Gulf Coast Ribbon Snake (Thamnophis proximus orarius) mating ball in January (winter) displaying stage III courtship behaviorm
In the previous blog we discussed how snakes’ breeding behavior is different in the Lower Rio Grande Valley (LRGV), and gave an example of the case of Leptodeira septentrionalis, Northern Cat-Eyed Snake, an attractive species unique to this region. Although the literature says they’re spring breeders, it seems that our field observations contradict that.

An even more drastic example of snakes that breed without brumating in the LRGV are Gulf Coast Ribbon Snakes (Thamnophis proximus orarius), they too, are supposed to breed during the spring. One day back in 2010 I was hiking through a small refuge and noticed a rather small mating ball consisting of about 8 snakes. This occurred in January, still winter, and the snakes were in full courtship behavior. Over the next few days I continued to observe them around the same “denning” site, which consisted only of a dense pile of branches. I documented this behavior and published it as the earliest reproducing snake in the country (Oyervides and Zaidan, 2014. Herp.Rev. 45(1):574). Over the course of the next few years I continued to monitor the behavior of this species in this region.

I’ve now learned that they breed year round. One would think that this would be detrimental to the snakes and they’d likely breed themselves to death in an effort to put out as many litters as possible, but it seems that’s not the case. Neonate and gravid Ribbon Snakes can be found year round in this region. In conducting my field surveys of these, I’ve also located a record size Ribbon snake, and one with a record size litter. Thus if they’re growing this large, having multiple litters per year doesn’t seem to be detrimental to them.

Their breeding behavior is also quite contrary to what the literature says, mind you, that last update on their biology was back in the 50’s by Tinkle. There is a very marked dimorphism between males and females of the species. When a female is being courted, she has several small males around her. These will follow her around and shadow her every move. Unlike in large mating balls where the males stress the females so much they practically force them into copulation, here, the female decides when she’s ready, as the males are too small to force her to do anything. These satellite males as I call them, will follow her around for days or weeks until she’s ready. Upon copulating, the males will disperse, and she will spend a lot more time up on tree branches absorbing as much sunshine as she can to speed up the process of having her first litter of the year and prepare for the next.
The advantage to this behavior is that because of the warm climate, there is a food supply for neonates year round. Moreover, their population numbers really decrease during years of drought. Having such a high number of individuals ensures that at least some will survive the droughts and restore a healthy population as soon as conditions improve. It’s amazing how sometimes we know so little of some of the most common species around!
Female with a male where the sexual dimorphism is evident.