Snake Longevity

The Age-Old Old-Age Question

How long do they live? is one of the most common questions we get from the public about snakes. It might seem simple to estimate, but lifespan is influenced by many factors. I love this question because it is a good lead-in to ecological concepts and, of course, stories of individual wild snakes. And as we all well know, stories are a great way to relate to other beings.

Red Diamond Rattlesnake (red rattlesnake with white markings) coiled in a resting posture
Double Y, a male Red Diamond Rattlesnake, was first observed in 1993, when he was at least three years old. He was seen 11 times over the next 23 years, most recently in 2016, when he was nearly 30 years old! (Photo and data courtesy of John Porter.)

I usually start with differentiating how long do they live from how long can they live. Can implies a maximum potential age, whereas do suggests a typical lifespan. Unlike humans, most snakes do not even survive to maturity, let alone old age. The hazards are many; smaller snakes are assumed to have more predators, and juveniles usually have weaker defenses and less knowledge of their landscape (e.g., good places to hide and hunt; it also helps explain why young snakes are often so quick to react to threats). Some young snakes may be instinctively driven to disperse into distant terrain, a risky endeavor that has a tiny chance of a big reward — outbreeding, say, or perhaps even colonizing an available niche.

To persist into adulthood, snakes usually need to be well-attuned to their particular home and its prevailing conditions. And when something works, there is little reason to change tack — adults have pretty stable home ranges across years, returning again and again to favored spots to hunt, shed, overwinter, and find others of their kind, all while avoiding or defending against attacks from mortal enemies. This simple recipe for longevity is probably best served in relatively stable environments, where prey and mates can be reliably encountered. (But as weather variability and landscape alteration increase, past experience may become a poor guide for long-term survival.)

There are thousands of snake species, ranging from about a gram to 100 kilograms, and old age for one might be when another is just getting started! And although longevity roughly scales with body size, other ecological factors and ancestry can be significant influences.

At the “fast” end, some species that reach maturity at one year might be considered old at, say, five. Data for longer-lived species are much harder to come by, as they require tracking individuals over decades. These data often come from captives, but occasionally a field study turns up an individual marked or recognized from many years before (see Old Friends below). Individuals of many species have lived to thirty years, and there are suggestions that some, like Rubber Boas and Timber Rattlesnakes in their high-latitude forest habitats, could survive to fifty! There is no doubt that new records will build our knowledge of how long snakes can live.

Age is just a number, as they say. But behind that number is a lifetime, one filled with triumphs and narrow escapes, comforts and even delights. When I come across an old snake, whether I’ve seen her before or not, I wonder about her adventures and ordeals, the stories behind her scars or missing tip of her tail. I wish her luck in the future that lies before her, that her wiles may guide her safely to fulfill her humble needs, and maybe, just maybe, I’ll see her again.

Old Friends

Willie

Black-tailed Rattlesnake (yellow rattlesnake with dark brown blotches) draped over a cottonwood log in a hunting posture
Willie hunting on a giant Cottonwood log, June 2012.
Black-tailed Rattlesnake (yellow rattlesnake with dark brown blotches) hunting against a cottonwood tree
Willie hunting against an ancient Cottonwood Tree, May 2023.

We first met Willie, a Western Black-tailed Rattlesnake, in June 2012, hunting on a massive downed Cottonwood Tree. We didn’t handle or mark him, but Jeff got excellent photographs. Black-tailed Rattlesnakes have unique head patterns that can be used to identify individuals and Willie also has two blotches on his back that are connected. Last May we ran into him again, hunting against an ancient Cottonwood Tree. Those blotches caught our eyes and we soon matched that head pattern to our friend from 11 years ago. Willie was a large adult in 2012, so he’s likely in his 20s now, at least! Willie was in excellent condition last May, which made us wonder: how many other decades-old rattlesnakes have we met?

TWA

Pregnant TWA, Arizona Black Rattlesnake, 2011
Pregnant TWA in May 2011.
TWA, female Arizona Black Rattlesnake, with one of her newborns, September 2019
TWA with one of her newborns, September 2019.

We first met a clearly pregnant Arizona Black Rattlesnake, TWA, in the spring of 2011 at the outset of our study of their social behavior. She was the biggest, oldest mom that year — and every year we visited since. Nearly as large as any adult male in that population (males of this species are usually larger than females), her long, non-tapering rattle indicated she stopped growing long ago.

TWA often shares her nest with younger moms and, as is usually the case, sticks them with the child care duties. In fact, in 2011, 2013, and 2015, we never observed her with her kiddos. They were always with the babysitter. But on our last day at that site in 2019, we finally saw TWA with one of her babies.

Based on what we’ve learned about this population, TWA was (at least) in her early teens when we met her in 2011, so she was pushing 20 years old in 2019 and still producing big, healthy litters.

Old Lady Racer

This North American Racer was first caught and marked in 2010 as a small juvenile that likely hatched the year before. We didn’t see her again until 2014, when she showed up as an adult, 1.3 km away from her initial capture location. We sporadically recaptured her at different traps on the same hillside that appeared to be her chosen home range until 2021, at which point she had grown into one of the largest racers we have seen on site at 1 meter in total length, and was 12 years old. Despite heavy scarring and her old age, she appeared very healthy and was hopefully gearing up towards reproducing later in the year.

Photo and data courtesy of Elliot Schoenig, USGS

North American Racer (slender dark green snake) held in a white hand
Old Lady Racer photographed by Elliot Schoenig, USGS, in 2021.

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