Had a great hike on Sunday with Dom and Neil looking for timber rattlesnakes (Crotalus horridus). Here is a black phase rattler, the individual I became most attached to during the trip. She was very tolerant of us relaxing next to her lair. Several times she poked her head out in curiosity, tongue-flicking irregularly, then moseyed around slithering against the coils of her companion. We had amazing luck to witness interactions between the timbers. Scroll down to see more photos and descriptions!
As the female timber ceased rattling, we spotted a male ambling on straight towards the her. Despite all my time in the field, this was my first observation of an interaction between snakes. The male began twitching his head to the side, coming into contact with the female repeatedly as if he was measuring her response to his advances. Every time the female made a movement, the male would move in sync, possibly trying to coax her to stay. After resting his head on her body, he began circumscribe the female, tightening his coils as he wrapped around her. Unfortunately, it seemed that the female was too transfixed on our large human bodies as a threat (also evidenced by her previous rattling), so she was reluctant to release the tension of her body and permit the male to mate with her. Eventually, she slowly wandered off, and the male was left frozen in place surrounding a large empty circle. From then on, he seemed much more aware of our presence and gave me some unhappy head turns as I crunched around in the leaf litter. Timber rattlesnakes exhibit high site fidelity and rarely leave more than ten meters from their dens (at least for extended periods of time), so it’s unlikely that this failed opportunity for the male will be his last.
After we returned to the timbers’ lair, we heard a steady and slow rustling sound in the bushes. Peering through, we spotted a black female who coiled up and began rattling vehemently for about 15 seconds. During that time we kept hearing movement, and sure enough the tail end of this giant 4+ foot male moved just a couple of feet in front of us. Of the four individuals we saw, this yellow phase was by far the largest and most brilliant. In contrast to the others, several times he made an effort to look intimidating, turning his head rapidly to face me as I moved my arms, but not a single rattle.
If you look closely at the head, you’ll see blackened scales and a slightly disfigured rostrum. This is the result of snake fungal disease (SFD), a condition becoming increasingly threatening to wild snake populations in the last decade. SFD most likely originates from a naturally occurring saprobic fungus (Ophidiomyces ophiodiicola) that feeds on decomposing matter in soil. In 2006 a sharp population decline of New Hampshire timber rattlesnakes occurred, and ever since awareness and study of SFD has been on the rise. Numerous species of snakes have been documented to carry SFD, including rattlesnakes, milk snakes, rat snakes, and racers, but there are many gaps in knowledge of SFD ecology. Might the fungus be introduced or could the strain have recently acquired the ability to infect vertebrates? And have other factors including climate change or low genetic variation allowed the fungus to take a stronger hold? Even questions about transmission of SFD aren’t fully understood. Does direct contact between snakes facilitate transmission or is prevalence more directly associated with abundance of fungus in the soil? Because much is unknown, it’s important to minimize ways in which humans might aid the spread of SFD, especially handling or relocation of infected and even non-infected snakes where symptoms may be less apparent.
Fortunately for this individual, it seems that he is over the hump of the fungal infection. When fresh, the wounds are often red and white because due to the exposed damaged tissues. On the other hand, the black and purple scarred tissue on this individual were probably from a much older infection. Dom, our New England timber connoisseur, suggested that the male has likely already overcome the infection from this potentially fatal disease.
From my other timber rattlesnake photos, you probably want to see the iconic rattle. Here is a young adult black phase rattler showing off her slender and intact rattle. Growing up, I always thought the rattling sound was produced similarly to a maraca, where free floating granules of would rake the sides of the keratinous structure. Rather, the rattle consists of interlocking hollow segments, and the ridges of each segment rub together to create a buzzing sound, mechanically much like a grasshopper’s stridulation. One of these segments is added each time the snake sheds its skin, and the very first segment it is born with is called the button. Without other segments to rub against, a lone button cannot produce a rattling sound. I’ve seen neonates before in the wild that furiously tremble their tails, and it’s comical and strange for the motion to be accompanied by silence.
