Solely fish-eaters?

[Bart]

I wonder if there are Thamnophis species that lives solely or mainly on fish? I always thought garters eat mainly amphibians and fish only time to time...

If so, how do they deal with thiaminase? Or maybe they are immune to it or their prey lacks it?

[guidofatherof5]

I'm not sure if there is a species that feeds solely on fish. They are all opportunistic.
Not all fish carry thiaminase.

[Bart]

Yeah, I know there are fish that don't contain thiaminase. Afterall I was feeding my snakes with guppies, right? But most fish do, especially relatives of goldfish and I suppose those fish, just like in Europe, are most common in lakes and rivers.

Anyway, there are specialised Thamnophis like ribbons that hunt only fish and amphibians. And I was curious if there are dedicated fish eaters.

[thamneil]

I believe some of the Mexican species are fish specialists. I'm sure someone with more experience will chime in.

[d_virginiana]

Well, any relative of the goldfish in America is invasive. Unless you're in an area that is highly ecologically disturbed and the native species populations damaged, you shouldn't see many goldfish or carp swimming around (there are plenty of places where you do, but garters evolved without them there). I would say that trout and trout relatives are probably most common in rivers in my area, and in slower-moving water crappie and bluegill are very common. I believe those are all thiaminase-free species?
Most species that are fish specialists in the wild can still be taught to eat pinkies in captivity though, like ribbon snakes.

Thiaminase poisoning is typically a long-term process (though I imagine some snakes may be more sensitive than others). If the snake were eating a balanced diet and not JUST one species of thiaminase-containing fish, I would imagine it could get well into its reproductive years before noticing any effects, maybe even live a natural lifespan and die of predation or disease. Of course, in the wild this would probably happen in the first five years or so, which is pretty short compared to a captive garter. That being the reason keepers can be so paranoid about the thiaminase issue, since we want them to live as long as possible

[chris-uk]

I've not gone back to retread Connant's paper on Mexican species, but I seem to remember that the species he described that were feeding mainly on fish were also eating other prey. The Lake Cuitzeo Garters feed mainly on the small fish in the lake, but I think it would be a leap to describe them as solely fish eaters.

[Bart]

Well, any relative of the goldfish in America is invasive. Unless you're in an area that is highly ecologically disturbed and the native species populations damaged, you shouldn't see many goldfish or carp swimming around (there are plenty of places where you do, but garters evolved without them there). I would say that trout and trout relatives are probably most common in rivers in my area, and in slower-moving water crappie and bluegill are very common. I believe those are all thiaminase-free species?
Most species that are fish specialists in the wild can still be taught to eat pinkies in captivity though, like ribbon snakes.

Thiaminase poisoning is typically a long-term process (though I imagine some snakes may be more sensitive than others). If the snake were eating a balanced diet and not JUST one species of thiaminase-containing fish, I would imagine it could get well into its reproductive years before noticing any effects, maybe even live a natural lifespan and die of predation or disease. Of course, in the wild this would probably happen in the first five years or so, which is pretty short compared to a captive garter. That being the reason keepers can be so paranoid about the thiaminase issue, since we want them to live as long as possible

Well, when I was talking about goldfish's relatives I was thinking about whole Cyprynidae family.
Cyprinidae - Wikipedia, the free encyclopedia
As far as I know every member of this family contains thiaminase. Trouts are carnivores obviously and carnivore fish are generally thiaminase free. But they have to eat something. And my guess is: Cyprinidae are their prey... Or Cyprynidae just don't live in North America?

[d_virginiana]

Cyprinidae are definitely present in North America in large numbers, but I believe most (if not all) species are invasive; either released pets, food-fish, or escaped bait minnows. So even if the North American garter species are eating them now, my guess is they probably evolved eating mainly thiaminase-free native fish.

I think it's not something animals are necessarily immune to so much as they either don't eat it often or they live long enough to reproduce before it really affects them...

[Selkielass]

The great lakes are a highly disturbed ecosystem. Most sport fish are, if I
Understand correctly, species introduced to control previously introduced species that supplanted native species.

[Steveo]

I can't speak for wild populations, but I still struggle to get my pickeringii to eat anything other than silversides. He has taken worms and mice in the past, but he's also refused them more often than not. Seems to be doing just fine on a 90% fish diet.

I know that bass, sunfish, trout, and perch generally do not contain thiaminase, so there are many places in North America where a thiaminase-free fish diet would be possible.