An "Extinct" Fish Finds Life Again in a Parched Desert: The Saga of the Shoshone Pupfish

The pupfish habitat at the springs in Shoshone, east of Death Valley National Park

Of all the things one might look for while exploring intense desert environments, what is the most unlikely form of life you would expect to encounter? Fish of course. It's practically an oxymoron to use the term "desert fish". But in the harsh desert environments of eastern California and western Nevada, there are indeed fish. And not just a single species, but around a dozen species and subspecies. There are nine distinct populations of the Cyprinodon Pupfish, three species of Speckled Dace, and a Poolfish. How they survive today, and how they got there in the first place is a fascinating story.

How they survive is not difficult to understand: despite the aridity of the California desert, there are sources of water. There are permanent springs and pools of water scattered all around Death Valley and the Amargosa River Basin, and the fish have adapted to life in waters that might be hot, cold, fresh, or salty.

How they got there in the first place is a little trickier to understand. Our climate has been subject to huge variations over the last two million years, and more than a dozen times, it got much cooler and glaciers developed and expanded, especially in the Sierra Nevada mountains. Some of the meltwater from those glaciers flowed into the deserts of the Basin and Range province and accumulated in huge freshwater lakes. As a lake basin filled (such as at Mono or Owens Lake), it spilled over into the next lake basin until a network of lakes extended from the Sierra Nevada to Death Valley. The Amargosa River flowed through western Nevada, also ending in Death Valley. So there was plenty of water once upon a time.

At some point in time, a connection was made with the Colorado River, and fish were able to make their way into the network of freshwater lakes, and they thrived. But as each glacial stage ended, the lakes would begin drying up and most of the fish lost their habitat and went extinct. But those very few species that could adapt quickly enough took refuge in the rare and isolated springs and pools. A few, including the Lahontan Cutthroat Trout survived in the cold streams, lakes and rivers of the eastern Sierra Nevada. Those trapped in saline waters had to adapt to the salty conditions. Some fish adapted to high temperatures,  and unlike pretty much any other fish in the world can survive in water that reaches a hundred degrees or more.

One of my very few photos of the Devils Hole Pupfish, taken from around 100 feet away.

Perhaps the most famous of these fish is the Devils Hole Pupfish (above), found in a single cavern opening in the Ash Meadows National Wildlife Refuge (the spring officially lies in an outlier of Death Valley National Park). Their story is compelling, but they are not the fish I'm discussing today. You can read about them if you wish here or here.

 

The various populations of pupfish survived for thousands of years in isolation from human developments. But the colonization and occupation of the desert by miners and ranchers spelled doom for some of them. One species, the Tecopa Pupfish, was driven extinct pretty much in an afternoon when pipes were installed at the one spring where they lived. A similar fate apparently happened to a different subspecies, the Shoshone Pupfish (Cyprinodon nevadensis shoshone) in the 1960s as springs in that area were developed for domestic use at the village of Shoshone. The species was declared extinct in 1969, as none could be found anywhere.

Improbably, a small population of the fish actually survived the devastation of their original habitat by taking refuge in a nearby irrigation ditch, unnoticed by anyone. In 1986 they were rediscovered, and a cooperative effort by the private landowner and several environmental organizations resulted in a resurrected habitat. This habitat was actually expanded to three pools and some artificial off-site refuges as well. Despite visiting Shoshone yearly for the last three decades, I never heard about the efforts being made on behalf of the fish's well-being. 

That changed last week when I found out that a nature trail had been constructed, and interpretive signs posted that allowed for some close viewing of the diminutive fish (as well as another highly endangered creature, the Amargosa Vole). The site also serves as an excellent habitat for a large variety of birds, and we saw Western Bluebirds, Yellow-rumped Warblers, White-crowned Sparrows, a Costa's Hummingbird (a life-lister for me) and we could hear Verdins chattering away in the brush.

The trail is just off the main highway in Shoshone, and the locals seem proud of the efforts and can easily point the way to the trailhead, next to the local school. If you ever travel to Death Valley from the east, you can't miss the town. It's the only gas station and food stop for many miles. Don't forget to stop in at the local museum for a look at the Columbia Mammoth fossils on display inside!

 

The Hawai'i That Was: A Tale of Two Kipukas, and Thoughts on the Rarest Plants in the World

Thousands of years ago there was an eruption at Humu'ula Saddle, the broad wide pass between Mauna Loa and Mauna Kea on the Big Island of Hawai'i. The eruption was mildly explosive, so the resulting landform took shape as a cinder cone. At the time, it was a barren peak amidst a forest of native Koa trees. As time went on, soils developed on the cinder cone, and the forest expanded to cover the hill. Much later the situation was reversed because extensive sheets of basalt flowed from Mauna Loa, most recently in 1843 and 1935. They covered the entire saddle area and decimated the Koa forest. Except for the lone cinder cone. A small remnant of the ancient forest survived.

The hill, called Pu'u Huluhulu ("hairy" or "furry" hill) is a stark example of a kipuka, an island of sorts in the middle of lava flows that preserves a portion of the original pre-flow surface and the plants and animals that lived there. The Google image above shows just how isolated the cinder cone is. If you are looking for the "Hawai'i That Was", a kipuka is a good place to start. They are like museums of what once was, but they are far more than that. In preserving the flora and fauna, they provide the genetic material that will eventually repopulate the areas of devastation.

Edge of Pu'u Huluhulu, where plants start to recolonize the lava flows.

There are hundreds of kipukas spread across the Big Island on Mauna Loa and Kilauea. We explored two of them on our recent exploration of the islands: Pu'u Huluhulu at Saddle Road, and Kipuka Puaulu in Hawai'i Volcanoes National Park.  Because it is a hill at the boundary between Hawaii's two largest volcanoes, Pu'u Huluhulu offers dramatic views. It is also a bit schizophrenic: it is composed of cinders from the "plumbing" system of Mauna Kea, but was later intruded by dikes of basalt from Mauna Loa.

Mauna Kea from the top of Pu'u Huluhulu

The forest of Pu'u Huluhulu may have escaped the destruction of lava flows, but it has not escaped alteration by humans. The northwest flank was quarried for cinders in the past, and is still barren on that side (although geologists appreciate the exposure of dikes and cinder layers). Cattle, goats and sheep have grazed the hill at various times, although a fence now keeps them out (as long as hikers close the gates). Several short trails, though steep and rocky in a few spots, provide access to much of the kipuka, and the site is recognized as a hot spot for viewing rare native birds.

Kipuka Puaulu, the "Bird Kipuka", at Hawai'i Volcanoes National Park (forested area in center of picture).

At Kipuka Puaulu (or Kipukapuaulu) in Hawaiian Volcanoes National Park the situation is a bit different. For one, it is about ten times larger than Pu'u Huluhulu, covering about a square mile. It's also more of a depression than a hill. About 600 years ago, a lava flow from Mauna Loa overwhelmed the forest of mature Koa and Ohi'a trees, but left a fragment of the woodland sitting on 8,600 year old lava unscathed. Over the years the kipuka was occasionally mantled with ash from the eruptions of nearby Kilauea, but the forest persisted, in part because the ash produced thick moist soils. Today, the kipuka contains one of the most diverse collections of native flora on the Big Island. A beautiful and serene one-mile trail winds through the unique preserve. A Hawaiian elder calls it a "Residence of Godly Existences".

It wouldn't be quite correct to describe Kipukapuaulu as an untouched pristine environment. Cattle were released on the islands in the late 1700's, and pigs and goats moved in as well. The natural flora of the kipuka had no defenses against the aggressive grazers, and by the early 1900's, the kipuka was a park-like grassland shaded only by the "grandfather trees", the older Koa and Ohi'a trees that the cattle couldn't reach. A park sounds pleasant enough, but the trees couldn't reproduce (the saplings were quickly eaten), and the diverse understory of shrubs and perennials had been replaced by alien grasses (below).

Source: National Park Service (https://www.nps.gov/havo/planyourvisit/upload/Kipukapuaulu_Trail_Guide.pdf)

The potential value of the kipuka as a preserve of rare native species was recognized surprisingly early by botanists, who arranged for the removal of cattle in 1928, and the removal of goats and pigs by 1968 (a fence surrounds the kipuka). Volunteers removed the worst of the invasive weeds and grasses, and seeds of native plants lying dormant in the soils started sprouting. In other cases the native species were planted by hand. After a few decades, the kipuka is returning to a condition that is at least comparable to its natural primeval state.

Hau kuahiwi (Hibiscadelphus giffardianus), once extinct except for a few seeds

Have you ever wondered about the identity of the rarest plant in the world? We recently had a story about a single plant of Franciscan Manzanita in San Francisco, discovered at an intersection that was being repaved. How about a plant with no living shoots or branches? One of the strangest stories I've run across regarding Kipukapuaulu is that of the small Hibiscus tree called Hau Kuahiwi (Hibiscadelphus giffardianus). A botanist named Joseph Rock (with that name he should have been a geologist) discovered the sole remaining specimen of the plant on planet Earth in Kipukapuaulu in 1911 (the cows had not quite finished it off). The one plant died in 1930, but a local resident managed to collect enough seeds to get a few sprouts going, and so the plant survives in captivity, so to speak. Around 200 have been planted in the kipuka that was its ancestral home (as well as the adjacent kipuka, for insurance from possible future lava flows).

The kipuka came under protection pretty much in the nick of time. Some of the "grandfather trees" that shade the preserve have been dying off in recent years (like the trees in the picture above). On species, the Ohi'a tree (Metrosideros polymorpha) is one of the most extraordinary of the native trees in Hawai'i. The Ohi'a thrives in a greater range of environments than pretty much any tree on the planet, being found in places as diverse as new lava flows, desert slopes, and alpine ridges. They can appear as small shrubs or as huge rainforest canopy trees nearly a hundred feet tall. The Ohi'a trees in the kipuka are dying, perhaps of old age, a newly spreading fungal disease, or because of a series of droughts in recent years (maybe all three). With the diversity of plants now in place, one would hope the kipuka would be able to adapt to the loss of the old trees.

 A few steps off the trail is an intriguing opening in the ground. It is a lava tube, part of the plumbing system of basaltic lava flows. Because it has existed for more than 8,000 years, it is one of relatively few that has some species of cave-dwelling organisms (including the first one discovered in Hawaii). Like the rest of the kipuka, the cave was heavily impacted (in this case by graffiti artists, vandalism and trash), but visitors are now encouraged to leave the cave alone.

The preponderance of native plant species attracts the native bird species to the kipuka, and they can commonly be seen flitting about in the forest canopy. They thrive here for two reasons: at 4,000 feet, they are above the mosquito zone, so are protected from transmitted diseases, and mongooses have not crossed the barren lava flows to prey on the birds. They are frustratingly difficult to photograph, and I am actually cheating here by showing a picture of an Apapane from nearby at the park visitor center.

The bird below is often seen in Kipukapuaulu, but it is not actually a native. It is a Kalij Pheasant, a 1962 import from southern Asia. There is some concern about the effects they might be having on the vegetation.

To the average visitor the islands, the kipukas are a little-known aspect of Hawaiian geology and biology, but they are an important link to the past, and an important repository of the island's genetic history. If you ever visit, set aside some time for an exploration.

View from the forest on Pu'u Huluhulu towards extensive Mauna Loa lava flows.

Much of my information in this post is drawn from the Kipukapuaulu Trail Guide, written by Tim Tunison and Andrea Kaawaloa-Okita, and published by the Hawai'i Natural History Association. Additional information was gleaned from the book Hawai'is Native Plants by Dr. Bruce Bohm.

This is One of the Rarest Forests on our Planet, and Yet One of the Most Widespread

This is one of the rarest forests on our planet. I know of a number of different species that are represented by extremely limited habitats; there are the Dawn Redwoods of China (a grove of maybe 5,000 individuals), the Wollemia "Pine" of Australia (only a 100 or so in the wild), and the Ginkgo biloba (a few scattered possibly wild groves). But I also have a rare native tree in my own backyard, one that is found in just five widely scattered groves: on Cedros and Guadalupe Islands offshore of Baja Mexico, and in Cambria and Ano Nuevo along the California Coast. The fifth, the one I visited this last weekend, is here on the Monterey Peninsula, south of San Francisco.

Natural distribution of the Monterey Pine (http://evolution.berkeley.edu/evolibrary/article/montereypines_01)

The species is, strangely enough, the Monterey Pine (Pinus radiata). The pine is well known to many as a Christmas tree species or as a landscaping ornamental, and it is grown as a lumber species on some 10 million acres worldwide, mainly in Australia, New Zealand, Spain, South Africa, and Chile. It's a common tree. And also practically unrecognizable in its own native habitat. The trees that are grown for timber, landscaping and Christmas are highly modified organisms in the genetic sense (GMOs). They look little like the spindly knotted trees that grow on their native landscape.

We may often prefer to choose "organic" or "natural" foods for our diet, but practically none of the foods that we grow for our consumption look much like their wild forbears. Bananas, for instance, were practically inedible with giant seeds. Corn was little more than a grass, as was wheat. But these practically inedible natural species have a great value to our civilization: genetic diversity.

Our food supply is vulnerable to disruption from any number of diseases and disorders: such things as fungi, bacteria or viruses could kill off vast sectors of our agricultural products because they are genetically homogeneous. The currently favored banana variety, for instance, may be wiped out in just a few years by a  fungus. 

And so it is with the Monterey Pine. Silvicultural methods have taken the pine and transformed it into a rapidly growing tree with few knots in the lower two-thirds of the tree. But the pines that grow on plantations across the world do not have the genetic diversity of the forests in the isolated stands in California and the Baja islands.

The native groves of Monterey Pine are under environmental assault, from development pressures, and from disease. The Pitch Canker fungus weakens the trees, making them susceptible to beetle attack. There is not much in the way of a coordinated treatment for the trees. None of the native groves are on protected federal land, and only one grove is within a state park. For the most part the native groves exist at the pleasure of the private corporations that own the land.  

Although they have been far too willing to cut down Monterey Pine forests to make villas and golf courses, the corporation that owns the forests in these pictures knows it has some fiscal responsibility to its shareholders to preserve some intact forests of these trees. They make a lot of money charging tourists like myself who pay $10 to follow Seventeen Mile Drive to see the forests along with the beautiful coastline, the wildflowers, and the mansions of the rich inhabitants of the area. 

Strangely enough, the Monterey Peninsula plays hosts to more than one extremely rare native forest. The Monterey Cypress (Hesperocyparis macrocarpa) is found in natural groves only at Cypress Point on the peninsula, and at Point Lobos State Reserve. The trademarked tree called the "Lone Cypress" is perhaps the most famous single tree in the California (I think the sadly deceased Jeffrey Pine on the summit of Sentinel Dome in California was a close competitor for the honor). Like the pine, it has become widespread due to planting as an ornamental.

For more on the evolution and distribution of the Monterey Pine, see http://evolution.berkeley.edu/evolibrary/article/montereypines_01.

Sea Otter using Geologic Materials to Procure a Snack

If I lived along the coast, I would get to see this kind of thing all the time, but I don't, and I don't always see otters when I do visit, so this was kind of special. The funny part is, I didn't really notice the otter at the bottom of the scene pounding on the rock until the very end when I zoomed in. We spent part of the afternoon at Cypress Point on the Monterey Peninsula, and were so distracted by the Harbor Seals that we nearly missed seeing the otters a little ways offshore.

I mean, really, would you be distracted by this?

I remember reading as a kid how humans were better than all the animals because we used tools. I also remember those first discoveries by Jane Goodall and others that primates were using tools, and later how otters used rocks to bust up shells. The otters will carry a rock in a pouch under their arm, and scour the seafloor for snails and other delectable shellfish, bringing them to the surface for a geology-based extraction leading to a juicy snack.

But I never got to witness such things in all these years. I didn't get any clear pictures of the otters today other than the video, so I dug into the archives for a few pictures of otters in Morro Bay that I photographed in 2007.

California's Sea Otters are an endangered species, and it is practically a miracle that we have any at all. Their original population was estimated to be around 16,000, but Russian fur traders and others extirpated most of the colonies. They were thought to be extinct until 1938, when a group of about 50 were discovered in a living in a cove near Bixby Bridge north of Big Sur. Their numbers have risen slowly to about 3,000 individuals today. It's hard to imagine that we nearly lost them forever.

A Bird Shangri-La No More: The Moas of New Zealand

Blogging always involves a little bit of free association, where inspiration comes from numerous unrelated events over the course of a few days. I've started my fall semester, and I've met 170 new people over the last week. I've given introductory presentations that describe the reasons a person might want to pursue studies in geology and the earth sciences including a rundown of some of the interesting fossils that have been found in the region. So, I've been thinking about the past, the very deep past of millions of years ago.

Then, I've been blogging over at Geotripper's California Birds about some birding adventures overseas including trips in Switzerland, Italy, and Australia. While looking for bird pics, I came across the picture below of some Moa replicas that we saw at a New Zealand wildlife park. Replicas, because Moas no longer exist in our world. But once there was a Shangri-La for the birds, a paradise on Earth, in New Zealand.

12 foot fiberglass Moas lurking in a Gondwana forest in New Zealand

New Zealand was a paradise for birds because the island mass separated from other continents prior to the mass extinctions of the late Cretaceous. Small mammals were present, but on the islands they were never much of a threat to the birds, and eventually they went extinct, except for some bat species. With the loss of the dinosaurs and the mammals, the only vertebrates in position to dominate the terrestrial ecosystems were the, uh, dinosaurs. The avian dinosaurs. With no reptilian or mammalian predators, the birds were able to evolve a flightless lifestyle (flight is an expensive energy proposition if it is not necessary for survival). Eventually a number of very large birds evolved, including eleven species of Moas. The largest stood over 12 feet tall (3.6 meters). The Moas were mainly plant-eaters but predators existed on the islands as well, including the extremely large Haast's Eagle (Harpagornis moorei) with a wingspan of nearly 10 feet (3.3 meters).

The Moas in the picture above aren't real. I've added a shot of an Emu from the wildlife park we visited as a stand-in for the large, flightless birds

The trees on the island provide another link to the past. Some of the huge tree ferns in New Zealand evoke Jurassic forests of the long-sundered Gondwana supercontinent. The ferns in the photo below line the opening of a 75-foot deep explosion pit at Orakei Korako Geothermal Area on the North Island. I've never such huge ferns before.

The ancient tree that captured my imagination the most was the Kauri tree (below), one of the bulkiest trees on the planet, rivaling even the Sequoia trees in my own backyard of the Sierra Nevada. The most mature trees are not quite 200 feet high, but their trunks remain thick practically to the crown. Their history extends back into Jurassic time. They once covered large portions of the islands, but unfortunately their wood is strong, mostly knot-free, and attractive. Something like 95% of the original forests have been cut down, and old-growth forests are exceedingly rare and precious. The trees are now protected by law, but ironically, dead trees in swamps are not, and the wood is durable enough that some of the trees from the swamps are still utilized legally, despite having been dead for hundreds or thousands of years.

Unfortunately, the arrival of humans on the islands around 700 years ago spelled doom for the avain Shangri-La. Slow-moving, with no defensive instincts, they were hunted to extinction in just a few decades after the human invasion. When they were gone the large raptors lost their primary food source and went extinct as well. Of the flightless birds, only a few species of the Kiwi, the threatened small forest dwelling bird, survives today.

A New Zealand Fan-tail, one of dozens of endemic bird species found in Kiwi land

Geology and paleontology are disciplines for creative and imaginative people. They recreate for us past worlds full of strange and wondrous creatures that are long gone from today's world. There are enough samples of DNA from the extinct Moas that there is a slight hope of bringing them back as living species, but that's probably a long time in the future, if ever. We must live instead with their echoes and the cultural memories and stories of the descendants of the people who once lived among them.

Note: cross-posted on my bird blog at http://geotripperbirds.blogspot.com/

What happens when a Canada Goose goes on a tropical vacation?

Can you imagine a four foot long goose? That's what happens when a Canada Goose decides to take a tropical vacation and chooses to stick around.

I've been developing another blog over the last few months as an outlet for my new hobby, bird photography (Geotripper's California Birds). I'm not an expert (yet), nor a hard-case birder (yet), but my friends and coworkers have come to recognize that if I'm walking around somewhere, I am inevitably carrying a camera. The blog is mostly about my bird observations in California and the west, but I started getting interested in birds during my travels in Hawaii beginning in 2002. I consider these two separate projects, but sometimes the subject matter overlaps. Evolution is one of those subjects, as is hot spot volcanism (i.e. Hawaii). What follows is today's post from the California Birds blog:

Perhaps 500,000 years ago, a pregnant Canada Goose, or a small flock of geese took a wrong turn. A really wrong turn. Somehow, flying along the coast of North America, the leader maybe decided to take a short cut, and it went poorly. Soon the shoreline was lost to view, and for days, not a single bit of land could be seen. I can imagine the flock becoming smaller and smaller as the weaker members fell behind and were lost.  After days of nothing but ocean, an island came into view. The tired geese landed and began looking for food. None of the plants were particularly familiar, but some proved edible and a few of the geese survived. For all we know, some of them rested up and left for further journeys, but a few stayed around. They took up residence on the volcanic island in the tropics of the Pacific Ocean, a vastly different environment than their summer home in the Canadian Arctic. The isolated volcanic edifices are today called the Hawaiian Islands.

During the millennia that followed, different flocks of geese took up residence in different ecological niches, such as lava flows, grassy slopes, and woodlands. Isolated groups began to diverge, and before long at least three species developed on the islands. One of them, the Giant Hawaiian Goose (species name not yet established), was big, almost four feet long. A lack of predators on the island made flight an energy-intensive but unneeded luxury, so the wings became smaller as the bird evolved to larger size. The goose was flightless. This worked fine for a long time, but humans ultimately arrived on the islands, and probably exterminated them, either by hunting, or by introduction of egg-eating rats, or by habitat destruction.

The second species was the nene-nui (Branta hylobadistes). It was also a big bird, but had larger wings so that it was still capable of weak flight. Like the Giant Hawaiian Goose, it became extinct soon after the arrival of humans on the islands. It has been characterized as a bird in evolutionary transition, in the midst of losing the ability to fly, but it went extinct first. Possibly because it couldn't fly well.

I didn't mean that as a flippant remark. Evolution is a process that has provided the incredible diversity on our planet, and isolated islands have provided the crucible in which much of the planet's diversity has arisen. But birds and other animals that have adapted to very specific situations are vulnerable when those situations are changed. The two extinct Hawaiian geese species were secure on the Hawaiian Islands, but the arrival of humans changed their environment too much and too fast. They were certainly easier to capture than a bird that could escape by flying.

The flying goose, the one that survived was the nene (Branta sandvicensis). The nene's wings were smaller than its Canadian ancestors, because it didn't need to migrate thousands of miles during the change of seasons. But it retained enough flying ability to escape from the island's human invaders. It differed from the Canada Goose in several other respects, including longer legs, reduced webbing between its toes, and a more erect posture. It is adapted to living on lava flows and grasslands, and was less dependent on wetlands than other geese.

It survived, but no longer thrived. Rats ate their eggs and chicks, and later on cats and mongooses were brought to the islands. The species was devastated, dropping from an estimated 25,000 when first European contact was made in 1778 to thirty individuals in 1952. A captive breeding program began, and populations were established on their ancient habitats on Maui and Kauai (where mongooses were never introduced). The wild population is now around 800, with another thousand or so in captivity. They are still highly endangered, but their prospects are slowly improving. They have been named the state bird of Hawaii.

My travels in Hawaii were part of the inspiration for my new-found love of bird watching and bird photography. I've seen the nenes (pronounced "nay-nay") on Maui at Hosner Grove (the top picture), and on the flank of Kiluaea in Hawaii Volcanoes National Park on the Big Island (the other two pictures). It is awe-inspiring to observe the descendants of a few very unlucky Canada Geese (or lucky?) who made a wrong turn 500,000 years ago and survived a terrifying journey over a very large ocean. I'm glad were trying to help them survive, instead of driving them to extinction.

Are you interested in learning a bit more about these fascinating creatures? Here is a link for a National Geographic article on the evolution of the Hawaiian geese and their Canadian cousins, and the scholarly article of the research into the vanished species:

 http://news.nationalgeographic.com/news/2002/02/0206_020206_canadiangeese.html

 http://www.pnas.org/content/99/3/1399.full

Time Beyond Imagining - A Final Struggle for Life on the Colorado Plateau

...the massive creature wandered slowly through the dry grasslands. It had been a long hot year, something that had been all too common during the decades the animal had been alive. Foraging was difficult, and the creature was near the point of starving. The large elephant-like animal felt vaguely lonely; it was a herd creature, but it had actually been years since he had seen another of his own kind. He was aware of the pack of predators that had been following him for several days now. They too had the look of hunger, too thin, gaunt, with intense yellow eyes following every movement of the mammoth, but not quite desperate enough to try attacking such a huge beast. They could see it was weak, and they hoped for an opening.

The elephant could smell water. There was stream nearby, maybe a promise of green grass. The trickle of water lay at the base of a dangerously steep slope, but the mammoth was becoming desperate. He carefully stepped over the ledge and started down the rocky slope towards the water. Disaster! Somehow a rock slipped, and the animal lost his footing and tumbled down the slope. There was a crunching sound, and a horrific pain shot through the creature's leg. Something was terribly wrong now, and despite his struggling, he could not stand. The wolves heard the commotion. What was a tragedy for the mammoth was the temporary salvation for the giant wolves. They moved in, and in the moments that followed, the very last individual of the elephant clan on the Colorado Plateau passed into oblivion. Though they ate their fill that day, the wolves were doomed too. In these final centuries and decades of changing climate, they would find fewer and fewer of the large creatures they had evolved to consume, and they too soon passed into oblivion...

The story I've just told is entirely fanciful, with no direct basis in reality. I'm not describing some paleontological excavation, because we don't have one that is known to be the final individual of a species. But the fact is, numerous species became extinct during the last 10,000 years, and there was a final living individual mammoth. There was a final pack of dire wolves, though not at the same precise time. My little story could just as easily have included human beings who stood over the dying mammoth instead of wolves. Anthropologists argue the point.

The last few thousand years of geologic events of the Colorado Plateau are really mostly biological in nature. And to me they represent one of the saddest episodes in the entire two billion history of life in the region. In the last two million years before the present, the canyons and mountains, mesas and buttes of the Plateau looked much as they do today with one major exception. An ice age gripped the world, with a dozen or more cold periods when ice advanced across the northern tier of the North American continent. Though the ice never reached the plateau country, the climate was cooler and wetter, and forests covered what are now sagebrush flats, and sagebrush covered what are now barren desert expanses.

In this environment of rich vegetation growth, a complex ecosystem evolved, with numerous large species of plant foraging mammals, the megafauna of North America. The species that lived on the plateau included mammoths (2nd photo), mastodons (1st photo), camels, giant sloths, bisons, horses, musk ox, bighorn sheep, and mountain goats. They were preyed upon by giant American lions (4th photo), saber-tooth cats, dire wolves (3rd photo), and occasionally by short-faced bears. The lions were bigger than their African cousins, the wolves and bears bigger than their living relatives by a factor of 50%. They had evolved to take down large prey.

These species lived across the continent, and the pictures above are actually specimens from southern California. They are examples of some of the incredible discoveries from the La Brea Tar Pits, where animals were trapped by the hundreds in the black goo. The animals thrived across the land for several million years, but around 10,000 years ago nearly all of them went extinct. Their disappearance coincided with two events: the end of the latest ice age, and the arrival of humans on the North American continent. Which brought about their end? Was it a combination of factors? We don't really know yet. There have even been some suggestions by researchers that an asteroid impact affected the North American megafauna.

In any case, I feel a sense of loss that these animals are gone. Part of the adventure of visiting a national park like Yellowstone is to see the bare remnants of this megafauna: the moose, elk, buffalo and grizzly bears. What an adventure it would have been to see mammoths and other giants wandering the mesas and buttes of the Colorado Plateau!

We've nearly reached the end. I have been exploring the geology of the Colorado Plateau for well over a year now, and one final major event in the geological story remains to be explored. Next time!