult (my laptop wants to spell check that to molt – apparently it’s an English/American spelling difference. Still learning them after 30+ years).

Grizzly bear poo in Denali in late summer. Note the huge number of berry seeds (grad students get to sift and count these); a bear eats around 200,000 berries per day here to fatten up for winter. The rivers in the park are all glacier-fed and contain too much glacial silt for fish to survive. As a result the bears in central Alaska are smaller than their salmon fed coastal cousins.

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 7, 2023 • 8:15 am

Send in your photos! I am sweating blood!

Two batches today: stars ‘n’ squirrels.  First, the three star photos come from Tim Anderson.  Click the photos to enlarge them:

M42, the Orion Nebula:

NGC3372, the Carina Nebula and NGC3532, the Wishing Well Star Cluster

And squirrel photos from Mary Barbara Vance Wilson:

I hit the cute diurnal squirrel trifecta at Collier State Park in Klamath County, Oregon, earlier in September 14Golden-mantled Ground Squirrels (Callopermophilus lateralis) are common sights in western parks.  These were busy stashing food for the winter.  They are often confused with chipmunks, which are smaller and have facial stripes.
The Yellow-Pine Chipmunk (Neotamias amoenus), one of the smallest chipmunks, were dashing so fast across the ground, up tree trunks, and over historic logging machinery that getting a photo was difficult.
The Douglas Squirrel  (Tamiasciurus douglasii) is only about as big as the ground squirrels but lacks stripes except for a short bar on the side.  It spends more time in the trees than the other two.

Readers’ wildlife photos

December 30, 2022 • 8:15 am

Today we have some exotic travel photography by reader Stephen Warren. His notes are indented, and you can enlarge the photos by clicking on them:

Some nature pics from deep in the Mauritanian desert, earlier this month.

We took 11 camels carrying water, tents, mattresses, and food including (look away now if you are squeamish) a live goat. Everyone walked, including the chameliers (camel drivers), and it was good hard exercise in the dunes. Here the caravan sets off:

Camp pitched on day 1. This is the main tent, the sleeping quarters for the guide, cook and 4 chameliers. The camels (two in the background) are free to roam, to feed, but are hobbled and don’t wander far from the camp:

Here you see Limam, one of the chameliers. In the background you see the `sand sea’, the high dunes up to 40 or 50m high. Forget fancy desert boots. The chameliers are the experts and they wear cheap flipflops. The idiot intrepid adventurers instead spent a great deal of time emptying sand from their shoes and socks:

A closeup of the same large dune. This is the leeward side, looking N, the persistent wind direction being E to W. So on the leeward side the blown sand falls at the critical slope, set by the inter-grain coefficient of friction (the slope is gentler on the windward side). The dunes are about 1km across and repeat in waves. The greenery, ’sbot’, is the camels preferred food, and was abundant for our trip due to unusually heavy rain in October. The tree is an acacia:

The wind creates beautiful patterns in the sand:

. . . which are then marked by tracks from a variety of wildlife including fox, hare, gerbil, snake, lizard, scorpion, and beetle. We saw all of these creatures except gerbil and snake, but we did see their tracks. Here is a wonderful array of tracks, dominated by scarab beetles:

The next one is from a gerbil. I’m guessing that because they jump, the rear paws are the two separate  paws, and the front (leading in landing) paws are the two together, but I didn’t see it in action:

Lizard prints: running on the left, then stopping, turning and walking on the right, trailing its tail:

Here are the intrepid explorers in a scene reminiscent of Tintin in The Crab with the Golden Claws:

. . . complete with camel bones (if you know the book):

Finally, treasures found in the desert. The region was populated by humans until about 6000y ago and there is debris from this civilisation everywhere to be found. On the left, firstly 3 arrow heads, and below that two scrapers, perhaps for separating hide from flesh. The ends are filed to a sharp edge. The material looks like a type of chert.Top right is a small meteorite I found, a chondrite. The desert is a great place to look for meteorites. Below that are what appear to be two fossilised eggs that we bought from a chamelier – any ideas, readers? They are about 5cm long and are perhaps from a small dinosaur. I have sent a photo to the Natural History Museum in London asking for help in identification. The bottom white item is a piece of ostrich egg shell. This is a common find in the region suggesting that ostriches were farmed in those times:

Readers’ wildlife photos

December 27, 2022 • 8:15 am

Well, I calculate that I have about three days’ worth of wildlife photos left, and then this feature will either close or become sporadic. Please send in your photos if you want to keep this feature going. Thanks!

Today we have a batch of photos from ecologist Susan Harrison. Her captions are indented. and you can click the pictures to enlarge them.

Ditches, Puddles, and Ponds  

Recently there have been several nice drenching rainstorms in northern California.  We need a lot more to end the severe drought.  Still, it’s heartening to see the fields fill with puddles and the ditches fill with runoff, since standing water brings the landscape to life with animal activity. Almost all of the scenes below are from the Central Valley around Davis in November-December 2022.  The tidbits of information are mostly from Cornell Lab of Ornithology’s All About Birds website.

Wilson’s Snipes (Gallinago delicata) have eyes set so far back that they can see almost 180 degrees. Combine that with their stripy camouflage and zigzaggy flight, and hunting Snipes would require one to be a skillful… sniper… which is where the latter word comes from:

American Pipits (Anthus rubescens) are delicate birds that bob and wag their tails while hunting in standing water for aquatic insects, and they are much easier to hear than see as they fly around saying their name.

Soras (Porzana carolina) are found throughout the Americas, but the Central Valley is one of their few year-round locations.  It seems amazing that such round, stubby-winged birds can actually migrate between North and South America.

Pied-billed Grebes (Podilymbus podiceps) control their buoyancy by trapping water in their feathers.  This one is in the process of vanishing downward like a feathered submarine.

North American River Otters (Lontra canadensis) were rare here until recently, but have made a remarkable comeback thanks to waterway cleanup and protection from hunting. They somehow travel overland to reach just about any fish-containing water body, even the UC Davis duck pond.  This one is in a ditch in farmland.

These three juvenile Raccoons (Procyon lotor) were foraging together in a wet ditch when an intruding birdwatcher sent them into a defensive huddle.

Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) jostle for territory in reed beds with the much commoner, but smaller, Red-winged Blackbirds (Agelaius phoeniceus) and the tiny Marsh Wrens (Cistothorus palustris).

Marsh Wrens (Cistothorus palustris) are fierce little devils that will fight with larger birds.  They also pierce eggs and kill nestlings of their own and other species.  If you play their call they will come out spoiling for trouble.

Belted Kingfishers (Megaceryle alcyon) make a raucous rattling call as they zip over streams and ponds looking for fish.  They nest in streambanks, and their breeding range has expanded thanks to human-made embankments like road cuts and gravel pits.

There must be a lovely, elusive Common Yellowthroat (Geothlypis trichas) hiding in the reeds somewhere nearby if you hear their wichety-witchety-wichety song or their chuck! call.

Black-crowned Night Heron (Nycticorax nycticorax) live in colonies around ponds and marshes, and eat almost anything they can their beaks around – worms, insects, crayfish, mussels, fish, amphibians, reptiles, rodents, birds, and eggs.  To atone for the heron misidentification in my last post, here are an adult and an immature Black-Crowned Night Heron, photographed at Lindo Lake County Park in San Diego where they are rather used to humans.

Black-crowned Night Heron, immature:

Readers’ wildlife photos

December 26, 2022 • 8:15 am

As we approach 2023, a year closer to our appointment with the Grim Reaper, I ask readers to send in their good wildlife photos. Must I beg? Very well, then: pretty please!

Today we have the second part of the batch of photos sent by reader Kevin Krebs (part 1 is here). He notes that the photos were taken in and around Vancouver, B.C., where he lives. All are birds save one cute mammal at the end.

Kevin’s notes and IDs are indented, and you can enlarge the photos by clicking on them.

Common Raven (Corvus corax)

Present across most of the northern hemisphere, Ravens have been heavily burdened by human myth, superstition, and persecution. They also have a close relationship with wolves, spotting carrion or prey, and calling to alert wolves so they can procure the scraps. This is a member of a small family that lives in a local park. And to answer the perennial question many birders must field: How to tell a Raven from a Crow.

Belted Kingfisher (Megaceryle alcyon)

Distinctive and vocal birds, Belted Kingfishers can be found by streams and lakes across most of North America, attentively perched on a branch overlooking the water. Once they spot prey, they dive straight into the water to catch their meal, quickly flying back to beat and consume them:

Brown-headed Cowbird (Molothrus ater)

One of the tips for a good bird photograph is getting as close to their level as you can. I ended up lying down in the grass to get a photo of this juvenile Brown-headed Cowbird. Cowbirds are obligate brood parasites, meaning they must lay their eggs in the nests of other birds, and those birds raise their chicks.  This behavior doesn’t make them popular with humans, who often can’t help but project their moral beliefs onto them.  They do, however, raise a fascinating question: How do you know you’re a Cowbird if you’ve been raised your entire life by a Song Sparrow?:

California Quail (Callipepla californica)

A male California Quail keeping watching and calling to his flock. These ridiculously cute and social birds are native to the west coast of the USA. I photographed this bird in Keremeos, British Columbia, at the northern edge of the California Quail’s range:

Western Tanager (Piranga ludoviciana)

A vibrant and eye-catching warbler that migrates through Western North America. These birds can be a challenge to find, spending much of their time in the shadows of deep foliage. Surprisingly, male birds like this one can’t produce the red pigment found in their feathers, and it isn’t entirely clear where they acquire it from. The leading theory is an insect, which in turn gets the pigment from a plant:

Brewer’s Blackbird (Euphagus cyanocephalus)

Originally a bird of open lands in Western North America, the 20th century saw the Brewer’s Blackbird spread eastwards, taking advantage of ever-increasing open habitats created by agriculture and forestry. The males are hard to miss with their glossy irridescent plumage and piercing yellow eye:

Yellow-headed Blackbird (Xanthocephalus xanthocephalus)

In the running for the most succinctly named bird, the Yellow-headed Blackbird breeds in marshlands throughout central and western North America. Conspicuous in both plumage and song, these birds are highly social and congregate in large flocks after breeding to winter in the southern United States and Mexico:

Killdeer (Charadrius vociferus)

A large plover found throughout North and Central America, named after a somewhat creative interpretation of their call.  Like many plovers, Killdeer exhibit false brooding — sitting on ‘imaginary’ nests to confuse predators.  They are perhaps more known for their broken-wing display, when they feign injury to draw predators away from their nests.  If you ever encounter a Killdeer behaving this way it means you’re too close to their nest! Turn around and walk away slowly, keeping a close eye on the ground:

American Avocet (Recurvirostra americana)

Avocet are large wading birds with a unique upturned bill with which they scythe through muddy wetlands to capture food. Like so many birds and animals, they are increasingly threatened by the destruction and reclamation of wetlands:

Yellow-bellied Marmot (Marmota flaviventris)

Central southern British Columbia is the northern limit of the range for these marmots, also known as Rock Chucks. I usually stick to photographing birds, but these chubby rodents were too cute to resist. Yellow-bellied Marmots start hibernating in September, so this individual will be deep asleep in a warm burrow right now.

Readers’ wildlife photos

December 24, 2022 • 8:15 am

We have a few odds and ends today in the runup to the Big Holiday.  Click the pictures to enlarge them; readers’ captions are indented.

First, some ducks from Steve Barnes.

These are a handful of photos taken around Bellingham and Birch Bay, Washington, during my brief time with a Sony DSLR some years ago.  I presume these are mallards (Anas platyrhynchos), and similarly presume confirmation or correction will be near-reflexive on this site.

From Bill Robertson:

Eastern Gray Squirrels (Sciurus carolinensis) will go to great lengths to subvert squirrel-proof bird feeders. This individual jumped about 3 feet (≈ 1 m.) from another feeder with peppered seed mix to get to this one. It was snowing the first day, and then the next day was quite pleasant, and the noshing was apparently quite agreeable.

The next night I surprised a raccoon reconnoitering the possibilities, so now I bring this one in overnight.

The American Goldfinch (Spinus tristis) is not particularly sharp–I fear it may not meet your accustomed standards–but he apparently feels the same way I do about the snow.

Bill also sent two photos of Turkey vultures: (Cathartes aura)

I use a Sony a7RIV, with a Sony 200-600mm zoom, and for these a 1.4x teleconverter as well.

. . . and from Reese Vaughan:

Gulf Fritillary, Agraulis vanilla, in the remains of my Passion flower vine.

Readers’ wildlife photos

December 23, 2022 • 8:15 am

If you’re idle during the holidays, do send in some photos. I ain’t going to Poland, so the feature can continue—if people contribute.

Today we have the third batch of photos from Rosemary Alles (part 1 is here and part 2 is here), featuring the creatures of South Africa. As I posted before:

Today’s photos come from Rosemary Alles, who lives in South Africa and works for a conservation organization that partners with local people. Her narrative and captions are indented, and you can enlarge the photos by clicking on them. This is only part of a larger set: more photos will come later.

I am an American living (temporarily) in SA. These pics were taken from my small studio in rural South Africa and while within the greater Kruger region. I am originally from Sri-Lanka, a war-torn nation just to the south of India. My family and I immigrated to the west to escape a violent civil war in Lanka.You can find more about us (the work our org does) here. We focus primarily on indigenous women/children at the intersection of conservation.

Click on the photos to enlarge them.

Two photos of a male duiker antelope (JAC: either red or gray; I don’t know):

Male Lowland Nyala antelope (Tragelaphus angasii):

Male subadult nyala:

Nyala calf:

Saddle-billed stork (Ephippiorhynchus senegalensis):

Southern masked weaver (Ploceus velatus):

Unidentified sparrow:

Sunset, Manyeleti Reserve:

Vervet monkey (Chlorocebus pygerythrus):

White-backed vulture(Gyps africanus):

African Wild dog (Lycaon pictus):

Emerald-spotted wood doves (Turtur chalcospilos) on termite mound: