Thread by @HeatherEHeying

Garter snakes fail social distancing. News at 11.

(A snake thread in 18 parts)
sciencemag.org/news/2020/05/g…

Snakes are more social than we think. These snakes aren’t merely aggregating—clustering together for warmth or protection against predators—but actually returning to be with the same individuals, time and again. 2/
…nk-springer-com.ezproxy.princeton.edu/content/pdf/10…

So given that snakes like to hang out with the same snakes all the time—they’re expert at “sheltering in place”—how do you figure out what their preferences are?

You “shuffle” the snakes, and watch them return to their preferred social groups.

Snake shuffling for the win. 3/

Snakes go out together:

“We also found that our snakes coordinated the times they spent exploring outside the shelters, especially in the middle of the day, such that they were more likely to be outside the shelters at the same time than would have been expected by chance.” 4/

Some differences between humans and snakes (an incomplete list, to include mention of legs, hair, and tongues; chromosomes, hunting style, and suitability as campfire companions): 5/

Snakes are modified lizards. Leglessness in lizards has evolved several times; in only 1 of those instances do we call the resulting organisms “snakes.”

Humans, in contrast, are not modified lizards. Go back far enough, and we have a reptilian ancestor, but not a lizard one. 6/

Snakes have indeterminate growth, meaning that they continue to grow in size as adults, albeit ever more slowly. (This is also true of crocodiles, which are not lizards.)

Human (and all mammal) skeletons, in contrast, show determinate growth, which stop growing at adulthood. 7/

Snakes have scales, and no hair. Humans have hair, but hair—like fingernails, and like the feathers of birds—is evolutionarily modified scales. So in a sense, in the same sense that we are heavily-modified reptiles (but not lizards), we also have heavily-modified scales. 8/

Snakes have no eyelids. A clear scale covers each of their eyes, and when they shed their skin, the eye-covering-scale is also shed.

In humans, our “third eyelid” (the nictitating membrane) has become vestigial, and retreated to the medial corner of our eyes. 9/

When snakes flick their tongues, they capture odorants on their tongues, then place them on the vomeronasal organ for chemical assessment.

Forked tongues are used to triangulate the location of airborne odorants.

When snakes shed, the tips of their tongues often shed, too. 10/

Whereas all humans are viviparous (having live birth), some snakes are viviparous, some are oviparous (egg-laying), and some are ovoviviparous (having eggs which hatch inside their bodies just before birth). 11/

Most snakes, like all mammals and birds, have sex chromosomes, meaning that their sex is “determined” by their chromosomes. In some snakes, though (as in turtles, ‘gators), sex may be determined by the temperature they experienced during a critical period in development. 12/

Male humans have one penis, but male snakes have two (technically, “hemipenes”). No, they cannot use both at the same time. Yes, they seem to alternate which side they use. That is all. 13/

Snakes are ectothermic, gathering heat from their environment (which can mean other snakes, and often includes sun-baked rocks, soil, and asphalt). Humans, like all mammals (and all birds, via convergent evolution) are endothermic. 14/

Snakes have extremely kinetic skulls, due to the loss of several skull bones, and their jaws are only loosely connected to their skulls by a ligament. This allows them to do crazy things like eat things larger than their own heads. 15/

Almost all snakes lack legs, have only one functioning lung, and have venom glands.

Boas and their relatives are the exceptions to all of these. (Boids and other basal snakes have primordial pelvic girdles and femurs, tiny little leg bones with no apparent functionality.) 16/

Snakes are dedicated carnivores, and they hunt alone. Unlike in humans, where obtaining food (be it hunting, gathering, agriculture, or dining out) is often a social exercise, there is no cooperative hunting in snakes. They’re not hanging out. Snakes don’t have potlucks. 17/

Snakes lack the expanded cerebral cortex of humans (ever bigger and more complex in mammals --> primates --> apes --> humans), which allows for rumination, scenario-building, and story-telling.

For this reason, and this reason alone, snakes make poor campfire companions. /end