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The Ambiguous Extinction of the Desert Slender Salamander

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The Desert Slender Salamander | Photo courtesy US Fish & Wildlife Service

One of the California desert's most unlikely inhabitants is missing. The desert slender salamander, declared endangered soon after its discovery in 1969 due to its restriction to two tiny canyon bottoms in the Santa Rosa Mountains, has not been seen in the wild since the 1990s. Still, wildlife biologists aren't ready to declare it extinct. At least not yet.

Salamanders aren't the kind of animal one usually associates with deserts. Some of their amphibian cousins have adapted to arid lands, the prime example being the spadefoot toad, which seals itself into a pocket of soil to outlast drought, emerging to feed and mate when it rains.

But salamanders are suited to moister environments. Most of them don't have the water conservation chops necessary to thrive in the California desert -- especially in the canyons ringing the Coachella Valley, one of the hottest places to be found in our deserts.

And at first glance, the desert slender salamander -- Batrachoseps major aridus -- wouldn't seem like an exception. A member of the plethodontid or lungless salamander family, desert slenders breathe through their skin -- which means they need to keep their skin moist in order to facilitate the exchange of oxygen and carbon dioxide, which means that if they dry out they suffocate. Which is not a useful trait in the desert.

Desert slenders avoid desiccation by sticking to sections of canyons where there's a bit more moisture. Their stronghold is -- or was -- one of the Santa Rosa's fabled fan palm oases, where canyons funnel water into narrow spots, geology forces it to the surface, and an overhanging canopy of foliage keeps the humidity a bit higher than it would have been. The salamanders thus survive in the desert by living in little outposts that aren't quite as deserty, where they eat any animal smaller than they are -- probably small ants and other microfauna, though no one has seen enough desert salamander mealtimes for us to really know how they get by. We also don't know how deep they tunnel into the soil, or how many eggs they lay at a time, or whether they maintain communal egg nurseries like other slender salamanders do. Basically, what we do know about desert slenders is that we don't know as much about them as we'd like.

Desert slender salamanders are very closely related to the garden slender salamander, Batrachoseps major major, a common denizen of coastal Southern California yards. They're very similar in appearance, about four inches long -- half of that length being tail -- thin, and dark. The desert slender has a slightly broader head than the garden slender, and its lighter color a bit more tinged with maroon. Most of us would need to have one of each in hand to tell the difference. When threatened, slender salamanders will either coil up or lift their tails in a defensive response: the desert slender is the only slender salamander that does both at once.

If you spend any time at all puttering around in Los Angeles gardens, especially those that get a little supplemental water, you've almost certainly encountered a garden slender, relaxing under a terra cotta pot or under the firewood. You may not have recognized them as salamanders: their legs are so small it's easy to miss them, and their grooved tails and general coloring give them the overall look of dark earthworms at first glance. But there are a lot of them, and of the 20 or so other species of slender salamanders in California. Slender salamanders are plentiful enough that you occasionally hear them referred to as the most common vertebrate in California.

Garden slender salamander | Photo: squamatologist/Flickr/Creative Commons License

Not so with desert slenders: estimates of the subspecies' total numbers seem to top out at around 500. The total known area of desert slender salamander habitat is less than two acres, most of it in Guadalupe Canyon near La Quinta -- and that canyon has historically low salamander density compared to the real desert slender hotspot in Hidden Palms Canyon near Palm Desert. Estimates of the salamander's population are just that, and the experts admit that their guesses may be off by a considerable margin. Desert slenders are hard to count. They're hard to find. They spend most of their lives hiding, much of that time literally underground -- in leaf litter, in animal burrows (including earthworm tunnels), and in between layers of rock outcrops, such as the thin, flat layers of a limestone outcrop in Hidden Palms Canyon.

Wildlife biologists do have some tricks to get them to reveal themselves. In 1986, after an unsuccessful day of looking for desert slenders, biologists Russell Duncan and Todd Esque returned to their campsite and found several under a tarp they'd placed under their gear. Struck with inspiration, they laid out plastic garbage bags in suspected desert slender habitat, then returned three months later at night with flashlights and looked under the plastic. This turned out to be a reliable way of finding individual salamanders without damaging their habitat. The area under the plastic stayed moister than the surroundings, and salamanders sought out its shelter. (You can do the same thing in a shady part of your yard if you'd like to see your local slender salamanders.)

Despite tricks like this, though, desert slenders remain reclusive and hard to spot. The desert slender was discovered when state game warden Russell Murphey started digging a watering hole for Peninsular bighorn sheep at the very limestone outcrop in Hidden Palms Canyon that was the salamander's main habitat. If he'd started digging a half mile in any other direction, we might not know about the salamanders today.

That highly restricted distribution -- the most restricted of any North American salamander, as far as we know -- may well have proved the desert slender's undoing. In 1976 a violent flood washed through Hidden Palms Canyon, scouring the canyon floor and scraping away most of the limestone sheeting and rubble in which desert slenders were previously found. Another storm in the mid-1980s removed most of the habitat that remained. There have been no desert slender salamanders found in Hidden Palms Canyon since 1996. The subspecies may have been wiped out there. Or it may be thriving, farther up the canyon wall among mosses and ferns, in a section of the limestone outcrop that biologists determined cannot be explored without damaging the habitat. Guadalupe Canyon's much sparser population may still be hanging on as well, but no one has seen any there for quite some time either.

That's partly because few people, if any, have looked. A 2009 review of desert slender salamander management by the U.S. Fish and Wildlife Service admits right up front that interest in the subspecies isn't what it used to be:

Over time, management of the [Hidden Palms Ecological] Reserve for the desert slender salamander has decreased as interest and management options have waned... The reserve management committee that was originally formed hasn't met since the mid-1980s. Monitoring of the population and habitat has not consisted of any more than periodic visits by CDFG biologists. Recent management has focused on clearing vegetation to create a safe watering hole for bighorn sheep.

Duncan and Esque looked for desert slenders in about three dozen likely canyons in the early 1980s, finding them only in low numbers in Guadalupe Canyon. Still, there are other canyons as yet un-searched. A State Parks staffer found two slender salamanders in a wetland at Anza Borrego Desert State Park: they may have been desert slender salamanders, or they may have been the closely related garden slenders. The area has not been thoroughly searched since, or at least not with any formal reports following.

So the desert slender may be gone, or it may be surviving undetected because we don't have the resources or the interest to look for it. But how did it get to such unlikely, precarious habitat in the first place?

When the desert slender salamander was first discovered, it was assigned to its own species: Batrachoseps aridus. About 10 years ago researchers examined the genomes of slender salamander species throughout California and Baja, and found that desert slenders and garden slenders were too closely related to constitute distinct species. But the large-scale differences between desert and garden slenders -- the desert slender's unique defensive behavior, as well as the smaller number of grooves in their tails -- were too marked not to be reflected in the terminology. They lumped them together as subspecies within Batrachoseps major.

The presence of distinct differences in morphology between two groups of organisms that are very similar in genetically is a hint that the two groups have diverged only recently. It may be only a few tens of thousands of years since desert slenders and garden slenders split into two distinct populations. Probably not coincidentally, it's only been about 12,000 years since the California desert was much more hospitable to amphibians. As the post-Ice-Age desert warmed and dried up the ancestors of today's desert and garden slender salamanders may have been forced out of most of their range in the newly arid desert, with most of the salamanders restricted to the lands west of the mountains, and a few hanging on by their tiny toenails in slightly moist desert canyons, depending on luck to keep their numbers going.

A few dozen desert slender salamanders may still go about their business in desert canyons we haven't bothered to search thoroughly. Or it may be that the desert slender salamander's luck ran out when floods scoured Hidden Palms Canyon over the last few decades, the nearly inevitable last blow from a climate that started to eradicate slender salamanders in the desert some 12,000 years ago. If the latter proves true, the desert slender salamander will have the distinction of being one of very few recent extinctions that may not be entirely our fault.

Chris Clarke is an environmental writer of two decades standing. Author of Walking With Zeke, he writes from Palm Springs regularly at his acclaimed blog Coyote Crossing and comments on desert issues on KCET weekly. Read his recent posts here.

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