I’m aware that the T. sirtalis pallidulus is active farther up north that T. sirtalis sirtalis, however in the new England area there is some overlap, how does one make a distinction between the two subspecies?
I have posted this answer elsewhere too:
I usually tag one of the top identifiers with a request to contribute on an observation. If they are responsive, which they usually are, I then ask for resources on how to identify better. This works great for me!
The two subspecies are best differentiated by range.
(Not a perfect range map, but it works.)
Where the two subspecies border each other, they often intergrade. Because of this, I’m usually hesitant to put a subspecies identification on common garters in VT, NH, northeast MA, and southern ME.
In terms of physiological differences, I find that T. s. pallidulus is slightly duller and less vibrant than T. s. sirtalis. There are likely some research papers online that delve more in depth into subspecies distinction, but I haven’t seen many personally. If I do find any, I will post again here.
I hope this helps!
it did thank you, the observation I saw was in that overlapping range.
I’m glad you found it useful :)