Rattlesnakes increasing in California


This article claims rattlesnakes only need 500-600 calories per year. That seems wrong based on what I ~think~ I recall about how much captive snakes got fed when I worked at a nature center years ago.

Does that seem valid to those of you who know herps?

Also, I’m not sure I believe the scale of population increase indicated in the report. Seem reasonable?


I don’t have any personal expertise but I know the authors of the cited paper and can vouch that they are excellent scientists. Ectotherms need stupidly low caloric intakes to survive, though as the authors note, they do need more to be more active, etc. It doesn’t look like the author of the SFGate article actually read the paper, just cited a press release (which isn’t even particularly new at this point!). But the relevant link is here: https://wayback.archive-it.org/6191/20221009144147/https://calpolynews.calpoly.edu/news_releases/2021/june/rattlesnakes-may-like-climate-change-cal-poly

And the section is:
The research team discovered that the snakes use energy extremely efficiently. To subsist, an adult male rattlesnake needs only 500-600 calories for an entire year, which is about one ground squirrel, the equivalent of only about half a large burrito. Though in the real world a rattler needs additional calories to hunt and bear young among other activities, the calculations point to the snakes’ ability to survive even if prey isn’t plentiful. Humans, by comparison, need about 1,300 times as many calories to survive.

“Rattlesnakes require very little energy to exist,” said Crowell, who earned a master’s degree in biological sciences at Cal Poly.


Science journalists who actually read and understand science are increasingly rare, and I’ve never seen anything from sfgate.com that would suggest they care about getting it right. Just this sentence, “the snakes are thermoregulators, which means they are able to change their own body temperature to suit their surroundings,” is strong evidence that that the journalist doesn’t understand the science.


since this isnt a topic about iNaturalist, I moved it from General to Nature Talk


I can’t speak for California but I’m skeptical of the claim that rattlesnakes have recently increased significantly in numbers anywhere. I’d want to see better data to support that claim. What is real is that people may encounter more snakes at certain times in certain places due to a change in weather conditions (e.g, rains following drought) or increased human presence in some places. All snakes can “disappear” during periods when conditions are not good then appear when they are. In my area (New Mexico) we routinely get reports of rattlesnakes suddenly increasing in places in late summer or fall when the heat of summer has abated and snakes may be moving towards dens during daylight.


Kind of a standard clickbait SF Gate headline that says “Why California’s rattlesnake population is booming” but the article doesn’t really say that. Both the press release and the article itself don’t go that far when citing the paper/press release. Below is a quote from the article (emphasis mine):

the seven species of rattlesnakes found in California could experience more growth as other native animal populations shrink

It’s basically just saying that with climate change, the rattlesnake populations could increase in California but doesn’t say it has increased, aside from quoting one person with anecdotal evidence. California has seen a lot of housing development into areas where rattlers live, more people are out hiking, and I would imagine fewer people kill them outright and instead report them to snake removers, so there are a lot of confounding factors that one would have to deal with before making any claims on population increase, I’d think.


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