I wouldn't label myself a "breeder" but I do have some experience with breeding garters. I think it is kind of interesting that we often (at least every breeding season it seems like) have this debate of what captive litters are, compared to their wild counterparts. Every possibility in the book is thrown out there as to why there seems to be so many more jellies and stillborn babies in captivity. It may be one cause, it may be a combination of multiple causes, but I find it interesting that the "natural" methods these snakes use to reproduce are rarely brought up. It has been shown in multiple studies that garters are a multiple paternal species. This study,

Multiple Paternity in Wild Populations of the Garter Snake, Thamnophis sirtalis, James M. Schwartz, Gary F. McCracken and Gordon M. Burghardt, Behavioral Ecology and Sociobiology, Vol. 25, No. 4 (1989), pp. 269-273,

estimates that up to 73% of garter litters exhibit multiple paternity. I don't often hear this as a possible reason for the number of jellies and stillborn babies in captivity. We know that in the wild garters are involved in mating balls; how many of us provide "mating balls" in captivity?

Personally I am still not convinced that there is any greater number of jellies in captive breeding when compared to wild breeding, but if there is I would attribute the overall higher number to the lack of multiple paternal mating. The other reasons many of you have mentioned may be reasons for individual situations, but if I were to paint all garters with a broad brush, I would start with multiple paternity.

The fact is, one of the reasons garters are so successful in the wild is because they have built-in ways to skew percentages of possible problems that may be manifested through simple Mendelian genetics (there is a paper on that as well, I can dig up the source of that if anyone is interested). I don't see it as coincidence that we, for the most part, go against these tendencies by trying to force garters to fit into the mold of simple Mendelian genetics, and then wonder why it doesn't always work.

Just my thoughts.

-Thomas Wilder