If you went back a million years to a Bay Area ridgetop, you might think your time machine was broken. You’d glimpse a bay through trees like today’s, and a passing songbird or squirrel would resemble living species. Roaring and snarling from the canyon below might sound like a motocross. The illusion of modernity would fade, however, as you heard something coming up the hill. Motorcycles don’t breathe in deep, hoarse pants.
When that something came into view, it’s hard to say what you’d think. You might think it was a bear, since it would have a similar massive, plantigrade presence, but you might not, since it would have much longer legs than a modern bear’s and a shorter, deeper muzzle. Whatever your impression, you’d probably be scared, with reason, since the beast — now known as the short-faced bear (Arctodus simus) — was not only very big, but probably also as swiftly predaceous as it looked.
More roars from below, however, would indicate that Arctodus was in retreat from something, and its departure would be as swift as its arrival. If curiosity then overcame fright, you might be fairly safe in going downhill to investigate. Two saber-toothed cats and a pack of dire wolves would be too busy squabbling over the camel carcass from which they’d driven Arctodus to notice you. You might be more wary of some watching mammoths, which were probably like elephants today in getting testy around predators. And you might be unnerved by the numbers of waiting scavengers — foxes, coyotes, vultures, condors, and larger birds called teratorns. With so much going on, you might not even notice more beasts farther away — deer like today’s blacktails, four-horned ungulates resembling pronghorns, and two-horned ones like musk oxen, as well as ground sloths, horses, and peccaries.
Most of these creatures would seem exotic among familiar live oaks and redwoods, but we know they occurred here because their bones remain. In fact, the Bay Area contains North America’s most significant collection of fossils from the period, from 1.2 million to 500,000 years ago. In 1936, teenage fossil hunters found a large deposit in a gravel pit near the Alameda County town of Irvington (near Fremont). Because of the deposit’s species diversity, paleontologists refer to it as the “type location” for the period, which they call the Irvingtonian age.
Despite its importance, the Irvington site isn’t well known even in the Bay Area, perhaps because Los Angeles’s La Brea tar pits have eclipsed it. The tar pits’ scientific significance is similar — they are the type location for the Rancholabrean age, which followed the Irvingtonian. (Both were part of the Pleistocene epoch, which lasted from 1.8 million to 15,000 years ago.) But La Brea’s fossils are lavishly displayed at the site’s museum, while Irvington’s are kept in drawers at UC Berkeley. The La Brea animals’ sensational deaths in tar give them a macabre glamour, whereas the deposition of the Irvingtonian fossils in river and creek beds was far more ordinary and gradual. But extraordinary or ordinary, both ages were typical of the period following the late Paleozoic Era — some 200 million years ago — in that they were characterized by the domination of groups of big herbivores, carnivores, and scavengers. These are referred to as megafaunas, a term mainly applied to mammals now because they have predominated since the dinosaurs’ disappearance, but one that can include big birds and reptiles. Megafaunas as spectacular as the Irvingtonian prevailed almost everywhere until about 15,000 years ago, when they rapidly began to disappear, leaving only relicts like East Africa’s or Yellowstone’s. The precise causes of the disappearance remain little understood, although human population growth definitely contributed. The effects of the disappearance are even less understood, but are more important, because they will impact the planet’s future.
The plants and animals alive today coevolved with these assemblages of large animals, so ecologists worry about the long-term impacts of losing megafaunas. Daniel Janzen, a biologist who works in Central America, notes that many tropical plants have large, hard, tasty fruits adapted for big mammals like horses, ground sloths, or mammoths, to eat. He thinks many of these plants have become scarcer since megafauna disappeared, because the mammals that coevolved with them helped to spread and germinate their seeds. He thinks that some of the plants have become exinct, and that more may follow. Then many other animals and plants that interact with them (as pollinators, browsers, nesters, epiphytes, etc.) may dwindle too.
In the national park where he works, Janzen has tried to restore some megafaunal influence by allowing controlled browsing by livestock like cattle and horses. Many other biologists are thinking about megafauna restoration, including reintroduction of native large wild animals as well as domestic counterparts. Some dream of resurrecting extinct species like mammoths by cloning them from fossil DNA.
Of course, restoring large wild animals is complicated in an urbanized region. On the one hand, an Irvingtonian-like fauna of more than a dozen wild herbivore species supporting as many big predator and scavenger species would need more space than even our largest wildlands could provide. On the other hand, our woodlands, chaparral, and grasslands coevolved with such faunas, and restoring them, at least to some extent, might ameliorate some of our problems in sustaining those ecosystems. Oaks might reproduce better, for example, if more kinds of big animals were spreading acorns, and fire might be less of a threat if there were more browsers and grazers.
A more diverse megafauna would certainly make local wildlands more exciting. Although we don’t want big wild animals roaming the streets, humans have an affinity for them, since we too coevolved with them. As Thoreau wistfully wrote in 1850s Massachusetts, where even deer had been extirpated, “We must be refreshed by the sight of inexhaustible vigor, vast and titanic features . . . We need to witness our own limits transgressed, and some life pasturing freely where we never wander.”
If we were to restore some formerly native megafauna to the Bay Area, what kinds might we hope to see “pasturing freely”? The short-faced bear, Arctodus, would be unlikely because it has no close living relative, but several other Irvington animals do. An Irvingtonian age cheetah left its bones in the Sacramento Valley, for example. Cheetahs lived throughout the west, and may have evolved on this continent before migrating to Africa. Paleontologists think cheetahs are the reason why pronghorns can run 40 miles an hour, faster than living North American predators.
Cheetahs haven’t lived here for at least 15,000 years, however, which raises the question of exactly what an ecologically functional native megafauna for the Bay Area might be. Would it be the animals that lived here when humans first arrived, some 40,000 to 12,000 years ago? Would it be the animals that lived here in historical times? Could there be some kind of “ideal” megafauna for this region — maybe a little closer to the Irvingtonian’s than today’s — that land managers might try to approximate?
In order to address these questions, we have to look at local history as well as prehistory. It’s unclear exactly when the big Pleistocene mammals — mammoths, saber-tooths, ground sloths, camels, horses, peccaries — disappeared, but they were gone by the time Europeans arrived. The California grizzly, which could weigh over half a ton, was the only real giant remaining, and some animals common elsewhere in North America were missing or scarce here. Bison, the biggest surviving native mammals, immigrated here from Eurasia during the Rancholabrean, but didn’t occur in historical times in California except in the northeast part of the state. Wolves, the continent’s top predators, and the only ones to frequently tackle bison, were not historically numerous in the Bay Area. Besides grizzlies, our historically common species — mountain lions, coyotes, pronghorns, elk, black-tailed deer, condors — were on the medium-to-small side of the prehistoric scale.
Bay Area megafauna impressed European explorers anyway. A journal from Francis Drake’s expedition described thousands of “very large and fat deer” on the coast in 1579. Two centuries later, in 1772, Pedro Fages reported “plentiful game, such as deer, antelope, elk, bear,” while Juan Crespi saw bears and deer in the Oakland estuary and “many antelopes and tracks of bears” in the San Benito Valley. Grizzlies thrived on Spanish livestock. A French explorer, A. Duhaut Ceilly, found the bears so abundant in 1827 that “without going farther than five or six leagues from San Francisco, they are often seen in herds.” The abundance didn’t last long. Local ranchers and hunters killed bears, elk, and pronghorns for meat, hides, and tallow. Miners killed condors for their quills, used to store gold dust. By the 1890s, all these large animals were gone from the Bay Area.
At the same time, with our accidental or deliberate help, other kinds of wild or semi-wild animals were appearing here, filling niches vacated by departed megafauna. Livestock escaped to open range, and mustang herds grew so large that vaqueros massacred them during droughts to save forage for cattle. Mustangs disappeared by the 1900s, but feral pigs survived. In the 1920s, landowners near Monterey released Eurasian wild boars for hunting; these bred with feral pigs (sows can bear a dozen piglets a year) and spread to 28 California counties by 1985. In the 1960s, the California Department of Fish and Game introduced wild turkeys as game animals. Weighing the same as condors, turkeys dominate the ground-dwelling avian niche as condors do the soaring one. (Although historically absent from California, turkeys were common during the Pleistocene, albeit as a different species than today’s.)
In the 1970s, the state legislature mandated that the Department of Fish and Game restore historically native species where feasible. Elk, which entered North America from Eurasia during the Rancholabrean age, were the biggest ungulates in the historic Bay Area. Tule elk, central California’s native subspecies, thronged brushy grasslands and marshes before hunting reduced them to a few individuals in the southern San Joaquin Valley. The population recovered under protection, and small groups from valley wildlife refuges multiplied locally after reintroduction to fenced areas at Point Reyes, Concord Naval Weapons Station, and Grizzly Island (in the Delta). The Tomales Point herd at Point Reyes has grown from eight cows and two bulls in 1978 to more than 400 today. Some animals from that herd were moved to form free-ranging herds. Natalie Gates, wildlife biologist at the National Seashore, told me a herd of 28 set free near Limantour Beach in 1999 has grown to 36, with six calves born since 2002.
Terry Pomasano, a Fish and Game biologist, said that elk released near Mount Hamilton have grown into three herds, one moving north to San Antonio Reservoir, another east toward the San Joaquin Valley, and another staying near Mount Hamilton. “Tule elk are a real success for the state,” Pomasano told me. Tule elk do well here because they are prolific and adaptable. The Point Reyes herd, for example, gets a lot of its food by browsing an alien weed, the plantain. But attempts to reintroduce other native species have been more problematic.
No North American mammal is more native than the pronghorn, which is not an antelope as explorers assumed but the last survivor of a group, the antilocaprids, that has inhabited this continent for 15 million years. Pronghorns have recovered from near-extinction in much of the West, but little of their valley grassland habitat remains here, and they are less prolific than elk. When Fish and Game released some near Mount Hamilton at the same time as the elk, the result was inconclusive. One source told me they’d drifted north toward Livermore and disappeared; another said some had stayed near Mount Hamilton and grown to a herd of about 40. Looking for myself seemed the only way to resolve this. Through the generosity of local pilot Saul Chaikin, I flew over the private ranch where the pronghorns were said to live. Finding animals wasn’t easy at a thousand feet, but I believe a scattering of beige specks near a group of larger beige-and-brown ones were pronghorns associating with elk. (I know the larger specks were elk.) Forty pronghorns aren’t many compared to the 40-fold elk increase at Tomales Point, however, and Fish and Game doesn’t plan to release more in the Bay Area. Point Reyes is the only other potential site, and biologists aren’t sure the species lived there historically.
Condor restoration here is also problematic since the closest population is on the Central Coast near Monterey. The Ventana Wilderness Society began reintroducing condors to Big Sur in 1996, and is releasing six more at Pinnacles National Monument at the end of 2003. If the Central Coast population grows to the goal of 50 birds and roams far enough north, condors might once again fly over the Bay Area. But it will take awhile. Condors are very social, and Central Coast birds like to visit the ones around Santa Barbara, so they’re more prone to roam south than north. Gaps in the ridgelines between the Bay Area and Central Coast also work against northward movement, because they weaken the thermal air currents condors like to ride.
The Ventana Wilderness Society has no plans to release condors north of Pinnacles, and there are no official plans to reintroduce other native giants in or near the Bay Area. California grizzly restoration has eloquent advocates, but they don’t talk much about releasing half-ton bears in this populous region. Self-restoration of natives might be another possibility, however, and a candidate came forward in May 2003, when a black bear was seen raiding the dumpster of the Point Reyes Youth Hostel near Limantour Beach, the first Marin bear sighting in a century. Further sightings were reported through late July at a dozen sites, from Tomales Bay
State Park to Kirby Cove on the Golden Gate. Hair DNA and scat samples showed that the individual was a male with a taste for fruit, seeds, and paper towels. Biologists guessed he had wandered down from the population in Sonoma County. On October 27, 2003, there was another black bear sighting near Mount Tamalpais; whether this was the same bear is unknown. It’s not certain that black bears occurred historically in Marin County. A letter to the Chronicle after the May 2003 sighting said that only grizzlies did, a view held by Tracy I. Storer and Lloyd P. Tevis in their 1955 classic, California Grizzly. But Marin’s conifer and hardwood forest is certainly suitable black bear habitat.
Black bears do seem to have been absent historically from the drier East and South Bay. Grizzlies may have excluded them, although the two species coexisted in the Sierra Nevada and North Coast. After grizzly extirpation from the state in the 1920s, the smaller species (seldom weighing over 300 pounds) spread from the southern Sierra into the Central Coast Range, and north to the Santa Cruz Mountains. Biologists think they may spread farther, so we may be getting black bears from both sides. Since the 1980s, because of changes in habitat and hunting laws, California’s estimated population has grown from 10,000 to 30,000.
If black bears arrive, they’ll enter a realm of controversy, and not just with local ranchers. Many environmentalists see large introduced animals as threats to ecosystems already hammered by humans. Think of Hilda and Alphonse from Farley descending on painstakingly restored coho and steelhead runs. More to the point, wild pigs rototill entire hillsides as they dig for roots and bulbs, uprooting rare plants and eroding soil. Pigs and turkeys compete with natives for acorns and other foods, and may eat threatened animals like red-legged frogs. Impacts have been judged harmful enough to justify control measures. Local state parks have pig-trapping programs, but control is expensive, however, and usually temporary. Terry Pomasano said the only permanent way to extirpate pigs from an area is to fence it, remove every pig, and keep it fenced.
The pig situation has a corollary that may represent a missed opportunity. Some Irvingtonian animals were pig-like, such as peccaries of the genus, Platygonus, and probably played a similar ecological role. (Rototilling may threaten rare species in today’s shrunken wildlands, but it also benefits plants by spreading propagules and root-symbiont fungi.) Platygonus was long thought extinct, but in 1972, scientists in the remote Paraguayan Chaco discovered a living genus, Catagonus, very like it. Introducing Catagonus here might have been a way to help a threatened species while filling our rooting niche with more manageable animals than pigs. But pigs now hog the niche, an object lesson in the folly of careless meddling with nature.
Given such difficulties, could what we have in the Bay Area now be called a functional megafauna? Large wild animals certainly are less common than two centuries ago, and nobody thinks that today’s unplanned melange of natives and exotics is ideal. So far, we haven’t succeeded in restoring the feasible historic megafauna here, much less any
of the prehistoric. If we ever want to restore cheetahs, we’ll have to restore pronghorns first.
Still, our present megafauna does have strong points. Native black-tailed deer remain common. Coyotes and mountains lions survive, providing more long-run herbivore control than we can. Despite the problems, Bay Area ecosystems are
better for the big wild animals that live here. That’s hard to prove in light of our limited understanding of megafauna’s ecological role. But my own experience in three decades of hiking local wildlands suggests it. That may be because they are the most remote and undisturbed places, but not necessarily. I’ve seen more zoological exuberance around the elk at Tomales Point and Limantour than on many walks through the more remote, but elk-less, southern part of the Phil Burton Wilderness.
One October day in 1994, for example, I saw three long-tailed weasels at Tomales Point, more than I’ve seen elsewhere in one day. I also saw a burrowing owl, which I haven’t seen elsewhere at Point Reyes. One foggy afternoon in May 2001, every other coyote bush at Limantour seemed to have a young rabbit under it, and one bush had a coyote under it, the first I’d seen there. That August, I witnessed a mass migration of quail near Limantour, hundreds trooping up an elk-browsed hillside. I’ve seen quail all over the Bay Area, of course, but not hundreds in one place. Naturalists have often remarked on the abundance of smaller animals around megafauna. Big wild animals may improve habitat for smaller ones by diversifying vegetation with their activities. Daniel Janzen writes that landscapes “moderately and patchily browsed” by a variety of big animals “may be more like those before megafaunal extinction than were those present at the time of the Spanish conquest.”
One thing is certain. If a place is big enough for elk and pronghorns, it’s big enough for a lot of things. And while herds of mammoth are probably out of the question, a few megafaunal monsters moving around the landscape might be a good antidote to the monstrous mega-homes now crawling up our hillsides.
Most recent in Human History
By sinking Doyle Drive into a tunnel, the Presidio has created an additional 13 acres of open space. Now the question is how to use it -- and the Presidio Trust wants the public to help decide.
Habitats: Land | Human History | Recreation | Urban Nature
Mountain biking is among the fastest-growing recreational activities in the East Bay Regional Parks. Follow along for a ride with Austin McInerny of the National Interscholastic Cycling Association.
Habitats: Land | Human History | Recreation