This (partly modified) article has previously been published in:
Litteratura Serpentium (European Snake Society) and
The Garter Snake (European Garter Snake Association)
Introduction…
When you tell someone you keep garter snakes in the terrarium as a hobby, you usually get one of the following three types of reactions:
- Yuck, that’s scary, is that dangerous, etc. (the majority).
- Gosh, how nice (and people want to know all about it).
- Oh, that’s easy. Just feed some fish and you are ready (often this is said by people who keep rodent-eating snakes and therefore think they know everything about the feeding of garter snakes).
At question 1 you try to explain that it isn’t all that bad (999 out of 1000 times without satisfying results, but you keep trying).
At question 2 you tell all kinds of things about your hobby till you notice that the attention is weakening.
But at question 3 I usually give the answer that feeding rodents is easy and that it’s not that easy to compose the right menu that is as varied as possible for garter snakes. This reaction often surprises them.
I regard garter snakes as opportunistic hunters. There is a wide range of preys within their range so they will usually eat what is available at that time. What actually is eaten depends on the habitat where the snakes live, the presence of prey there and the place which a snake occupies in the habitat (waterfront or more land inwards).
This opportunism also includes the “eat till you burst-phenomenon” when there is a lot of food available in some periods. But also include the fasting periods which undoubtedly occur every now and then, for example during extended drought and/or heat-periods. Such “rich” and “poor” periods normally occur each year and is for the garter snakes quite normal and usually harmless. I heard from people who have observed garter snakes in the wild that, in the same area, they found in one period many well-fed snakes and found in other periods many skinny ones. The reserves which are stored by the snakes during the “rich” periods help them through the “poor” periods.
Within the group of Thamnophis keepers there are different opinions about what is good or isn’t good for their snakes. For example, you see that many Thamnophis keepers in the USA and Germany only feed rodents to their snakes, where in Europe there are much more people that feed them mainly with fish and fewer with mice. Who knows best cannot be established. And in my opinion that is not important.
Major breeders in the U.S. feed mainly rodents and have good breeding results.
The Dutch breeders Gijs & Sabine Komen feed rodents as well as fish and have good breeding results.
And other Dutch breeders like Steven Bol, Sjoerd van Veen and I myself also breed many young of many species and feed their snakes mainly with fish.
About the age that the snakes reach in both “groups” are no accurate data available. But I do know that many snakes of the above mentioned “fish-feeding and fish/rodents breeders” become as old as you’d normally should expect. Ages up to 10 years are no exceptions.
For me, variety in the menu is the most important and a continuous abundance should be avoided.
I am convinced that if you vary as much as possible in terms of nutrition, the snakes have the best chance to get all the nutrients.
Next to that there is another advantage. When you feed only one type of prey and this prey is, for any reason, unavailable for a period, you might have a problem. When you feed a wide variety of preys (or parts of them), there is always something available in periods of shortage.
The intention of this article is not to discuss who uses the best method. I just want to discuss my way of feeding and tell something about “why” I’m doing this, “how” I do this and “what” I feed my garter snakes.
I will also, where available, show some nutritional values of various types of food. The specified nutritional values may of course vary because these foods are natural products. They are meant as guidance.
I also have to be honest: the absolute necessity of a large variation in food supply is also comparative. In the eighties I bred large amounts of Nerodia fasciata on a menu that consisted of at least 80% chicken-stomach and chicken-heart and for the other part consisted of fish fillet. In this period suitable small fish were poorly available in the area where I lived.
This food was always supplemented with some extra calcium and minerals/vitamins (mainly Gistocal). Vitamin/mineral supplements, especially made for reptiles, were in that period not yet available. The snakes, adults and babies, did great on this menu.
Why?
To start: why do I feed in this way?
Firstly, I think feeding only feeding rodents is “too easy” and to me that’s like “getting something for free”. It looks beautiful but at some point you have the feeling that you end up getting screwed.
Next to that I also want to satisfy the opportunism of the garter snakes as much as possible… therefore offer variety. Personally I think feeding garter snakes with only rodents is to unilateral. And continuously feeding such energy-rich preys does not fit in my view of the above discussed opportunistic lifestyle of Thamnophis.
The search for other food items – to make the menu even more varied – is an essential part of the Thamnophis hobby for me.
In the diet of garter snakes in the wild, rodents are only available in small numbers (except for Thamnophis elegans and perhaps a few other species that are not necessarily living in the immediate vicinity of water for a large part of the year, such as Thamnophis scalaris).
In the article by Edgehouse, Michael J. (2008) are, amongst other info, some interesting tables (table 1 & 2) containing research results of what Thamnophis in the wild eats.
Of course it all depends on the location where individual snakes are found. When a population lives, for example, near a water where barely live fish, but is teeming with frogs, it is logical that more frogs than fish are found in the stomachs.
What is most striking is that the most important part of the diet consists of frogs and fish. And that mammals only play a role in T. elegans.
Frogs as the main prey therefore probably should have a high priority in the terrarium but it is not that easy to get large amounts of frogs. In the Netherlands all amphibians and reptiles are protected by law (and that is a good thing), so these shall not be eligible. One could start breeding frogs, but this would have to be a very large one when you want to have enough frogs of all kinds of sizes during 8 to 10 months per year.
But the most important reason for me to feed no frogs is a sentimental reason… I love frogs and I would not be able and/or willing to kill them and use them as food for my snakes.
And since there are sufficient alternatives that are easily obtainable throughout the year and where my sentiment does not matter, I’ll do it without frogs.
In short, the food that I give has to comply to:
- It has to be nutritious.
- It has to be easily obtainable in a large part of the year, fresh or frozen.
- It has to be affordable.
How?
If there are multiple snakes in one terrarium I cut the food into bite-sized pieces that are about the same size as the heads of snakes. This to make it more difficult for the snakes to steal the food from each other and in this way prevent that they devour each other. Anyway, you should always stay with your snakes when they are eating. So you are able, when things go wrong, (to take a picture and) take the animals out of the terrarium and force them to let go.
Normally the snakes that live in the same terrarium are about the same size.
I cut the food with scissors because this works the best for me. I am experimenting with a blender, as this could save a lot of time, especially if you have to feed a lot juvenile snakes. Put the first attempts were not very satisfactory. But this will be continued.
When there is only one snake living in the terrarium it gets whole smelts and pieces of other food that has the right size for him/her. It is not necessary to stay and observe these snakes that are alone.
On the bottom of the feeding bowls I sprinkle a thin layer of a generally available multivitamin/mineral powder which is specifically formulated for reptiles. This is supplemented with extra vitamin B1 (Thiamine) and Calcium. Since a few years I restarted to add this every second (or sometimes) third feeding. The supplements are thrown away every year during the brumation and bought fresh in spring.
In newborn snakes that have never eaten before I leave all the additions omitted. When they have eaten 3 or 4 times I start to add small amounts of supplement. I noticed that when you add supplements at the very first feeding they’re less easy starting to eat. Once they have eaten 3 or 4 times the supplement does not bother them any more.
The first food that I offer are small pieces of smelt. When this does not work after two attempts (two or three days have passed) , I turn to salmon or pollock fillet. Normally one of these three types of food are attractive enough for them to start eating.
The first two/three weeks I place a small bowl with food in the terrariums of the juveniles almost every day. In these bowls I put some water in which the fish has thawed. I noticed that the little snakes start to eat faster this way, but also better. When the first two/three weeks have passed, it is pretty good visible which snakes eat well and which are not. The size difference is already well established.
I now catch the non- and/or poor eaters from the terrarium and put them in a separate enclosure. The young snakes that are eating well now get food every second day and I keep doing this for about a month.
The non- and/or poor eaters have more rest now because they are separated from the brutal ones. Most of them start eating now without much extra attention. Sometimes it is necessary to try some other fish such as cod, dab and sprat. Once I triggered some stubborn, non-eating Thamnophis fulvus juveniles to start eating on small pieces of see needle (Belone belone). Once they had eaten 1 time they accepted other fish too. You sometimes have to experiment a bit.
These stragglers get during the following four weeks, food on also almost every day. After about 4 weeks they get food every second day. The few snakes that continue to refuse everything and start to look poor I kill in order to prevent an agony.
When all the young are about two months old the feeding is reduced to every 3 to 4 days. Most of the “laggards” are now about the size of the snakes that ate well from the start. These are then reunited with their siblings. The few specimen that still are smaller than the rest get the name “misfits” and get extra attention from now on and stay separated from the others. But only when they are doing fine but do not grow as fast as their siblings. This means that they are getting even more variation and also are more often fed. Generally, these ”misfits” have reached the length that you would expect to be normal after a year or so. These “misfits” are not sold in their first year, are brumated and when they do well in their second year they are sold (or I keep them myself).
All the young from species that need a brumation are brumated in their birth year and this never caused any problems.
After their first brumation the young get the same feeding rhythm as the adults. This means that they are fed every 5 – 8 days. When they only get fish they get as much food as they can eat. When I add meat, they get less.
Nowadays I don’t feed all snakes simultaneously to save me some time. I start a feeding sessions two times per feeding period. I try to feed the snakes that live alone (and therefore don’t need supervision) on one day and the others a few days later. And then it sometimes happens that, when after a few hours not all the food is eaten, I place the bowls with leftovers in other terrariums. But when it is their regular turn to eat, they again get food. This creates quite a lot of irregularity and that is exactly what I want.
What?
Smelt…
To start, these small fish have the ideal size to feed to fish-eating snakes. Furthermore they are relatively easy obtainable, both fresh and frozen, they are affordable and seemingly the garter snakes find them delicious. Another advantage is that their fish bones are quite soft so there is no danger the snakes get injured when they eat smelt that is cut in small pieces. They are whole fish with all the organs and bones still in it. So they have a good nutritional value.
There are two different species that I feed, the big-scale sand smelt (Atherina boyeri) and the European smelt (Osmerus eperlanus). This depends on what my dealer delivers.
On the internet I found some information about the nutritional value of smelt.
85 grams smelt contains 105 calories, 19 grams protein, 2.6 grams fat, 76 mg cholesterol, 0,699 grams of monounsaturated fatty acids, 0,965 grams polyunsaturated fatty acids and is rich in minerals and vitamins.
The only disadvantage is that smelt contains thiaminase, but that is easily solved by adding thiamine (vitamin B1) to the fish. Thiaminases are enzymes which split/break off the thiamine molecules and make them inactive. In all the years that I feed smelt to my garter snakes I have never had one specimen that suffered from the symptoms that can occur by thiaminase. For more info about Thiaminase I refer to www.thamnophis.eu.
I think smelt forms some 75% of the menu of my garter snakes.
Rodents…
I seldom feed mice to my garter snakes and when I do it is most of the times to pregnant females. They never get more than 2 to 4 pinkies during their whole pregnancy.
All the other garter snakes are rarely, if ever, fed with mice or other rodents.
Day-old-chicks…
For a year or two now I feed day-old chicks to my garter snakes every now and then. Initially only the large females (T. eques scotti and T. sirtalis tetrataenia) were fed every now and then with day-old chicks. The first-mentioned gets every 4 – 5 weeks a whole day-old chick and the female San Francisco garter snake than gets one that is cut in pieces. A whole chick is to big for her.
But when I noticed that these chicks were eaten very fanatically by those two females I started to feed them to my other garter snakes too every 4 – 5 weeks. I cut the chicks into pieces of the appropriate size and add them to a bowl with pieces of smelt. It’s nice to see that most snakes flawlessly pick the pieces of the day-old chicks from between the fish. I feed the meat the bones and the organs from the chicks; many pieces also have some fuzz feathers attached on it. Only the heads of the chicks are not cut into pieces; they are fed to the two big females.
Also the baby snakes are fed with these chick pieces every now and then. They love it.
The great advantage of day-old chicks is that they are widely available (frozen), not expensive and have an excellent nutritional value.
Possible drawback is that it is a dirty job to cut the chicks into pieces, but I personally do not mind to do it.
The problem I have often heard in the past, for example in snakes of the genus Pantherophis, that their feces are very thin and terribly smelling after eating day-old chicks. I have not observed this in my garter snakes. Feces of Thamnophis has no solid consistency anyway and the smell is not strikingly different from when they only ate fish.
On the website of Rodentpro I found some data about the nutritional values of mice, rats and day-old-chicks.
Personally I have never fed rats to my garter snakes.
On the website of Academia.edu you can find a PDF-file in which is explained that day-old-chicks are suitable food for snakes in captivity.
Sprat…
On the order list of my smelt-supplier I saw that he had frozen sprat (Sprattus sprattus). They are sold as whole fishes, with head and organs. The sprat belongs to the herring family (Clupeidae), so it is plausible that it contains thiaminase.
By the way, I always consider fish of which I have no information, is containing thiaminase.
These fish are about 10-12 cm long; the “meat” is somewhat dry and stiff.
My big females get whole sprats and the other snakes get pieces of it. Most snakes in their first year are not fond of this fish and therefore don’t get it anymore. It is a difficult fish to cut in very small pieces, so this also is a good reason to stop feeding it to the young ones. Most of the older snakes don’t mind eating it. I give it about once every 6 weeks. The high sodium value of sprat doesn’t worry me since I do not feed it often.
Fish fillet…
Once in 2 – 4 weeks I give my garter snakes fish fillets. This is usually combined with smelt or something else, but sometimes I offer it to the snakes without something else. But I always add the multivitamin/mineral supplement that I mentioned earlier.
The most used fish fillets are salmon, pollock and cod. But sometimes I also give them pieces of flounder, dab, trout, etc. when we eat this ourselves
It can be important whether the fish is bred in captivity or caught in the wild. I prefer wild caught fish because there are all kinds of negative stories about captive bred fish, such as about the use of antibiotics, lower nutritional values, etc.
Look at this webpage for some info. Because I cannot check if this also is the case for captive bred fish in the Netherlands I do not give it to my snakes. Better safe than sorry.
Some garter snake species prefer salmon; others prefer pollock. This is a matter of trying out. Also individually, there sometimes is a difference in preference. For this reason I combine some fish species most of the time.
Fish waste…
I am always searching for ways to expand the menu. At one point I had an idea that in the meanwhile has been tested successfully.
One of my brothers loves to fish. Most of the time this is done in the Ooster- and Westerschelde and other waters in Zeeland.
I asked him to freeze the fish waste that remains after the emboweling of the fish. I was particularly interested in the organs and the gastrointestinal system. There are many nutrients in it. To avoid the (small) risk of parasitic infections, the “waste” remains frozen for at least a month.
After I thawed a portion I needed to cut it in the right sizes. There was also a head of an eel and that had the right size for my T. eques scotti female. The stuff is quite slippery and therefore difficult to grab from the tray for the snakes. Therefore I handed the pieces with long tweezers (in this way I also could control the eating). Even the erythristic common garter snake female accepted the feeding with tweezers. Normally she does not accept any food that is “hand-given”.
Feeding this stuff is quite a filthy business and for that reason I later only feed it in Curver-boxes. The first time I offered it in the large fire-place-terrarium so I could make some nice, tasteful pictures.
I also fed it to my newborn snakes and they love it too.
Normally I combine it with smelt or fish fillets.
I offer this food once every 1 to 2 months, depending on the fishing achievements of my brother Ed.
I think it is an ideal food to combine with fish fillets. Just add some calcium and you have a whole fish.
Mackerel…
In our local supermarket I found, next to frozen salmon fillet, some frozen mackerel fillet for a reasonable price. Because I never fed mackerel before at my Thamnophis, I thought: let’s give it a try. This fish is caught at the Norwegian coast and has the MSC certification. This means that it is certified sustainable seafood.
I already fed salmon to all my garter snakes every now and then because they like it very much and because of the Omega-3 fatty acids it contains.
100 grams of salmon contains 3,4 grams Omega 3 fatty acids.
Why try mackerel?
100 grams of mackerel contains 6,6 grams Omega 3 fatty acids.
Mackerel (Scomber scombrus) is a fatty fish that is high in two kinds of omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Omega-3 fatty acids benefit the heart and blood vessels. So when it’s healthy for humans it probably is also healthy for garter snakes.
Next to the omega-3-fatty acids, mackerel also contains other vitamins and minerals (see the “nutritional values” page).
These amounts may vary, of course, because it is a natural product.
All the species that I offered it to, there were at least one or two specimen that ate it. Some of them ate a few pieces, others consumed all the fish pieces. There were also individuals who did not eat from it. Whether they did not like it, had no appetite at that moment or started their shedding process, I cannot tell. On the other hand, the specimen that ate it, ate eagerly.
I have no plans to give my garter snakes mackerel every week. I will only feed it every now and then. Probably in combination with the intestines and organs of other fish.
Research shows that omega-3 fatty acids reduce inflammation and may help lower risk of chronic diseases such as heart disease, cancer, and arthritis. Omega-3 fatty acids are highly concentrated in the brain and appear to be important for cognitive (brain memory and performance) and behavioural function.
Top 5 of fish that contain Omega-3 fatty acids is:
Salmon, (fresh) Sardines, Smelt, Shad (Alosa sapidissima – a Herring species) and Anchovies. More info…
On the blog Jen Reviews you can find detailed information on all kinds of health aspects of nutrition.
Here you will find the extensive article about omega-3 fatty acids.
Definitely worth checking out if you want to know more about it.
Dillies…
Dillies are small, benthic inhabiting deep-sea fish that can be bought as a frozen product in 100 gram packs. I have no i
dea if they are available everywhere, but my smelt supplier sells them in any case though.
These fish are 1 to 4 cm long and this format seemed ideal to feed to my baby snakes.
However, not all the little snakes like them. But when I add some of these fish to the bowl with smelt etc. they do eat them anyway. I have no idea what their nutritional value is, but since it are whole fish with everything still in it I suppose they are an addition to the menu. I do not feed them often, maybe once in 6 weeks.
Chicken organs…
Fresh chicken hearts, chicken stomachs and chicken livers are, in the Netherlands, sold in lots of supermarkets. You
can buy them the whole year and they are not expensive. This organ meat is sold as cat food, but chicken livers are also great for people if you bake them. I usually buy a reasonable amount at the same time and freeze it in portions.
I feed these chicken organs once per four weeks to my snakes. Usually I combine them with pieces of smelt, etc.
Also with this food there are many snakes who first pick the pieces of meat out of the bowl before they grab the fish pieces.
When feeding this meat you have to be extra alert when two snakes decide to grab the same piece. These pieces of meat do not break in two as easy like the pieces of fish. The chance that one snake swallows another one is imaginable.
Not all snakes are keen about the liver, but when it is combined with fish most of them will eat it.
Earth worms…
In the past I have tried these but not in the last years. At first I do not like to dig. And I do not trust the earth worms that are sold as bate for fishing purposes. These are not meant for consumption and you never know what may have happened with them. Earthworms are often used to get the young snakes started. But in my case fish generally works fine too, so I simply banned earth worms.
However, I again have fed earthworms in 2014. The offspring from Thamnophis sirtalis pickeringii (2014) had starting problems when I gave them fish. Combined with earthworms they immediately ate well.
When I had a reasonable amount of earthworms, I froze them. This worked just as well as fresh earthworms.
Clear data on the nutritional value of earthworms I did not find. I do not think I harm my snakes by not giving them earth worms.
