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California's Ten Most-Endangered Species

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At extinction's door; the Amargosa vole | Photo: UC Davis
At extinction's door; the Amargosa vole | Photo: UC Davis

People once had no concept of extinction. During the Renaissance, philosophers argued that the animals that fossils represented must still be alive somewhere in the planet’s unexplored regions, as a benevolent Creator certainly wouldn’t let any of His creations die out. This view held sway even as recently as the 19th Century: Thomas Jefferson, who had written a scientific treatise on fossils of a giant ground sloth, instructed explorers Meriwether Lewis and William Clark to keep their eyes peeled for ground sloths west of the Missouri.

That’s despite the fact that Western science had a solid example of extinction by the early 1700s. The year 1662 was the last time anyone reliable recorded a sighting of a certain flightless bird on the island of Mauritius; by the mid-19th Century, scientists realized that that bird — the dodo — had in fact been wiped from the face of the earth by human activity.

Since then, we’ve gotten a lot more familiar with the concept of extinction. All species go extinct eventually — by dying out or evolving into something else — but we’ve sped that process up to perhaps several hundred times its normal rate. How? By consuming more and more of the planet for our own purposes.

The whole idea of endangered species is based on extinction: an endangered species is one for which extinction looms. And since California is not only home to more than its share of unique species but also a place where development has changed a majority of the state’s landscape, it makes sense that quite a few California species are facing extinction. Some of them are closer to death's door than others.

We’re billing this as a “ten most endangered species” list for the state, but that’s obviously a subjective assessment. There are plenty of other species that could have made the list as well, and this list might even provoke argument among conservationists who consider other species to be in more trouble. As one conservation professional said to us as we prepared this article, “there are a lot of endangered species tied for first place.” As a nod to this subjectivity, we've listed other species for each entry that could reasonably have been profiled instead.

Photos of Tropidocarpum californicum are almost as rare as the plant. | Photo: Dr. Dean Wm. Taylor, some rights reserved
Photos of Tropidocarpum californicum are almost as rare as the plant itself. | Photo: Dr. Dean Wm. Taylor, some rights reserved

Kings gold (Tropidocarpum californicum

This yellow-flowered plant in the cabbage family is a classic example of the kinds of things that make push some California plant species toward extinction. It was likely never very abundant, and its specialized habitat has been more or less destroyed. In the case of Kings gold, that habitat consists of alkaline soils along the south shore of what was once Tulare Lake, which hasn't existed except in very wet years since the 1940s.

As you'll see with examples further along in this list, the dramatic degree to which we've altered the vast majority of the Central Valley, from its bottomlands plowed and replowed, to its rivers plugged with giant concrete dams, make this center of California far too well-represented on any list of California species in peril.

And Kings gold may be the worst-off of the lot. Though there’s some hope for finding a couple as-yet undiscovered populations of this spring-blooming annual, at the moment it’s known only from one patch near Interstate 5 west of Wasco. In 1999 botanists counted just 50 individual plants in that patch, and the species’ numbers haven’t really grown since.

Kings gold’s habitat is, naturally, threatened by development, ranging from suburban sprawl and agriculture to renewable energy projects.

Other critically endangered California native plants: Tiburon mariposa lily, white-margined penstemon, Lane Mountain milk-vetch, Refugio manzanitaFranciscan manzanita, and many more.

Delta smelt |  Photo: USFWS/John Ridilla

Delta smelt (Hypomesus transpacificus)

We’ve written about the Delta smelt a lot here, as it’s the unlikely focus of some of the nastiest California water-related political battles. The smelt, which evolved in the Bay-Delta brackish zone where snowmelt from the Sierra Nevada mingles with tidal water from San Francisco Bay, can tolerate only a narrow range of salinity.

Since we started pumping significant amounts of fresh water out of the Bay-Delta system before it can counter the tides, salt water has penetrated farther inland, which has degraded the smelt’s brackish habitat.

It also doesn’t help that they get chewed up in pumps, or that they get eaten by introduced fish, or that invasive clam species are out-competing the smelts for their zooplankton food.

It’s entirely possible that the smelt has declined past the point of recovery. Fishing boats used to haul Delta smelt up by the ton to sell them in San Francisco markets; now, perhaps a few dozen remain in the entire Delta. And if the fish are declared extinct sometime soon, there are those who would celebrate.

Some other Sacramento River fish in serious trouble: longfin smelt, Sacramento perch, Sacramento split-tail, green sturgeon, and the Sacramento River winter-run Chinook salmon, which gets its own entry below.

Endangered Amargosa vole bred in captivity in Fall 2014 at UC Davis | Photo: Don Preisler/UC Davis School of Veterinary Medicine

Amargosa vole (Microtus californicus scirpensis)

This little critter — possibly the most adorable of California’s critically endangered species — made news early in 2015 when a group of captive-bred voles slated to be released into their traditional habitat along the Amargosa River died on the way there. Grief-stricken biologists determined that the voles had died from a combination of dehydration and stress — a bit ironic for a rodent that’s native to one of the most stressful, dehydrated landscapes California has to offer.

The Amargosa vole subsists on a diet consisting almost entirely of three-square bulrush, a very heat tolerant wetland plant that grows around springs in the vicinity of the Death Valley community of Tecopa. A mixture of groundwater pumping for agriculture and development, a drying climate, and direct human disruption of the bulrush marshes has reduced numbers of the Amargosa vole, which persists in just a handful of those marshes. In 2013, the vole’s main stronghold — a large marsh along the Amargosa — suffered almost a complete drought-related dieback, putting the vole in serious danger of extinction.

That’s when biologists at UC Davis, working with a number of government wildlife agencies and non-profit preservation groups, started breeding the voles in captivity and studying how best to preserve their bulrush habitat. Here's a video the captive breeding team at UC Davis created to explain, and fundraise for, the project. Trigger warning for adorable rodents.

A later release in 2015 proved successful, and the groups are working together to improve conditions in in the marshes. But this desert vole isn’t out of the woods: one cigarette carelessly tossed into the bulrushes by an incautious tourist might still badly damage the vole’s population. As could one month's activity by an outdoor cat.

Other California rodents we could have mentioned here: salt marsh harvest mouse, San Bernardino kangaroo rat, riparian woodrat, San Bernardino flying squirrel, Pacific pocket mouse.

Tricolored blackbird | Photo: Monte Taylor, some rights reserved
Tricolored blackbird | Photo: Monte Taylor, some rights reserved

Tricolored blackbird (Agelaius tricolor)

Of all the songbirds in North America, the tricolored blackbird — a close relative of the far more common red-winged blackbird — is the most gregarious. Its native range restricted almost entirely to California, the tricolored gathers in huge flocks during its nesting season in early spring, with tens of thousands of birds in a single 10-acre field not at all unusual.

That puts the tricolored in extreme danger, as the Central Valley population of tricolored blackbirds — the species’ stronghold — tend to nest in grain fields right about the same time that farmers want to harvest those grains. That means that a couple hours’ work with a combine might kill 50 or 60 thousand of the birds at once.

Though it may seem odd to mention a bird like the tricolored blackbird, which numbered around 145,000 individuals the last time a statewide count was done in 2014, with species like the Amargosa vole and Kings gold, with just a handful of individuals left. But it’s that very abundance that makes the tricolored blackbird’s decline most worrisome. Those 145,000 tricoloreds was a 44 percent decline from the species’ numbers in 2011, which were themselves down by more than a third from 2008. (A new survey is being done in Spring 2017: here’s hoping that it brings better news than the last two did.)

It’s no accident that bird conservationists call the tricolored blackbird “California’s passenger pigeon.” The species was once incomprehensibly abundant, with many millions filling wetlands and grasslands from southern Oregon to Baja. And now, one afternoon’s work on a Central Valley triticale farm could nearly wipe the tricolored from the face of the earth.

Conservationists have been urging wildlife agencies to protect the tricolored blackbird under the state and federal Endangered Species Acts. Those efforts have not brought permanent protection so far.

Other songbirds we could reasonably have mentioned: coastal California gnatcatcher, yellow-billed cuckoo, southwestern willow flycatcher, island loggerhead shrike.

Buena Vista Lake ornate shrew | Photo: USFWS
Buena Vista Lake ornate shrew | Photo: USFWS

Buena Vista Lake ornate shrew

Don’t call this beady-eyed, long-tailed, four-inch denizen of the Tulare Basin a rodent. Rats and mice and squirrels are actually much more closely related to you and me than they are to the Buena Vista Lake ornate shrew, one of nine subspecies of ornate shrew native to California.

What do "Endangered" and "Threatened" mean?

Native for now, that is. Fewer than three dozen Buena Vista Lake ornate shrews have been seen since 1990.

The problem? As with so many other wildlife species native to the Central Valley, the shrew’s habitat has been almost entirely destroyed. Before the 20th Century, rivers draining the southern Sierra Nevada filled the Tulare Basin with runoff every year, feeding lakes like Tulare Lake, as well as the lake from which the shrew takes its name. Now, Tulare Lake exists only during exceptionally wet years (like early 2017, in fact), and Buena Vista Lake isn’t much more than a sump, tainted with agricultural effluent.

Whatever Buena Vista Lake ornate shrews still exist — if any still do — eke out an existence in the Tulare Basin’s few remaining wetlands, which cover less than five percent of the area they occupied a few human generations ago.

Assuming there are any left, they subsist on insects and other invertebrates, a bit of water as yet not diverted to row crops and almond orchards, and the attention and goodwill of the few Californians that have ever heard of them.

Other California mammals that deserve mention here: riparian brush rabbit, San Joaquin kit fox, Humboldt marten, Townsend's big-eared bat

Desert slender salamander | Photo: USFWS

Desert slender salamander (Batrachoseps aridus)

Here’s another species that may actually be extinct: no one has recorded seeing a desert slender salamander for 21 years. Not that people have spent a lot of time looking.

Known only small seeps in two canyons in the Santa Rita Mountains in Riverside County, the desert slender salamander likely evolved as drying conditions over the last 12,000 years or so isolated their ancestors from their close relatives along the moister coast. Belonging to the large group of amphibians known as lungless salamanders, slender salamanders breathe through their skin. If that skin dries out, oxygen and carbon dioxide can’t diffuse in an out of the salamander’s bloodstream, and they die.

Which puts desert slender salamanders in a precarious position. They can survive near seeps and springs, if they have piles of loose talus that provide moist hiding places. But if those isolated salamander oases dry out, it’s not like the desert slender can set off across the countryside in search of more habitable surroundings.  

Discovered in 1960, the salamanders have only ever been found in Guadalupe Canyon and Hidden Palms Canyon near Palm Desert. Biologists have periodically looked for the salamanders over the years, but a five-year status review of the species done by the U.S. Fish and Wildlife Service in 2009 says that there haven’t been any documented sightings of the delicate beasts since 1996.

And it looks like no one’s looking. USFWS ruefully admitted as much in that 2009 status review, when it said of the population at the Hidden Palms Canyon reserve, “Over time, management of the Reserve for the desert slender salamander has decreased as interest and management options have waned.”

There may be desert slender salamanders living undetected in either Hidden Palms or Guadalupe canyon, or in as-yet undiscovered seeps elsewhere between the Coachella Valley and Anza Borrego. Or they might have gone extinct during the Clinton administration. And we may not ever find out which is the case.   

Other amphibians we could have profiled: arroyo toadsouthern mountain yellow-legged frog, Sierra Nevada yellow-legged frog

Lange's metalmark butterfly | Photo: USFWS
Lange's metalmark butterfly | Photo: USFWS

Lange's metalmark butterfly (Apodemia mormo langeia)

At first glance, the gritty Bay Area city of Antioch might seem an unlikely place for endangered species to call home. A history of polluting industry layered over with a few decades’ worth of sprawl makes this gateway to the Delta seemingly indistinguishable from any number of less-affluent cities elsewhere in the state.

But Antioch is home to a few endangered species found nowhere else. And among them, a striking black and orange butterfly flitters perilously close to extinction.

The Lange’s metalmark butterfly utterly relies on one plant — the Antioch Dunes buckwheat — for its larval food supply. The Antioch Dunes buckwheat is found only at — you guessed it — the Antioch Dunes, a small patch of sandy hills along the south shore of the San Joaquin River. Those dunes were unfortunately convenient for brick-makers who mined much of the dunes’ sand, especially as California rebuilt in the wake of the 1906 San Francisco earthquake and fire.

No one’s mining the dunes anymore: the 55-acre parcel, also home to the Endangered Antioch Dunes evening primrose and Contra Costa wallflower, was protected in 1980 as a National Wildlife Refuge closed to the public. But the Lange’s metalmark is still in trouble. Its larval food source only germinates in open sand, such as you might find in an actively evolving dune system. But a number of invasive plants have stabilized the dunes, reducing the amount of open sand available.

That pushed the Lange’s almost to extinction a decade ago: in 2006, just 45 adults were counted during the species’ mating season. Biologists have successfully bred the butterfly in captivity since then, and have reintroduced captive-bred adults and larvae to the dunes to boost the Lange’s numbers.

That’s good news, but until scientists learn how to control the invasive plants covering the dunes without hurting either the butterfly or the buckwheat it relies on, the Lange’s will remain in the endangered species equivalent of Intensive Care.

Other California arthropods in big trouble: Shasta crayfish, Delhi Sands flower-loving fly, Ohlone tiger beetle, Zayante band-winged grasshopper, San Diego fairy shrimp