Squirrel!
Mohave ground squirrels at a camera trap bait pile. Not shown: “Free Skwirl Fud” sign. Photo by U.S. Army Engineer Research & Development Center
It’s a year old, but I just read a paper on one of those species that pops up pretty frequently in environmental impact reports — the Mohave ground squirrel, Xerospermophilus mohavensis — whose conclusions add a little bit more depth to the Deep Time perspective of the desert around here. And by “depth” I mean “epic stories.”
And by “around here,” I mean “at least 45 miles northwest of here”: the Mohave ground squirrel’s range is all on the other side of the Mojave River, aside from a strip of land a few miles wide along the north desert foothills of the San Bernardino Mountains, where it mostly hasn’t been seen for the last few decades anyway. The squirrels’ historic range was somewhere in the neighborhood of 7,000 square miles or 20,000 km2, depending on which authority’s rounded-off guesstimate you use.
The Mohave ground squirrel is a foliage and seed eater — you may have guessed that second part from “Xerospermophilus,” which essentially means “desert seed lover.” It’s about nine inches nose to tail, short-haired, roughly ground-squirrel-shaped, ranges in color from pinkish to gray to cinnamon, in a more or less solid-colored coat. The species is rare throughout its range, which is shown in the U.S. Fish and Wildlife Service map embedded below:
That map is from the Federal Register, dated October 2011, in a “Finding” that the squirrel didn’t warrant protection as endangered or threatened under the U.S. Endangered Species Act. That finding was more politics than science. The squirrel is threatened by urban and industrial development, off-road vehicle use, and by climate change. Under CalESA, the California version of that law, the squirrel is listed as “Threatened”: the IUCN classifies the species as “vulnerable.”
The authors of the paper I mentioned up top, K.C. Bell and Marjorie Matocq, wanted to learn more about historic habitat colonization and connectivity among Mohave ground squirrel populations. They sampled nuclear and mitochondrial DNA from 258 individual squirrels collected in 13 locations throughout the species’ range, then charted the genetic diversity among the samples. They also sampled nearby populations of the closely related round-tailed ground squirrel, Xerospermophilus tereticaudus, and some suspected hybrids between the two species.
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