Garter snakes (Thamnophis) are among the most common snakes in North and Central America. Known for their adaptability and varied diets, these non-constricting snakes are popular among beginner hobbyists. Understanding the intricacies of a garter snake's diet is crucial for ensuring its health and longevity in captivity. This article provides a comprehensive overview of what to feed your garter snake, how often, and what to avoid.
Understanding Garter Snake Dietary Needs
Garter snakes are carnivores, meaning their diet consists exclusively of animal matter. In the wild, they are opportunistic feeders, consuming a wide range of prey depending on availability. Their natural diet includes slugs, earthworms, leeches, lizards, amphibians (including frogs and tadpoles), minnows, and rodents. They typically prefer live prey but may also consume freshly killed or recently dead animals, particularly in captivity.
The Importance of Variety
Unless you have a garter snake that readily eats mice, it's essential to provide a varied diet to ensure complete nutrition. A monotonous diet can lead to nutritional deficiencies and health problems.
Ideal Food Items for Garter Snakes
Earthworms
For many garter snakes, worms are often the one food they will reliably eat. Worms collected from your garden (“dew worms”) will be eaten with particular enthusiasm, and nightcrawlers (Lumbricus terrestris) purchased at a bait store will also suffice.
- Pros: Earthworms are readily accepted by most garter snakes, especially younger ones. They can be a reliable food source, particularly for picky eaters.
- Cons: Earthworms are deficient in calcium, and there is some debate about whether this is a cause for concern. If your garter snake's diet is primarily worm-based, supplement it periodically with calcium. Never use red wigglers (Eisenia foetida), which are the worms used in vermicomposting and are sometimes sold as trout bait: they are reportedly toxic to garter snakes. Be careful with nightcrawlers, which are big and muscular: be sure to cut them into small pieces when feeding them to small snakes; they’re strong enough to crawl back out if you’re not careful! Cutting a large nightcrawler into quarters will be enough.
Fish
Many keepers rely on fish because it’s very easy to find, and because it’s easier to control parasites with freezing. Live fish can be advantageous because some garter snakes will refuse to eat anything else. But a regular diet of live feeder fish can expose your snake to several medical problems.
Read also: Understanding Black Garden Ant Nutrition
- Pros: Fish are a convenient and often readily available food source. Freezing can help control parasites.
- Cons: Live fish can carry a load of internal parasites with them that can leave your snake with a persistent infection of roundworms, tapeworms or pinworms that can be difficult to treat. Symptoms of that infection can show up months after the snake ate the contaminated fish. Certain kinds of live fish can pose additional risks. Goldfish should be avoided at all costs; it’s essentially a junk fish with poor nutritive value. And other species of fish contain an enzyme called thiaminase, which destroys vitamin B1 (thiamin) and gives your snake a potentially fatal vitamin deficiency (see Vitamin B1 Deficiency). Not every garter snake will accept fish fillet. Fish fillet is nutritionally deficient without supplementation. Frozen whole fish do not present the same problems with parasites (if frozen for more than 30 days), but freezing does not destroy thiaminase. Alan Francis, a British garter snake keeper, has come up with a recipe for homemade garter snake food based on trout purchased from a nearby trout farm: whole trout are put in the blender, mixed with gelatin, set in blocks and put into the freezer. Strips are broken off as needed. I haven’t tried it yet, but it certainly sounds like a good idea: trout are a safe fish as far as thiaminase is concerned, and freezing takes care of the parasites.
Mice
Although not considered a “natural” diet in the wild, garters will eat rodents in the wild from time to time. In captivity, garters have been fed mice with no apparent ill effects for years.
- Pros: The main advantage of using mice is that they are more nutritious than fish or worms: they do not require supplementation and there is no risk of a thiamin deficiency. Garter snakes feeding on mice don’t need to be fed as often and they grow faster, too.
- Cons: The key thing to remember is never to use live mice. (This alone may make some keepers feel more comfortable with the idea.) Using frozen mice is safer for the snake and more humane for the mouse. Mice come in different sizes: pinkies are newborn mice, followed by fuzzies, hoppers, jumpers and adult mice. A baby garter snake is too small to eat a pinky mouse, but can eat pinky parts or a small pinky after a few months. Adult males and young females may eat hoppers and large adult females may eat adult mice. Thaw the mouse out before offering it to your snake. This can be done at room temperature, or in a plastic bag in warm water. Training garters to eat mice is usually not difficult. Rub a pinky or fuzzy mouse with fish or earthworm to transfer the scent to the mouse. Some garters need no scenting at all and will take mice immediately, and some baby garters will take unscented pinky parts (chopped up pinky mice, cut up when frozen) before they’re big enough to take a whole pinky! Rat pups are another possibility, especially for large female garter snakes. While adult rats are obviously too large to be fed to garter snakes, pinky, fuzzy and even hopper rats can be used.
Foods to Avoid
Frogs and Toads
In the wild, most adult garter snakes feed preferentially on frogs and toads. In a perfect world this would make up the bulk of their diets. Frogs, toads and tadpoles are rife with parasites, and are quite likely to transmit them to your snake. It’s true that wild garter snakes eat frogs and toads all the time, but they’re (a) used to it and (b) rife with parasites themselves. Your pet garter snake won’t necessarily have the same resistance as a wild garter snake whose immune system has been hardened by constant exposure.
Red Wigglers
Never use red wigglers (Eisenia foetida), which are the worms used in vermicomposting and are sometimes sold as trout bait: they are reportedly toxic to garter snakes.
Goldfish
Goldfish should be avoided at all costs; it’s essentially a junk fish with poor nutritive value.
Vegetables
And all snakes are carnivores; they will not deliberately eat any vegetable matter of any kind.
Read also: Weight Loss Claims Examined
Supplementation
Earthworms are deficient in calcium, and fish fillet is not nutritionally complete. I have used a combination of powdered calcium, vitamin B1 (as insurance against vitamin B1 deficiency) and vitamin D3 (to help metabolize the calcium). I’ve received a report that using calcium powder on earthworms will kill them. Lightly dust them instead of dredging them in the powder, and do it just before feeding. When supplementing, don’t overdo it. While vitamin B1 is water-soluble and, as such, theoretically impossible to overdose on, it is possible to get too much calcium and vitamin D3.
Feeding Schedule
How often you feed your snake depends on what you feed it, and how much depends on the size of the snake. Worm eaters need to be fed more often than fish eaters, which in turn need to be fed more often than mouse eaters. Worm eaters should be fed twice weekly, fish eaters can be fed every five to six days or so, and mouse eaters every week. A rigid schedule is not strictly necessary, though it’s easier for the keeper to remember. Snakes that eat a varied diet can be kept on a constant schedule, despite the different recommended intervals I just mentioned. You should feed your snake enough to leave a visible bulge, but not so much that the snake is going to burst. A baby snake should get two or three small earthworms collected from the garden, or one-quarter to one-third of a large bait store nightcrawler, or a few feeder guppies, or one large feeder platy, or one-quarter to one-half of a pinky mouse. Smaller, more frequent meals are more easily digested than mammoth, infrequent meals. It’s hard to make fatal mistakes, and through trial and error you will figure out how much and how often based on how big the snake looks after a meal, and how fast that meal is digested. It is possible to overfeed your snake. Since overfeeding causes obesity and reduces the snake’s lifespan, it should be avoided. Do not feed your snake every day or it will become obese. It’s harder to overfeed on a pure earthworm diet, but easier on a pure mouse diet, because mice are more nutritious than worms.
Feeding Techniques
Most of the time it’s fairly straightforward. Our garter snakes’ cages have paper towels for substrate (rather than wood chips or bark), and they all eat frozen/thawed mice, so all we do is drop the mouse into the cage. If you’re using a different kind of cage bedding, you’ll want to ensure that it doesn’t get stuck to the food. I wouldn’t drop earthworms into a cage full of wood chips, for example, because I’d worry that the wood chips would get stuck to the worm and be swallowed by the snake. Snakes don’t digest plant fibres well at all. Some garter snakes need their prey to move. Garter snakes are very visual, more so than many other snakes, and respond well to motion. This is not a problem with live fish or live worms, but worm pieces (if the snake is very small), fish fillet or frozen/thawed mice may hold no interest for them. In that case you may have to offer the food on tongs, hemostats or tweezers, wiggling it around to simulate motion and stimulate the snake. This is called tease-feeding. (You don’t want to hold the food in your fingers. If you keep two or more snakes in the same cage, you may have to feed them separately in order to prevent food fights and other accidents. In my experience, garter snakes can be some of the most reliable and aggressive feeders of all captive snakes. But there are always a few exceptions. The first and most likely possibility is that you’re offering the snake something it doesn’t want to eat or doesn’t recognize as food. Some garter snakes expect their prey to move; as a result, fish pieces, thawed pinkies, and earthworm pieces cut too small for them to twitch may be ignored. You may have to experiment: try larger pieces of worms (big enough to still be twitching) or smaller, whole worms; wiggle the food in front of the snake with a pair of tweezers; offer something else. You might also be offering it the wrong food. Remember that some species don’t eat certain things - ribbon snakes don’t eat worms, for example. Sometimes garter snakes lose their appetite when winter comes. It may be a sign that you should hibernate (or, to be more technically correct, brumate) your snake. But sometimes I’ve found that garter snakes don’t go off their feed altogether, they just get finickier. For example, I’ve had a few snakes that had been converted to mice suddenly refuse to eat them when October rolled around, but they did eat when they were offered worms or fish. After a while they began taking mice again. So try feeding your snake something else. Another possibility is that you have a male garter snake and it’s mating season. When he was introduced to his mate, my male Red-sided Garter Snake refused to eat for two months; I might have gotten a few worms into him during that time, at best. Finally, the snake might be too nervous to eat - especially with you watching it. There are some things you might want to try. If the snake has just arrived, give it at least three days before offering it any food - give it time to adjust to its new cage. Leave the snake alone while feeding: it might be too terrified of you to pay attention to the fact that there’s a tasty morsel in front of its nose. The worst-case scenario is when a snake needs its food to move but cannot eat in front of you - in other words, you can’t tease-feed it.
Read also: Diet of Argiope aurantia