New Garter owner!

[MichaelSmith]

The 'natural diet' discussion comes up from time to time, and it does not seem that anyone has done the work to give a definitive answer. Should garters only be fed what that subspecies eats in the wild? The garter I work with most is the eastern blackneck, which I'd put money does not eat mice in the wild. Yet, it's not so hard to switch them to mice using frog-scenting. Am I depriving them of essential nutrients or loading them up with too much of other nutrients? The only answer I can offer is that mine eat a rodent diet and seem quite healthy. And ... lots of people keep garters on a completely mouse diet with good results. I think even those species that take some mice in the wild do so opportunistically, so that a 100% mouse diet is probably "unnatural." That does not necessarily mean it is unhealthy.

I'd offer this speculation: could it be that in the course of speciation, many members of the genus Thamnophis may have evolved certain behavioral prey preferences, but perhaps their digestive systems have not changed in such a way that they (most, anyway) cannot thrive on a mouse diet. That would seem to be in line with the experiences of garter keepers that feed mice. Not that I 'know' this to be the case, but it seems like an interesting guess.

It would be nice if someone were able to do some controlled experimentation with one group being fed mice, and the other matched group being fed a diet based on whatever is known of their wild diet (from habitat, observation, stomach contents studies). Growth, mortality, reproduction, and other measures could be recorded and compared, to see what differences there may be.

[ConcinusMan]

Honestly that's a very level headed logic you have. You have to also understand that in the case of a snake such as T. s. concinnus is that even though it's only subspecies of Thamnophis sirtalis, (which with it sometimes breeds) it's really restricted in it's habitat needs. It is never found far from water, prefers wetlands near lakes streams, etc.,(loaded with small frogs) has a very limited range and seems this is a result of specializing and naturally, what's on the menu in wetlands? you don't have to guess.

However, just plain old T. sirtalis doesn't seem to very common around my area, but I have found a few over the years and like concinnus, they're on average much larger than any of our other 2 species, but I usually find them fairly far from water unlike concinnus. Seems to me that these individuals are likely to readily eat a few baby mice if they encounter a nest since there's not much frogs or fish around where I find them. So, if you look at the range of the eastern blackneck, (in spite of it's wet habitat and food preferences) is prone to drought so it's not such a stretch to imagine that they will eat mice too, if they encounter a vulnerable nest and their main food has become scarce.

You said "could it be that in the course of speciation, many members of the genus Thamnophis may have evolved certain behavioral prey preferences, but perhaps their digestive systems have not changed in such a way that they (most, anyway) cannot thrive on a mouse diet"

I would say that is very likely. I'm sure any Garter species could be maintained in perfect health on a rodent diet. Even if you had to chop it in little pieces for small ones, if they'll eat it and digest it, then there's no problem health wise. I'd say with a garter in captivity, even if it's far from the wild removed C.B. concinnus, it's a good idea to offer them a variety of foods including fish, tadpoles, frogs, worms, etc. if you have a source for that, and see what they prefer, instead of raising them exclusively on rodents from birth.

You are right though. Even if it's unnatural for concinnus (for example) to eat rodents, it doesn't mean it's unhealthy. If a c.b. loves them and is healthy, but after offering a variety of it's natural foods, feed it what it seems to prefer.