Black Rat Snake

Black rat snakes (Pantherophis obsoletus) undergo a stark transition in coloration from juveniles to adults. When young they are mostly beige with blotched brown patches along the dorsum and fainter smaller ones along the sides. As they mature, the belly stays cream white while the rest of the body darkens into a jet black color, so dark that when spotting this individual heading under dense grass cover I thought it was a shadow. In many snakes, hidden color patterns of the juvenile stage or even of related species are visible in the skin underneath the scales. I’ve noticed this especially in many solid-colored vipers that have faint stripes upon closer inspection. In black rat snakes, similarly, traces of the juvenile coloration are usually detectable as an underlying reddish checkered skin pattern. When backing up to view the snake as a whole, it’s impossible to unsee those subtleties, making the snake almost seem like an entirely different animal. Black rat snakes also have bright white lines at the edge of some scales, extending diagonally. In many snakes, conspicuous scale edges are used in predator deterrence, concealing them at rest and exposing them when the body is inflated defensively. However, I haven’t heard of this proposed in black rat snakes, and it seems that even when in a non-threatening posture, the white scale tips are visible.

Rat snakes are adept arboreal hunters, climbing up vertical trunks of any orientation. This is partly due to their ability to create two venterolateral keels, making the snake’s body less cylindrical to prevent slipping. When in need of greater traction, the head turns from side to side after contacting dips in the substrate. On those inflection points, the body also flexes and tightens for enhanced support. While these behaviors are used for traversing smoother surfaces, it’s just as common to see them slither up in a straight line, seemingly defying gravity. Their arboreal prowess allows rat snakes to be successful predators of birds and bird eggs, but they feed on a variety of prey, including lizards, frogs, rodents, and rabbits.

Although rat snakes are generally docile, this one gave me a spectacular display when caught. It gaped the mouth widely to expose bright pink colors and began striking the tail repetitively against my arm. Many venomous and nonvenomous snakes will perform a ‘tail-rattle’ in response to a predatory threat. A particularly memorable one for me was a juvenile fer-de-lance (Bothrops atrox) in Brazil that produced a noticeable fluttering sound in the leaf litter. In the future hopefully I will be able to film this behavior in situ, and I’ll follow up with another blog post.

Photographed after capture [5]

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