S5E26: Maps, Vanished Lakes, and Two Desert Squirrels

[00: 00: 00] Chris Clarke:  90 Miles from Needles, the Desert Protection Podcast is made possible by listeners just like you. If you wanna help us out, you can go to 90milesfromneedles.com/donate ortext Needles to 53555.

[00: 00: 25] Joe Geoffrey:  Think the deserts are barren wastelands? Think again.

[00: 00: 34] Joe Geoffrey: It's time for 90 Miles from Needles, the Desert Protection Podcast.

[00: 00: 45] Chris Clarke: Thank you, Joe, and welcome to90 Miles from Needles. I'm your host,Chris Clarke, and today I wanna tell you a story about an epic that took place in the Mojave Desert and encompasses tens of thousands of years at the very least. We'll get to that in just a second. Very briefly, though, I want to thank our newest donor, Cheryl Cox, for signing on as one of our recurring donors.

[00: 01: 09] Chris Clarke:  Cheryl, thank you so much. If you wanna join Cheryl, you can go to 90milesfromneedles.com/donate and pick an amount and a frequency of donation that makes sense to you from $1 one time all the way on up to 1,000 bucks a month or more. And now let's get to the story. Are you sitting comfortably? Good. Then I'll begin.

[00: 02: 00] Chris Clarke: I've always been intrigued by maps ever since I was quite small. I went to school in classrooms that had gigantic paper maps of the world hanging on the wall. Unsurprisingly for people that know me, I often missed many minutes at a time of what the teacher was saying 'cause I was looking at the map. If I hadn't done that in calculus class, I might have a badly paying job as an adjunct science faculty member, but that's foranother time. Looking through history books back then, I was intrigued at how maps change, how they shift, and how those splotches of color on the maps change shape and then sometimes wink out entirely as years go by.

[00: 02: 45] Chris Clarke:  The Austro-Hungarian Empire was there, and then it wasn't. And even as a kid, I knew it wasn't just being changed 'cause people got tired of writing Austro-Hungarian Empire on their mail and decided instead to lose the hyphen and become either Hungary or Austria. There was political intrigue involved and regional disaffection, and somewhere in there, an archduke got assassinated.

[00: 03: 12] Chris Clarke:  There's always a story behind the shapes on the maps, and there's always a story when those shapes change. A map is, at best, a snapshot of whatever it is we're mapping at that precise moment in time. And like political maps, other kinds of maps have stories, too. Look at a map of the desert Southwest, and you may see that a wilderness area or a national park or a national monument or a wild and scenic river will have odd geometry in its outlines on the map.

[00: 03: 45] Chris Clarke:  There might be little pockets of one thing surrounded by another. There might be unexplained sudden right angles, omissions, additions. Each one of those little idiosyncrasies in the map has a story behind it. Maybe there was a preexisting mine, and whoever designated the national monument had to exclude the mine and the road that leads to the mine from the national monument.

[00: 04: 09] Chris Clarke: That's generally called a cherrystem. A cherrystem is a result of someone objecting to a boundary or of people anticipating objections to the boundary and not wanting to deal with those objections. Sometimes the squiggles on a map change due to land ownership. During the 19th century, theU.S. government incentivized companies to build railroads joining the coasts by giving the railroad companies a huge amount of land throughout a lot of the West.

[00: 04: 38] Chris Clarke: Every other square mile was given to the railroad. That's called checkerboarding. And railroads did a bunch of different things with that land. They held onto it, or they sold it a little bit at a time to private owners, or they sold many square miles at a time to logging and mining companies. In Palm Springs, the Agua Caliente Cahuilla Reservation is checkerboarded across the valley.

[00: 05: 06] Chris Clarke:  You have to look at a map to know whether you're on the reservation or not. When I lived in Palm Springs, there was a diner half a block up from my apartment that I used to like to go to for breakfast, and walking the three minutes from my apartment to that diner involved walking onto the Agua Caliente Reservation and then eating and then walking back off the reservation.

[00: 05: 26] Chris Clarke:  A lot of lines on maps in the desert reflect that railroad land grant era. Other lines follow geographical features. Rivers are often boundaries, not just for nations and states and counties, but also for wilderness areas and national monuments and other designations. Sometimes the shapes on the map follow watershed boundaries.

[00: 05: 48] Chris Clarke: On one side of the line, rain drains into river A, and on the other side of the line, it drains into dry lake B and evaporates. Sometimes the lines on the map are hard to figure out unless you know what went on during the process of designating whatever it is that's being mapped. Establishing a city or a wilderness or a park, a change in boundary of two miles might be the result of a bitter political argument, sometimes a lawsuit, campaigns for and against.

[00: 06: 20] Chris Clarke: In other words, most maps reflect human thought and human history as much as they do accuracy to what's on the ground, and I find that just fascinating. Other maps tell stories that have nothing to do with human activity except for the act of mapping, and topo maps and geological maps are an example. A geological map can tell a story about how the landscape was formed, where it was submerged under a shallow sea, or where it was part of a mountain that got worn down, or where the sediment from that mountain got compressed into new rock. A map of the Grand Canyon is a map of probably five million years of erosion.

[00: 07: 02] Chris Clarke: The maps I want to talk about today are range maps, those color-coded charts that show the estimated range of a species or some other group of living things. You see them in field guides and scholarly papers. For example, I talk about Joshua trees a lot, as regular listeners know, and range maps of the Joshua tree are becoming more and more precise.

[00: 07: 27] Chris Clarke:  Between Google Earth and fast computers, we can pretty much put a map together that shows the location of every single Joshua tree across the four states where it's native, and there are cartographers and biologists working on that as we speak. But the story those maps tell, especially now that the Joshua tree is generally thought to consist of two closely related species, is a story of migration and separation and reunion.

[00: 07: 55] Chris Clarke: Joshua trees headed north as the desert warmed after the Ice Age. Some went northwest, others more to the northeast, and those western and eastern populations of Joshua trees diverged into two distinct species. In the Tikaboo Valley north of Las Vegas, the two species of Joshua trees meet up well to the north of most of the populations of either species.

[00: 08: 20] Chris Clarke:  This is an epic story covering tens of thousands of years and is also likely related to the carving of the Grand Canyon. You wanna hear more about that, let me know. Now, with range maps, many people take them as kind of immutable, as representing what is supposed to be, and that kinda misses the point. Like any other map, the range map is a snapshot.

[00: 08: 46] Chris Clarke:  It's a snapshot of what we know about where that particular kind of organism is at the time the map was drawn. Often enough, you'll see range maps that show the current range of a species superimposed on the historic range of the species. In many cases, that historic range is from the 1850s or something similarly far back.

[00: 09: 07] Chris Clarke:  And those maps are often quite useful, and they have an important purpose. They tell a story explicitly of how a species' range has changed, generally due to the advent of European settlement. But even that historic range on the map is often taken to mean where that species is supposed to be, which is a useful tool if you're campaigning to protect or restore a species' habitat.

[00: 09: 32] Chris Clarke:  And if that's what you're doing, more power to you. But sometimes it just leads to misunderstandings. Around 20 years ago, I saw my first free-flying California condors on the South Rim of the Grand Canyon, right at Grand Canyon Village. I was thrilled. The visit was amazing. It was a hike down to the river and back out over the course of four days, and then I went back to the Bay Area and shared my experience and talked about how excited I was to finally see California condors flying free.

[00: 10: 05] Chris Clarke:  And I shared that with someone I worked with at the time who knew something about condors, and he was appreciative of how cool it was to see them. But he also kind of sneered and said, "Yeah, the Peregrine Fund transplanted them there, but they aren't even in the historic range." I didn't argue, but I did wonder quietly which historic range he meant.

[00: 10: 28] Chris Clarke: California condor fossils have been found across North America. The Grand Canyon is absolutely within the condor's historic range, depending on what you define as history. Anyway, if we had the luxury of being able to predict the future and technology that allowed us to print maps that were not only accurate in the spatial dimensions, but also in the time dimension, a range map of a species would look like a spot right where the species arose however many million years in the past.

[00: 11: 01] Chris Clarke: That spot would develop into weird blobby geometrical shapes that sometimes expanded, sometimes contracted, sometimes split into two or more distinct groups. Sometimes those groups merged again. I imagine it like a lava lamp, basically blobs moving around, changing shape. The Joshua tree blob is split into two and those two blobs are just kissing in theTikaboo Valley.

[00: 11: 31] Chris Clarke: There's a genus of ground squirrel called Xerospermophilus, from the Greek xero, meaning dry, X-E-R-O, and spermophilus, meaning seed lover. There are four species of Xerospermophilus in North America. Two of them, the spotted ground squirrel and the Perote ground squirrel, are not particularly relevant to the story.

[00: 11: 56] Chris Clarke: The other two species are the round-tailed ground squirrel and the Mohave ground squirrel. Now, the round-tailed ground squirrel ranges from around Ciudad Obregón in southern Sonora and the easternmost parts of Baja California, and it stretches as far north as Clark County, Nevada. East to west, it ranges from around the Chiricahuas in southeastern Arizona over to the central Mojave near Barstow. And to the casual onlooker, the Mohave ground squirrel is essentially the same as the round-tailed ground squirrel.

[00: 12: 28] Chris Clarke: It's a little bit pinker in the underbelly. The Mohave ground squirrel lives in the western Mojave Desert, and it ranges from the northern foothills of the San Gabriel Mountains in L.A. County up to the southern shores of Owens Lake, and then eastward to the middle of Fort Irwin, just north of Barstow. It has one of the smallest ranges of any squirrel in North America, and that range is getting smaller as we develop its habitat into farms and solar fields and abortive attempts at suburbs.

[00: 12: 58] Chris Clarke: The Mohave ground squirrel's range is getting small enough that California has listed it as a threatened species under the California version of the Endangered Species Act. The ranges of the round-tailed ground squirrel and the Mohave ground squirrel overlap very, very slightly.The cool thing about Mohave ground squirrels and round-tailed ground squirrels is that they're so similar that when they live within mating distance of each other, like in the overlap, they can create offspring that are sometimes fertile, unlike a lot of cross-species hybrids.

[00: 13: 30] Chris Clarke:  They can reproduce, which means that they're very closely related species. And yet, despite their interfertility, to the extent that they are interfertile, they have maintained their status as separate populations even though their ranges overlap. If they can successfully interbreed and produce the occasional fertile offspring, you would think that over the course of millions of years, those two populations would just merge.

[00: 13: 57] Chris Clarke:  How did they not? What's keeping them mostly apart? As is the case when many species split into two distinct species, the answer involves a barrier. But this isn't a barrier that exists now. It's a former barrier that has left traces that scientists can read easily, the rest of us might not notice.

[00: 14: 21] Chris Clarke:  Something in the Mojave Desert, maybe even before the Mojave Desert was really a desert, but something here kept those two populations of ground squirrels apart, kept them separated, kept them geographically isolated. And we'll talk about what that was after the break.

[00: 14: 47] Joe Geoffrey: Don't go away. We'll be right back.

[00: 14: 51] Chris Clarke: For this week's offering by Nature Sounds recordist Fred Bell, we have Red Rock Canyon National Conservation Area. Fred writes, "The dawn chorus at Red Rock Canyon National Conservation Area out of Las Vegas. Oak Creek is a popular hike with Las Vegas locals." Let's listen.

[00: 16: 24] Joe Geoffrey: You're listening to 90 Miles from Needles, the Desert Protection Podcast. Water may feel heavy in your pack, but it's nothing compared to carrying you out of the desert.

[00: 16: 39] Chris Clarke: Before the break, we were talking about what kept these two populations of squirrels, the Mohave ground squirrel and the round-tailed ground squirrel, separated long enough to diverge into distinct species.

[00: 16: 50] Chris Clarke:  It's confusing, 'cause there seems to be nothing in the way, nothing in between these two species that would keep them from meeting up and falling in love and raising a family. And some of the offspring would actually be able to reproduce on their own, and this would muck up the neat boundary between those species.

[00: 17: 08] Chris Clarke: And that's actually happening right now in a couple of limited locations around Hinkley and then around Helendale in California. Why isn’t it happening throughout the range of both species? Well, the answer requires us to go back a little bit. The San Bernardino Mountains and the San Gabriel Mountains, which form the southern border of the West Mojave Desert, have been rising for millions of years because of pressure from the Pacific Plate pushing against the North American Plate as Los Angeles slowly slides toward Alaska.

[00: 17: 43] Chris Clarke: And the mountains are still rising to this day. Around one and a half million years ago, there was a river that had been draining the young mountains around what's now Big Bear, flowing into the Pacific Ocean. But as the San Bernardino Mountains rose, they got tall enough that the river kinda got nudged to the north.

[00: 18: 05] Chris Clarke:  It couldn't flow to the Pacific anymore, so it started flowing northward, at first into a basin that is now occupied by the city of Victorville. A lake formed there, grew and dwindled over centuries based on shifts in the climate and shifts in the amount of precipitation falling on the mountains. There were wetlands and lakes there in the basin.

[00: 18: 27] Chris Clarke:  Eventually, that river filled the Victorville basin with sediment, and then a little bit less than 600,000 years ago, the Victorville basin had collected too much sediment from the river to hold all the water the river was providing. It overflowed. It breached a threshold, and the river, the Proto-Mojave River, began to flow northward across the desert, eventually reaching a couple of basins west of Barstow.

[00: 18: 58] Chris Clarke: New lakes formed there. One of them is these days a popular spot for birders, the usually dry playa called Harper Lake. Those lakes filled and receded and filled and receded, and then about half a million years ago, they overflowed, and the spillage flowed eastward and filled a basin we now call Lake Manix, which was just east of Barstow. At its broadest and deepest, Lake Manix approached 200 feet deep in some places.

[00: 19: 31] Chris Clarke: It wasn't a neatly defined lake. There were lobes of it that pointed up into adjacent valleys and then retreated. And here's where we run up against that map as snapshot issue again. It's easy to find maps online showing the outlines of Lake Manix, and indeed of all the vanished lakes that once dotted the Mojave.

[00: 19: 51] Chris Clarke: They seem well-defined and well-marked out, but in reality, those colored map splotches shifted and advanced and withdrew like an amoeba under a microscope. Lake Manix expanded and contracted, and the Mojave River feeding it shifted back and forth. Sometimes it abandoned Lake Manix altogether and headed back to Lake Harper.

[00: 20: 14] Chris Clarke: That whole section of the ancient Mojave was a string of wetlands stretching from the mountains near the Victorville Basin to around the area of Boron, then eastward through where Barstow is today, and then northeastward. The last time Lake Manix experienced its highest stand, which means its highest water level, was just before Lake Manix overflowed, carving Afton Canyon.

[00: 20: 39] Chris Clarke: And as Afton Canyon deepened, it drained Lake Manix. By 20,000 years ago, the Mojave River just passed by the old drained Lake Manix and flowed through Afton Canyon, creating a new lake in the general vicinity of Baker, California, which we now call Lake Mojave. And part of Lake Mojave still arises every now and then in a wet year.

[00: 21: 02] Chris Clarke:  The water level is often just a couple inches below the surface. And people who have tried to drive the Mojave Road in certain kinds of weather find that out to their intense chagrin. Anyway, you get the picture. For a long time, where we today see badlands and dunes and seemingly endless expanses of creosote, there were grasslands and open park-like savannas of juniper trees, wetlands and lakes, and shifting braided rivers fringed with tules and sedges and desert willows and true willows.

[00: 21: 35] Chris Clarke:  And at this point, you might be assuming that I'm going to tell you it was the Mojave River drainage complex of wetlands and lakes and shifting braided rivers that separated the squirrels into two distinct populations, and that it was because of this separation that they evolved into two distinct species.

[00: 21: 53] Chris Clarke:  And truth be told, if we were talking about this 15 years ago, that's exactly what I would have told you. It was a commonly accepted hypothesis. But a mitochondrial DNA study of the two species in 2010 indicates that they actually diverged quite a long time before the river separated them, maybe as much as 4 million years ago.

[00: 22: 18] Chris Clarke:  In that earlier time, the squirrels weren't separated by water. They were separated by its absence. The same basins that the Mojave River filled to create Lakes Harper and Hinkley were forbiddingly arid, at least too arid to support squirrel habitat. And those arid basins separated the squirrel population long enough to allow it to diverge into two species.

[00: 22: 40] Chris Clarke: And this was long before the Mojave River really existed. But when the river was there, there was really good squirrel habitat on both sides of the river. And that river and its lakes and wetlands kept the squirrel populations on either side from crossing. But then the rain ceased. The San Gabriel and San Bernardino Mountains had risen to truly lofty heights and created a rain shadow that kept moisture from the Pacific from reaching the desert.

[00: 23: 13] Chris Clarke:  The Mojave became the hyper-arid place that it is today. And by eight thousand years ago, there was no barrier between the squirrel populations anymore. These days, the Mojave does run on the surface through Victorville Narrows and Afton Canyon, but on most of the river, most of the time, it flows underground.

[00: 23: 33] Chris Clarke: And an underground river is no obstacle to a determined squirrel. For the last eight thousand years, the squirrels have been free to intermingle. It's just taken them a while to meet up. Now this is a pretty hypothesis, but seems like there's no way we could check it. I mean, how do you go 8,000 years back and study the behavior of the ancestors of today's squirrels?

[00: 23: 58] Chris Clarke: It turns out we do have some evidence. It's been calculated that if either of these squirrel species is confronted with suitable habitat that they aren't yet occupying, and if they're thriving well enough that they have extra squirrels that can go set up new homes in this new territory, the movement of that range front, in other words, the movement of the edge of that colored blotch in our hypothetical self-updating range map, moves no more than five meters a year, a little bit less than 17 feet. Now, right now, there are populations of each species on the wrong side, so to speak, of the Mojave River.

[00: 24: 40] Chris Clarke: There are a few Mohave ground squirrels south and east of the Mojave, and a few round-tailed ground squirrels north and west of the Mojave. But none of those advanced populations, I guess we could call them, are more than thirty kilometers away from the river. Thirty kilometers is thirty thousand meters. The range of either species only expands at five meters per year.

[00: 25: 06] Chris Clarke: Thirty thousand divided by five is six thousand.

[00: 25: 10] Chris Clarke: And 6,000 years ago was after the river dried up. This isn't a slam-dunk proof of the idea that the river was keeping the squirrels apart, but it is compatible with it, especially when you consider that squirrels may not have made the full five meters a year all the time, depending on climate.

[00: 25: 30] Chris Clarke: If I was to recast this story in sort of mythical terms, it would go like this. There was once a squirrel people, ancestral to both the Mohave ground squirrel and the round-tailed ground squirrel, living seven or eight million years ago in a broad fertile plain, spending their lives digging holes and eating those seeds that their genus name says they love, making new squirrel generations and trying not to get stepped on by saber-toothed cats and ground sloths and camels.

[00: 26: 02] Chris Clarke: And as the climate dried, this squirrel people found itself split in two on either side of the forbiddingly arid area in the western Mojave. Stayed that way for millions of years. And then that aridity lessened, the climate got cooler and wetter, and the overflow of mountain streams into a chain of lakes and wetlands and lagoons and oxbows from the base of the San Bernardinos in the Mojave Desert all the way up to where the city of Baker would later be kept the squirrels from each other. It was an impassable barrier. Now I'm anthropomorphizing here clearly, so forgive me. But I like to imagine the different populations of squirrels that had by now evolved into two distinct species looking at each other wistfully from across the water.

[00: 27: 00] Chris Clarke:  And then 8,000 years ago, more or less, that obstacle went away, and we are now watching the slow reunion of these two species. Are they gonna interbreed and muddy the boundary between the two species? Are they gonna prove to hate each other and defend their territories? Is climate change gonna force them to move north in different directions and remove their zone of overlap?

[00: 27: 25] Chris Clarke:  Are they gonna do something else entirely that we can't anticipate? Just like a cliffhanger in the final episode of a TV season, this story is to be continued. Whatever sentient species is making range maps in 50,000 years, and personally, I'm betting on the descendants of today's ravens, that species is going to make a round-tailed ground squirrel range map that looks very, very different from the one we have now.

[00: 27: 53] Chris Clarke: Probably not reaching nearly as far south as it does and stretching northward up into Utah or even Colorado. And with any luck, there will still be a splotch in that range map representing the Mohave ground squirrel, which is, as I said, threatened under the California Endangered Species Act. If this story has a moral, it's simply this:  it would be a shame to watch that Mohave ground squirrel splotch wink out in a haze of apathetic resource extraction and heedless development, which is, after all, what's threatening the Mohave ground squirrel to begin with.

[00: 29: 00] Chris Clarke:  Thanks for sticking with us through this story. I hope you enjoyed it. I wanna again thank Cheryl Cox for joining our donors. You can go to 90milesfromneedles.com/donate in order to do that. I'm also very, very stoked to announce that we are officially soliciting submissions of applications for our fellowship for desert reporting.

[00: 29: 22] Chris Clarke: If you are interested in putting together a little bit of reporting for us and making a slightly larger amount of money than I've been paid for freelance writing or editing in the last little bit, somewhere in the neighborhood of 1,250 bucks on average, you can go to our fellowship application page at thedamn.org, T-H-E-D-A-M-N.O-R-G/fellowship-application,

[00: 29: 51] Chris Clarke: T-H-E-D-A-M-N.O-R-G/fellowship-application.Thedamn.org is the website of the Desert Advocacy Media Network. We're really looking to expand our range of voices and our range of coverage, and I think you're gonna find it worthwhile to listen to and hopefully worthwhile to apply yourself. We don't necessarily insist on contributions of fellows being audio reporting.

[00: 30: 20] Chris Clarke:  We're open to other ideas, story maps or articles for our website, social media-based reporting. We're open to a bunch of different ideas. And just as a reminder, you don't need to be a working journalist to apply. You don't need to have a journalism school degree. We are looking for enthusiastic people who want to learn, who want to protect the desert, and who wanna share information about the desert, whether that's following a political development or talking about a part of the desert that people don't know well enough, cultural issues, environmental justice issues, border issues, tribal issues, natural history, birding, geology, whatever.

[00: 31: 01] Chris Clarke:  If you wanna put something together about it and you want some expert help from experienced journalists and editors, please consider applying. If you don't fit that bill but you know somebody that does, please share. And we appreciate you very much. It has cooled off just a little bit in the desert where I am.

[00: 31: 21] Chris Clarke:  We finally got a little bit of rain falling on the roof of the studio here, possibly as much as a tenth of an inch. We have an embarrassment of riches when it comes to precip here in Twentynine Palms. I am going through a routine medical procedure early next week that will lose me as much as two days of work, so it's anyone's guess as to whether or not there's gonna be an episode next week, but I'll do my best.

[00: 31: 49] Chris Clarke: And in the meantime, I will see you at the next watering hole.

[00: 31: 54] Joe Geoffrey: And that brings us to the end of this episode of 90 Miles from Needles, the Desert Protection Podcast. You can find show notes for this episode along with links

[00: 32: 08] Joe Geoffrey: and background at ninetymilesfromneedles.com. We're also on social media. You can find us on Facebook, Instagram, Bluesky, and Threads. Just search for 90 Miles from Needles. And if you'd like a more direct line, you can reach us on Signal at hey90mfn.67.

[00: 32: 29] Joe Geoffrey: If you'd like to support the show, you can make a donation of whatever size and frequency feels right to you at ninetymilesfromneedles.com/donate. Listener support is what makes this podcast possible. Our voiceover is by Joe Geoffrey. Podcast artwork is by Martín Mancha. Nature sounds are recorded by Fred Bell.

[00: 32: 52] Joe Geoffrey:  Our theme song, Moody Western, is by Brightside Studio with additional music licensed from independent artists.

[00: 33: 02] Chris Clarke:  Other music in this episode is by DS Pro Music, Hyperprod, Oleksandr Ignatov, and Sound the Limit.

[00: 34: 00] Joe Geoffrey: 90 Miles from Needles is a production of the Desert Advocacy Media Network.