Thamnophis scalaris is a small, rare and very beautiful species of Garter Snake from central Mexico. Adult females are usually between the 42,3 cm (Manjarrez, J. et.al., 2007) and 60 cm total length.
Not much is known about the reproductive biology of this species. In November 2019 I witnessed mating behavior in my Thamnophis scalaris breeding group. Thamnophis scalaris has a reproductive cycle that is very different from the members of the genus Thamnophis originating from the US and Canada. Mating season is probably (this has not been investigated in detail) somewhere in late fall (October/November) and in the wild most females are already pregnant end of November (personal observations).
The females likely stay active during the wintertime (at least on warm and sunny days in some populations at lower elevations, but also this not well investigated).
Babies were born between June 1st and June 17th in a population studied near Toluca, Mexico (Manjarrez, J. et.al., 2007).
Sunday November 17th 2019 late in the afternoon I noticed male 1 actively copulating one of the females (female 1). His body was lying beside the female’s body and they were clearly locked. Little shocks went through the body of the male. In the beginning I could not see the head of neither the male nor the female and of course I did not want to disturb them.
A little later the female was slowly crawling through the cage and I saw both their heads.
Now I noticed that the male had his jaws around the neck region of the female.
I cannot be sure whether the male was “biting” the female during the entire duration of the copulation.
About 10 minutes later the pair unlocked and the male resumed to basking.
The female disappeared a little later.
All the time while the pair was copulating a second male (male 2) also attempted to mate with the same female. He was not interested in one of the other females (female 2) that was also active at that time.
Male 2 had his chin on the back of the female, crawled towards the tail region in quite high speed, turned around and searched for the head of the female. Once they were lying like this side by side, with the male on top, the (much) smaller male crawled back in the reverse trying to bring his cloaca close to the cloaca of the female.
This part of the behavior is quite similar in appearance to the mating behavior of other member of the genus Thamnophis. Maybe a small difference is that the T. scalaris male 2 was doing this very active and rapid with relatively high speed and precision.
What is very unique and never mentioned in literature before is that T. scalaris males are biting the females during courtship. I witnessed this second male (male 2) trying to bite the female several time while he was slithering back and forth over the female. While at the same time male 1 who was locked also had his jaws around the neck of the female.
It is not very often that one discovers a never described aspect of behavior. F.Tews (personal comment) was the first to witness this behavior and filmed this behavior last year in 2018. I was very thrilled to also witness this in my breeding group for the first time.
November 18th-27th I was away so I could not check on my T.scalaris breeding group, but at 7 PM of November 28th I could witness male 2 trying to mate with female 1, biting her regularly.
November 30th a third male (male 3) tried to mate with female 1 and he had bitten her in the tail region.
On December 4th I saw male 2 attempting to mate female 1 once more. After December 4th till December 29th (when I wrote this short article) I could not witness mating activities anymore.
So all 3 males have shown mating activities towards female 1 and all 3 males have bitten her during these attempts.
I have not seen any mating attempts towards the other females that live in the same cage.
So now the long waiting starts. Hopefully the mating attempts have been successful and baby T.scalaris will be born in springtime.
Manjarrez, J., C.S. Venegas-Barrera & T. Garcia-Guadarrama, 2007. Ecology of the Mexican Alpine Blotched Garter Snake (Thamnophis scalaris). The Southwestern Naturalist, Vol. 52. , No. 2: pp. 258 – 262