Snakes are pretty weird guys – their mouths can disarticulate to accommodate some strange prey, they can have “virgin births”, they’re pretty great actors, and sometimes they’re born with multiple heads. But their quirks don’t stop there: they also have one of the most unique digestive functions in the animal world. Yes, we’re talking shit.

Despite mostly looking pretty similar, there are actually 15 known snake families with 2,400 recorded species, each with their own unique physiology, preferred prey, and hunting styles. Being able to stretch their mouths up to five times larger than their own heads means snakes are capable of putting away pretty much anything – an ability that has awarded some snakes, like blood pythons (Python brongersmai) and corn snakes (Pantherophis guttatus), the colloquial name of “garbage disposal” species for their willingness to eat anything and everything.

The choice of prey and hunting styles of different species, unsurprisingly, has a huge effect on their toileting habits.

Ambush vs. active hunters

Among both venomous and non-venomous species of snakes, there are ambush hunters and active hunters. Ambush hunters are generally terrestrial species, meaning they’re more heavy-bodied and live predominantly on the ground in burrows. Active hunters are commonly arboreal or semi-arboreal, meaning they live off the ground or have the ability to climb trees. Active hunters are usually smaller and more agile with skinnier bodies.

Prey choice, frequency of eating, and defecation habits are all closely related to whether a species is an active hunter or an ambush hunter.

Active hunters like the semi-arboreal, non-venomous rat snake species feed frequently on small rodents, fish, and large insects. These comparatively small snakes have more consistent prey items and frequent meals, and so defecate frequently too, roughly 2-7 days after eating.

These active hunter species expel more energy through moving, are more negatively impacted by carrying extra fecal weight, and come into more regular contact with food, meaning their metabolic process is faster leaving the revolving cloacal door constantly turning.

Ambush hunters, on the other hand, catch their food by lying in wait, usually in their burrows, or venturing out slowly but remaining firmly on the ground. These species expend such little energy in their daily life that they don’t need to eat very frequently. They also come across food far less often, meaning they eat a more inconsistent and varied diet that can involve both large and small prey.

Defecating could even be detrimental to these ambush hunters. Shedding a few extra pounds of their big fat weight doesn’t benefit them in the same way it does for active hunters, and the smell might even attract predators into their burrows or scare prey away.

Sumatran short-tailed pythons (Python curtus) and blood pythons (Python brongersmai) are incredibly heavy-bodied, terrestrial species that are slow on the ground. They eat roughly every 10 to 14 days and drink more water than other species, but will hold onto their waste and release it between once every couple of months to once a year – and as you can imagine, when they go, they go.

This impressive ability to retain waste means that up to 5-10 percent of a snake’s body weight is taken up by feces – so a 90-kilogram (198.4-pound) snake could be holding onto a whopping 9 kilograms (19.8 pounds) of poop at any one time. This additional weight is so significant that when monitoring and recording the weight of captive individuals, keepers measure their “empty weight” – that’s pre-feeding and post-defecation – to get a true idea of body condition.

While the exact reason snakes have evolved to hold it in for so long is still unclear, one of the theories of the potential benefits is to act as a ballast during strikes. As the waste is carried so low down on the snake’s body, when they lurch forward to strike it’s thought this additional weight might be holding the body in place, allowing for more control when taking down larger prey.

Snake anatomy

Snakes’ unique pooping habits come as a result of their weird and wonderful digestive tracts. Without any defining shape to their bodies, it’s difficult to know where their necks end and their tails begin, and when you take a look inside, it doesn’t become any clearer.

For example, snakes breathe predominantly out of their right lung. While their left lung is comparatively tiny, vestigial, or sometimes absent, their right lung stretches down roughly half of their body. Their esophagus, which one would expect to delineate the animal’s “neck”, also stretches down the same length as the right lung, leaving just a small area above the cloaca designated for the intestines and other organs.

This elongated esophagus is what enables snakes to swallow prey whole as the structure’s hard ridges help to compress food and pass it slowly down towards the stomach. This means it takes snakes between 24 hours and a week to digest an appropriately sized meal, and the length of this process is dependent both on the size of the prey and the environmental temperature.

Like humans, snakes have a monogastric digestive system – meaning their stomachs have just one chamber – but that’s about where our similarities end. Snakes have a J-shaped stomach that starts around the middle of their body where the majority of the digestion takes place before moving to the intestine for nutrient extraction. During digestion, snakes’ intestines double or triple in weight, increasing their digestive enzyme output by up to 60 times.

Snakes do not have a butthole; instead, after digestion food moves to the cloaca chamber. With one hole to rule them all, the cloaca is a structure that facilitates the release of waste and is used in mating. Cloacae, which is Latin for “sewer”, are found in reptiles, amphibians, birds, elasmobranch fishes (like sharks), and monotremes.

The cloaca plays an important role in the reabsorption of water after the digestive process has taken place. As some snake species get the majority of their water from their food, their waste is often very dry and hard. Exiting alongside the fecal waste is the snake equivalent of urine, called urates. Urates are pale, dry, chalky lumps that are made up of ammonium acid urate and uric acid dihydrate with very little residual water content.

However, not all urates are created equal. A 2021 study looked at the differences between the urates of modern snake species (Colubridae) and ancient species (boas and pythons) and found that they had different chemical and structural differences.

These observed differences suggest snake species have more than one way of processing waste, and while the reason for this remains unclear, the researchers speculate that these urates may be a form of social communication.

Despite being some of the strangest (and coolest) animals on the planet, very little is known definitively about snake physiology, evolution, and behavior – but as snakes become more prevalent as pets, invasive species, or even as a source of food, we will hopefully learn more about their weird and wonderful world.