Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
Please send in your good wildlife photos, folks. The tank is dropping at a disturbing rate.
Today we’ll feature the second half of Daniel Shockes’s photos from Africa (part 1 is here). His narration is indented, and you can click on the photos to enlarge them. Here’s his original introduction:
Here are photos from our trip to Africa. Started in Livingstone Zambia, traveled through Zimbabwe, and into Botswana.
Male Lion after a kill. This group had just taken down a baby elephant and was methodically eating it. I do have pictures of them eating the carcass but even dispassionate scientific readers might find it a bit disturbing. Happy to share more if you want (also have great video):
We have a special bonus today: DUCKS AND DUCKLINGS! At my request, UC Davis ecologist Susan Harrison took photos and video for this site when she went out yesterday to help a colleague band, chip, measure, and DNA-sample wood ducklings. Susan’s narrative is indented; click the photos to enlarge them.
Notes From a Wood Duck Research Field Trip
In early June 2023, I accompanied UC Davis’ John Eadie, a leading expert on waterfowl biology and conservation, to measure and tag newly hatched Wood Duck (Aix sponsa) ducklings.
For ten years, John and his collaborators have been studying the social lives of Wood Ducks, especially the striking behavior called nest parasitism. Females (‘hens’) may lay some or all of their eggs in the nests of other Wood Duck hens. Why do they do this? It’s probably related to the fact that they nest in tree cavities, which are a scarce resource. But how do hens decide whether and whom to parasitize? What determines the shifting benefits of raising your own kids versus trying to get them raised by someone else? You can read this lively and beautifully illustrated American Scientist article to find out what’s been learned and what’s still unknown.
We went to a private ranch near Davis where John and his lab have set up 100 of their 400 total nest boxes. Nest boxes help boost Wood Duck populations, and when suitably equipped, they also make it easy to collect data on hens and ducklings.
These ‘research’ nest boxes can be raised or lowered for access, and are equipped with instruments that read the output from tiny radio tags similar to pet microchips:
The first step is to lower and open the nest box to see if the eggs have hatched:
Then the entrance hole is covered to keep the hen inside and the ducklings are carefully extracted:
Each duckling is brought to a mini-lab on the truck tailgate:
Being a good mentor, John is letting me ‘help;’ here I’m holding my first duckling:
Ducklings are slid headfirst into the tube to be weighed:
Bill length, bill width, and tarsus length are measured:
A tiny pinprick allows blood to be drawn for DNA analysis:
A radio tag the size of a rice grain is gently and safely slid under the skin:
Foot color is recorded as tan (left), orange (right), or pure black, since John is curious about this variable trait:
Ducklings then go back to their nest and the seemingly calm hen. Using this combination of radiotagging and DNA, John and collaborators have collected around 3 million data points, each one a combination of an individual duck’s identity, parentage and location. These data have shown, for example, that a hen’s tendency to parasitize is pretty strongly correlated with her mother’s tendency to parasitize.
We stopped at John’s aviary on campus. Here I’m holding Konnie, a Wood Duck hen who was hand-reared and named for Konrad Lorenz, to show off her gorgeous iridescent wings:
In this brief video, Konnie and her mate Crookneck like they are eating but they are actually performing a contact ritual, watched by a Mallard (Anas platyrhynchos). Turn the sound up to hear their squeaky calls and John explaining their behavior. He says many pair-bonding behaviors in birds are ritualized versions of feeding: (Photo 13)
This male Cinnamon Teal (Spatula cyanoptera), less friendly than Connie, energetically nibbled at fingers when picked up:
It was great fun comparing notes with John about research. When I was in grad school learning plant and insect ecology, it was often said that you couldn’t really test theory using birds or wildlife, because you couldn’t do experiments or get large amounts of data. But sensor and DNA technologies have since transformed the study of animals in the wild. And with Wood Ducks, a researcher can deploy their most critical resource – nest boxes – and return later to find abundant and accessible study animals. However, since adult male Wood Ducks are hard to catch and tag, their role in the social network is not yet well understood.
Send in your photos, folx! I need seven batches a week to keep this going (and thanks to those who heed my calls).
Today we have several contributors, the first being reader Don Bredes. All contributors’ words are indented, and you can enlarge the photos by clicking on them:
Our rose-breasted grosbeaks (Pheucticus ludovicianus) showed up here in northern Vermont this past week. They perch on the deck railing, chirping for us to come out and feed them a few sunflower seeds and waiting, trustingly, right there. We’ve seen only males so far. They remember us, clearly. Rose-breasted grosbeaks can live in the wild for 10 years or longer, twice as long in captivity.
In the fall they migrate from their breeding grounds in North America to Central and northern South America. Most fly across the Gulf of Mexico in a single night, although some migrate over land around the Gulf. Their population globally, now at 4,700,000, is dropping slightly. In their wintering grounds, they are commonly trapped for sale as caged birds because they’re beautiful, and their song is lovely.
We can’t help but wonder about the little neighborhood in Belize or Venezuela where “our” grosbeaks spend their winters and whether another family there may have befriended them.
From Peter, a poisonous juvenile Dugite snake (Pseudonaja affinis) gets killed by a Redback spider (Latrodectus hasselti). He added this:
Two decades ago I took a photo of a redback spider that had killed a small lizard. This is next level up.
A video from Rick Longworth, who says he’s put up a new house for the displaced wood ducks:
Today a pair of wood ducks (Aix sponsa) inspected my duck box for nesting. Unfortunately for them, a Western screech-owl (Megascops kennicottii) had already taken ownership and was sitting on eggs. The woodies both inspect the box and look down the back side where the opening is. The male—the one wearing the tuxedo—looks on as the female makes attempts to enter the hole. Imagine her shock to see two enormous, yellow eyes staring back. Suddenly, a different female shows up. The male is pretty upset and tries to intimidate the interloper. The original female gives up and scurries off. Soon the male leaves too. Music is Kevin MacLeod ~ Fluffing a Duck.
Fortuitously, when I hadn’t prepared any posts for today that require my neurons to work, reader Athayde Tonhasca Júnior came through with one of his patented text+photo stories, this time a fascinating one about how opportunistic natural selection can create predator/parasite niches within niches in completely unexpected and astonishing ways. This hierarchy was wonderfully expressed in the short poem “Siphonaptera” (the order in which fleas are placed) by British mathematician Augustus De Morgan:
Great fleas have little fleas upon their backs to bite ’em,
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn, have greater fleas to go on;
While these again have greater still, and greater still, and so on.
Athayde’s text is indented, and click on the photo to enlarge them.
The body snatchers
by Athayde Tonhasca Júnior
Family feuds abound in history and in the tabloids, but things got really out of hand with the offspring of Egyptian gods Geb (Earth) and Nut (sky). As the first-born, Osiris was naturally chosen to be the ruler of the world. But his brother Set didn’t care one bit for this undemocratic arrangement, so he decided to despatch Osiris to the Underworld. So he set out a murderous plan worthy of an Agatha Christie story. Set first commissioned a beautiful casket, tailored to fit a body with Osiris’ exact measurements. Set then organised a magnificent banquet, inviting heavenly celebrities and bro Osiris. When they were all done with the eating and drinking, Set announced a surprise. The casket was brought in, and the host told his guests that whoever could fit inside, could take it home (an odd gift to us, perhaps, but who are we to judge Egyptian gods?). One by one the guests climbed into the casket, which was too small or too big – until Osiris had a go at it. He laid down inside the casket, which, to his glee, fit him perfectly. Set’s trap was set; he slammed the casket’s lid shut and locked it, killing his sibling. Later Set retrieved Osiris’ body and chopped it into small pieces.
The Mummy (1932) escaped from his sarcophagus, but no such luck for Osiris. Art by Karoly Grosz, Wikimedia Commons:
Set’s shenanigans were the perfect inspiration for naming a new species from the genus Euderus, a small group of parasitic wasps in the family Eulophidae. Most Euderus species are moth and beetle parasitoids, but the wasp discovered by Egan et al. (2017) in Florida (USA) is peculiar, to say the least. Its host, Bassettia pallida, is itself a parasitic wasp, but of a different kind: this species is one of the many gall wasps or cynipids (family Cynipidae), which lay their eggs in oaks (Quercus spp.) and less commonly in related plants (family Fagaceae). The egg-laying induces the plant to produce a gall, which is an abnormal growth resulting from increased size or number of cells (galls can also be caused by tissue feeding or infections by bacteria, viruses, fungi and nematodes). Cynipids trigger their host plants to produce nutritious tissue inside their galls, which become ideal places for a larva to grow: there’s nothing better for one’s survival than a cosy, safe and nourishing nursery.
In the case of B. pallida, it induces the formation of galls inside stems of sand live oak (Q. geminata) and southern live oak (Q. virginiana). Each of these galls is called a ‘crypt’. So appropriately, B. pallida is known as the crypt gall wasp. When the adult wasp completes its development, it chews an exit hole from inside its woody quarters and flies away.
Life looked good for the crypt gall wasp in the southeastern United States—until we learned about the machinations of its recently discovered enemy. The Eulophidae parasitoid locates a crypt and pierces it with its ovipositor, laying an egg inside the chamber, near or into the developing crypt gall wasp. We don’t know exactly what goes on inside the chamber, but the outcome is not good at all for the crypt gall wasp. When it tries to chew its way out, it’s no longer able to create a hole big enough to fit its body: the wasp becomes entrapped inside its crypt, Osiris-like. During its failed attempt to get out, its head blocks the exit hole. All the better for the parasitoid larva that hatched inside the crypt: it can feed at leisure on the host’s weakened body. On completing its development, the adult parasitoid wasp chews through the host’s head plug and comes out to the big wide world. So there was no better name for this species than Euderus set, the crypt-keeper wasp.
JAC: Isn’t that an amazing story? I’m sure we don’t know how the parasitoid disables the gall wasp in this way. Imagine the genetic changes involved in this complex evolution, involving the parasitoid’s egg-laying and multiple behaviors of its larval stage. But that’s a passing expression of amazement; let’s continue with Athayde’s tale:
The relationships between oaks and these wasps are examples of host manipulation, which happens when a parasite influences the host’s behaviour or physiology to its (the parasite’s) advantage. The crypt gall wasp induces its host plants to produce galls for its benefit, and in turn the crypt-keeper wasp forces its host into becoming trapped and an easy meal for the parasitoid’s larva: the manipulation of a manipulator is known as a hyper-manipulation, an uncommon phenomenon.
There are many cases of host manipulation, and the zombie-ant fungus described by the co-author of the theory of evolution by natural selection Alfred Russel Wallace (1823-1913) is one of the better known. This fungus (Ophiocordyceps unilateralis) induces its host ants to climb up the vegetation and clamp their mandibles around a twig or leaf vein. An infected ant will stay put, rain or shine, while the fungus grows inside it. After 4-10 days the ant dies, the fungus grows a ‘stalk’ (stroma) from the ant’s head and releases spores that will infect ants walking about on the forest floor.
The more researchers look into it, the more they find cases of host manipulators such as the Darwin waspsHymenoepimecis spp., which parasitize several species of orb-weaving spiders in the Neotropical region. A female wasp stings and temporarily paralyses her victim, laying an egg on its abdomen. The emerging larva bites through the spider’s cuticle and feeds on its ‘blood’ (haemolymph). The spider carries on with its life, building webs and catching prey, but the growing parasitoid takes its toll; eventually it kills its host.
But shortly before the spider’s demise, somehow —probably by hormone injection—the larva takes command of the host’s behaviour. The spider builds a cocoon web made of thickly woven silk, which doesn’t look at all like a normal web. The spider dies, the larva enters the cocoon and completes its development. Some days later, the adult wasp emerges and flies away.
Parasitic wasps are not deterred by the defences of hosts such as Anelosimus eximius. This is one of the few species of social spiders; they build massive tent-like nests that shelter hundreds or thousands of individuals, who hunt together in raiding packs and even cooperate in raising their young (click the next link to watch their comings and goings). But in the Amazon region, A. eximius can’t evade the Darwin wasp Zatypota sp. A parasitized spider leaves the colony and builds its own cocoon-like web. It then becomes immobilised, so that the wasp larva can unhurriedly consume it. When finished with its meal, the larva enters the cocoon to complete its development. The larger the spider colony, the more chances of being parasitized; up to 2% of individuals become hosts to the parasitoid (Fernandez-Fournier et al., 2018).
Host manipulation seems to be much more common than we thought, so we shouldn’t expect pollinators to be safe from it. And they are not. The conopid fly (family Conopidae) Physocephala tibialis forces bumblebee hosts to bury themselves in the soil just before dying. The nematode worm Sphaerularia bombi, found throughout the northern hemisphere and South America, infects queens of several bumble bee species, castrating its host. And at least for the buff-tailed bumble bee (Bombus terrestris), the nematode also alters the bee’s behaviour (Kadoya & Ishii, 2015). An infected queen feeds normally, but does not breed or build a nest. Instead, she keeps flying into the early summer months, and by doing so she unintentionally helps to spread the nematode. Certainly many other cases of pollinators’ manipulation by parasites wait to be discovered because their effects can be subtle and inconspicuous.
Host manipulation can be seen as a form of extended phenotype (Dawkins, 1982; phenotype refers to a species’ observable characteristics resulting from the expression of its genes). By changing the host’s behaviour for its own benefit, the parasitoid – ultimately, its genes – expresses its phenotype in the world at large. In Dawkins’ own words, ‘an animal’s behaviour tends to maximize the survival of the genes “for” that behaviour, whether or not those genes happen to be in the body of the particular animal performing it’. The phenomenon would have deep consequences for natural selection, but the extent of extended phenotypes has been debated since the publication of Dawkins’ book.
If you are smugly assuming that behavioural puppeteering is for lower animals such as insects, you’d better think again. Some studies suggest that rodents infected with the protozoan Toxoplasma gondii become more active but sluggish in reacting to alarm signals; worse, they may become attracted to the smell of cat’s urine. If so, an infected mouse has a good chance of prematurely ending its days in a moggie’s maw – which was T. gondii‘s ‘intention’ all along, since cats are its ultimate host. And the plot thickens: infected cats excrete T. gondii spores in their faeces, which can make their way into other mammals. A 26-year study with grey wolves (Canis lupus) from Yellowstone National Park, Wyoming, USA, revealed that infected individuals – probably the result of contact with pumas (Puma concolor) – are bolder, more likely to become pack leaders and have better chances of reproducing (Meyer et al., 2022). In humans, toxoplasmosis, the infection caused by T. gondii, is widespread but usually does not have any symptoms. Most people don’t even know they have it, but all sorts of behaviour and mental disorders such as heightened aggression and Parkinson’s disease have been linked to the infection. The effects of T. gondii on rodents and humans have been disputed because data often show weak, inconclusive or no effects (Johnson & Koshy, 2020). In any case, our invulnerability to the manipulative power of parasites should not be taken for granted. Rephrasing the quote misattributed to Margaret Mead, always remember that in biology, Homo sapiens is unique. Just like every other species.
JAC note: I don’t think that in any of these cases of host manipulation (or any others that I’ve heard of) do we know the chemical and developmental basis of the manipulation. What does a fungus do to an ant to make it climb a stalk of grass, grip it tightly with its mandibles, and then die? How does the Darwin wasp manipulate the spider’s behavior to cause it to weave a cocoon-like web instead of its normal web—something good for the wasp? These are incredibly sophisticated manipulations that have evolved in ways we don’t understand.
If this is the work of a creator, he must have been a sadist!
It’s Sunday, and that means a batch of themed bird photos by John Avise. John’s intro and IDs are indented, and you can enlarge them by clicking on them.
“Common” Birds
Several bird species have the word “Common” (upper case C) in their official common name. These are the subject of this week’s post. Oddly, however, not all Common species are particularly common (lower case c), at least in my experience. And, conversely, many bird species that are common do not have Common in their common name. Comprenez vous? The state where each photo was taken is indicated in parentheses.
Today we have a series from Australia by reader Rodney Graetz: bush travel in his country. His captions are indented, and you can click on the photos to enlarge them.
Bush Travel
Bush camping is a pleasant way to travel; isolated, sleeping under the stars in a swag (aka bedroll), and awakening to red earth and blue skies. The mosquito nets are ‘just in case’, but rarely needed. Always hopeful to see, or just a hear, a Dingo, the charismatic native dog. On our way from the cool south to the tropical north of the Australian continent:
There was flooding in the arid centre: The Diamantina River was turbid and full of fish. Our crossing was temporarily halted by a dispute between two egrets (Ardea modesta?). Elegant and effortless flyers, with upraised wings, their ultralight bodies are revealed:
Nearby, a juvenile Nankeen Night Heron (Nycticorax caledonicus), with stylish green legs, was concerned at my presence. Its swollen crop indicates the fishing was good. Interesting, because this species is regarded as nocturnal only, no daylight activity:
Big sky, and long straight road country. All unpaved bush roads develop corrugations, but by adjusting speed, their irritating impact is minimised:
At the end of a long travelling day, a camp in the sandy bed of a large ephemeral creek, and a campfire to sit around, talk, and the watch the stars come out. Bliss!
Dawn (aka Sun sight), in the Outback seems slow compared to the Tropics, as it silently lights up the landscape. The dead trees are all Eucalypts (‘Gum trees’) which germinated and grew after a big flood in 1974 and were subsequently killed by wildfire in the 1990s.
Six White-breasted Woodswallows (Artamus leucorynchus)wait patiently for the return of parent birds. Their graceful flying displays are a pleasure to watch, as is their obedient perching behaviour. Perhaps a parent bird says ‘Sit’, and they compliantly cluster and obey:
At one campsite, a mature adult Little Corella (Cacatua sanguinea) was not pleased that we were close to its roosting tree, producing threating wing displays and much screeching. After the 10-minute display, both parties slept peacefully:
A cluster of ibis in their breeding finery. The rearmost two birds are Australian White Ibis (Threskiornis molucca), and the two foremost are Straw-necked ibis (Threskiornis spinicollis), with one displaying iridescent feathering. The large bird is a Magpie Goose (Anseranas semipalmata): not a true goose, and unusual in that its feet are not fully webbed:
Towards the end of the Dry Season (October), wetlands are drying and crowded. The most common bird here is the Magpie Goose. Experienced Tour guides regularly promise their clients the sight of thousands of Magpie Geese at the large wetlands, such as Mamukala:
Because wetlands are so productive, birds cram them, large and small. Here a foraging, tiny Black-fronted Dotterel (Elseyornis melanops) scampers hurriedly past the towering bulk of a mud-covered, preening Magpie Goose:
A juvenile, Black-necked Stork (Ephippiorhyncus asiaticus), commonly called Jabiru, is the only Australian stork. Beginning life as an all-brown bird, when mature, it is bold black and white, with shimmering neck feathers. A skilled stalker of fish and aquatic snakes, and very people-shy:
Perhaps, the most colourful bird in the Tropics, a Rainbow Bee-eater (Merops ornatus) rests on a termite mound after having captured a large wasp(?). They are common in open woodlands: always conspicuous, always industriously reducing the insect population. By the length of its two tail spines (streamers), this is a male bird:
A feeding cluster of Little Corellas, part of a much larger flock of several hundred young and mature birds. Young Corellas engage in endless play, such as mock fighting and teasing, where one bird will grab a toe of another, then try to tip it over. The two birds on top of this termite mound spent hours preening and repelling other young birds who wanted the high perch. This game was continuously repeated at several other mounds. Birds would fly from one mound to another to contest the highest perch:
No matter how hot you feel, you never wade or swim in the Tropical wetlands. Here a 3+ metre estuarine crocodile (Crocodylus porosus), aka ‘Saltie’, taking a close interest in the boat and passengers. Deaths by crocodile attacks average just two per year, and the details of each suggest the deceased almost always deserved their demise. You cannot fix stupidity:
There are many wise sayings with this same message: The best travelling of all is the journey that takes you back home:
Tony Eales is back, having moved to a new clime. His notes and IDs are indented, and you can enlarge the photos by clicking on them.
It’s been a while. I moved jobs and cities from subtropical Brisbane to temperate Canberra, the Australian capital. Consequently, life has been very busy with fewer opportunities to photograph bugs but I can’t be stopped entirely. My new job looks like it will take me all over Australia so, with luck I will have a lot of different wildlife to show. So far here are some favourites from my new home.
This extraordinary weevil, Acantholophus sp., from the forested hill around Canberra.
A new Arkys for me, Arkys walckenaeri. These are the most common species across southern Australia but become rarer in the subtropics, hence I hadn’t seen one before. Always happy to get a new Arkys for my collection.
This beautiful katydid nymph, probably Caedicia sp. Also from the forests around Canberra.
Southern Australia has a bewildering variety of colourful jewel beetles in the genus Castiarina. This was my first in this new area and a real beauty, Castiarina hilaris.
It’s been wonderful for new beetles down here. This is one of the many pie-dish darkling beetles, Celibe sp.
Neosparassus calligasterBeautiful Badge Huntsman is the star of the show so far. I found it out on this twig at perfect camera height showing off its underside that gives it its name.
. . . and this small horned treehopper that I haven’t quite nailed down the species of yet in the Tribe Terentiini. Charming little bug.
Another southern Australian species that I’ve been trying to find for a while, this pretty little orb-weaver is Araneus ginninderranus.
And this is what I’m most frightened of in this new bio-region: the bullants in the Myrmecia pilosula species complex. These are the only ants recorded to have killed anyone as far as I know. This one is the local Canberra species Myrmecia croslandi.
I found a lot of these mites from the Subfamily Callidosomatinae searching the eucalyptus leaves. This one was taking a special interest in Heteropteran eggs.
Another species I rarely encountered in my previous home but appears to be very common here is Uraba lugensGum Leaf Skeletonizer. You can see them earning their name here.
They are also known as the “mad hatter caterpillar”. As they moult through their instars, the old skin and head doesn’t completley detach from their heads. As they get older, the hat of previous moults gets taller and taller.
Today we have another photo-and-text biology story from Athayde Tonhasca Júnior. Today’s subject is insect sleep and nocturnal behavior. Athayde’s narrative is indented, and you should click on the photos to enlarge them.
When the night has come and the land is dark
We humans spend between 25 to 35% of our lifespan sleeping. It’s a significant chunk of time in the land of Nod, so sleep must be vital. But surprisingly, doctors and scientists are not sure why we sleep so much – or at all, for that matter. A period of unconsciousness may be required so that our body can repair itself and restore some physiological or chemical functions; it could help us conserve energy, especially at night, when our ancestral search for food was less efficient.
Two girls on the stove bench. Art by Albert Anker, 1895. Wikimedia Commons:
Whatever the reason, we need our resting. And so do other animals, including insects. In the case of bees and wasps, females have the obvious option of a cosy nest to tuck into for the night. But males do not: they are not welcome back once they mature and leave the nest, so they are destined for a vagabond life. When the night comes and the temperature drops, they have to rough it by entering a state of torpor until the morning sun heats them up again.
Flowers are the bedding choice for males of many species: on a chilly morning, you may find sluggish bees curled up among petals. These sleeping arrangements offer some protection against roaming predators, are convenient spots for meeting females during daytime, and also make males of some species exceptional pollinators.
But protection doesn’t seem to be crucial, since many bees just sleep in the open. If you visit a garden during early morning or early evening, you may spot bumble bees slumbering on top of a flower, or even hanging upside-down from a blossom or under a leaf. Most of them are males, but the odd female may join them if she’s caught outside when temperature drops quickly at sunset. Watch a sleeping bee clinging to a plant and refusing to be woken up.
Sleeping bumble bees clinging to a Welsh onion (Allium fistulosum) inflorescence:
Some bees and wasps seem to deliberately make themselves uncomfortable for the night. They hang from the end of a twig, a dried flower head or a thin stem, clamped on with their mandibles. We don’t know why they sleep like this; perhaps to make them less visible to predators, who may mistake them for plant extensions.
Male bees are not much into socialising: they tend to avoid each other, when not being downright aggressive. But after sunset, males of some species spend the night close together, forming clusters of bees clinging from branches or flowers. Not only that, these males tend to return again and again to the same spot every evening for their sleep. Gregarious sleeping seems like a dangerous life choice: such concentrations of lethargic bees must tempt many a predator. One possible explanation for this behaviour is the dilution effect: the larger the group of prey, the smaller the chance of any individual being the victim of a raider. Some fish, penguins and mammals that live in the open resort to this type of defence.
We don’t have much information about the consequences of sleeping in the open for male bees. But when you tuck in tonight, remember that a peaceful, uneventful kip is not a given for everybody.
When the night comes to an end in a Central American forest, its nocturnal denizens – bats, owls, rodents and cats – begin to retreat to their shelters. At this time, before the crack of dawn, light levels are up to 100 million times dimmer than during the day, so it’s still too dark for the day-shift inhabitants.
But one creature is already busily going about in the dense tangle of vegetation: the halictid (aka sweat bee) Megalopta genalis is flying from flower to flower collecting pollen and nectar, then navigating safely back to its nest. This is one of the 250 bee species, about 1% of the total bee fauna, known to be nocturnal (active at night) or crepuscular (active during twilight, dusk or dawn). This is a surprisingly large number, considering that bees are essentially adapted for bright sunlight.
Bees, like other insects and crustaceans, have compound eyes, which comprise thousands of independent light receptors known as ommatidia (sing. ommatidium). Images are formed by combining the input from the ommatidia, which are oriented in different directions – up, down, sideways and forwards. As a result of this configuration, image resolution is not very good. When a bumble bee hovers near you, it probably was attracted by the colour of your hat or your scent: it just wants to check whether you are a giant flower. Insects may not see clearly, but many of them have a large angle of view – a feature that makes flies and dragonflies so hard to catch. Some insects also see polarised light, which we can’t.
Drawing of the compound eye of a drone fly from Robert Hooke’sMicrographia, 1664:
In addition to their compound eyes, bees and most other insects have simple eyes (ocelli). These are single lens organs to detect movement and light, and they help the insect navigate during flight. Daytime bees find their way by identifying landmarks around their nests and along foraging routes; directions and distances are also determined visually, with the help of polarised light.
But how doesMegalopta genalis cope with very low light? We know that nocturnal bees can react to faint movements, see polarised light and orientate from landmarks just like diurnal bees, but how they do these things is not completely clear. Night-flying bees have larger compound eyes and ocelli when compared to diurnal bees, but there must be other factors at play such as neurological adaptations; eyes alone don’t explain their visual performance.
The ability to fly at low light evolved independently in bees from the families Andrenidae, Apidae, Colletidae and Halictidae, so there must be selective advantages to being nocturnal or crepuscular. They may be less vulnerable to parasites and predators, or there could be less competition for food. The night fliers may be responding to food availability: many plants bloom only at dawn or at night to save water, while others accumulate nectar through the night, offering rich rewards to early risers.
If you are wondering whether these night-time comings and goings have any consequences for plants, the answer is yes. Nocturnal bees pollinate a range of plants, many of economic importance. Several of these bees are good at buzz pollination, so they may be particularly valuable for plants with poricidal anthers such as Solanum spp. (e.g., aubergines, peppers and tomatoes). But we know little about nocturnal bees: collecting data on pollination ecology is hard enough during day-time, and it becomes a real challenge when the lights are out.
Night-flying bees are representatives of a vast number of nocturnal flower visitors such as moths, whose role as pollinators are becoming increasingly recognised. We need more night owl ecologists to help us understand better their role in our ecosystems.
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:
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 14. Golden-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.
Leopard up a tree:
Male Lion after a kill. This group had just taken down a baby elephant and was methodically eating it. I do have pictures of them eating the carcass but even dispassionate scientific readers might find it a bit disturbing. Happy to share more if you want (also have great video):
Male and Female Ostriches:
African Wild Dog and pack of dogs. Very rare sighting! These are vicious. The only predators that eat their prey alive rather than killing it first:
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