Stolzenburg, William. 2008. Where the Wild Things Were: Life death, and ecological wreckage in a land of vanishing predators. Bloomsbury, NY: Bloomsbury
(Summarized by Kelly Kapsar, Animal Studies Graduate Program, Michigan State University)
Where the Wild Things Were, written by wildlife journalist William Stolzenburg,weaves together some of the most prominent figures from 20th century ecology to present a unique and integrated view of ecological research on the top predators of North and South America. In doing so, he highlights their invaluable role in promoting biodiversity and ecosystem function. By retracing the interwoven footsteps of some of ecology’s greatest researchers, Stolzenburg uncovers the ecological havoc wreaked by the systematic destruction of top predators and discovers that “the biggest and scariest of carnivores were more dangerous by their absence” (Stolzenburg, pg. 3).
The narrative begins with story of Charles Sutherland Elton, the Arctic tundra, and the birth of the field of community ecology. Whereas previous research had focused on cataloging the diversity of life and relating them through morphological similarities, Elton “had caught a glimpse of the glue that held them all together” (Stolzenburg, 10). Through his research and subsequent publications, Elton described the essential nature of food and the way that the transfer of energy, through food, linked ecosystems together in webs. Additionally, Elton noted decreasing abundance as distance from the sun on the food chain increases. In other words, on Earth there are more plants than herbivores and more herbivores than carnivores. Perched at the top of many food webs are the apex predators. These are the lions, the tigers, and the bears of the world. Or, in Elton’s case, the arctic fox. But what keeps the carnivores from eating all of the herbivores and what keeps the herbivores from eating all of the plants?
Two different approaches have been used to explain the inherent “balance of nature”. According to the “bottom-up” hypotheses, prey and predator species numbers are kept in check by competition for food. If there isn’t enough grass, the zebras will consume all the grass that’s available and subsequently starve to death. Opposite of the “bottom-up” hypothesis is the “top-down” hypothesis. Stolzenburg provides evidence to support the “top-down” control of prey populations by predator species, also known as the “Green World Hypothesis”. This concept, first introduced by the scientists Hairston, Smith, and Slobodkin (also known as HSS), posits that the world is green because predators control prey numbers so that prey species are unable to consume all available plant material.
To illustrate this point, Stolzenburg turns to the rocky cliffs of the Pacific Northwest and a young man named Robert T. Paine. Paine was interested in the intertidal communities that inhabited the rocky cliffs along the shores of the Pacific Ocean. Various species of snail, conch, whelk, clam, and muscle inhabit this zone and space was at a premium as organisms struggled to hold on to the rock face without being dashed away by waves. At the top of the food web is Pisaster ochraceous, the ochre starfish. Pisaster is a predatory species that consumes muscles by ever so slowly prying them open and injecting its stomach outwards, digesting them in their shells. To Paine and his successors, this was the perfect system in which to test the power of top carnivores. And the way to understand their power was to remove them. So Paine set out to pry off starfish from a section rock cliff and chuck them back into the ocean. After less than a year, a great change in the intertidal community had occurred. In the absence of Pisaster, the mussels that represented its former prey had now out-competed many of the other species, so much so that seven of the original fifteen species had left entirely. This research provided compelling evidence to support the Green World Hypothesis and the importance of top predators in an ecosystem.
In the second chapter, Stolzenburg examines the evolution of apex predators across history, from the earliest single-celled organisms developing tails and chasing cells across the world’s oceans to the relative paucity of large-bodied predators in the modern day. Around 565 million years ago, organisms evolved from gelatinous masses into shapes and forms relatable to many modern day animals. Many of the creatures that evolved during this time possessed hard shells used for defense in the arms race that was later known as the Cambrian Explosion. Evidence derived from a diversity of fossils with apparent bite marks indicates that this era marked the beginning of the modern complex food web system. Around 350 million years later, the Mesozoic Marine Revolution was a time of escalation in size. The rise of the mammals and birds on Earth occurred around 65 million years ago after the infamous asteroid strike decimated dinosaur populations. Previously small, mouse-like creatures subsequently evolved into a diversity of species, including all of the major lineages of predatory mammals. It was during this time that spiked canine teeth for gripping and carnassial teeth for shearing meat arrived in the fossil record.
In the wake of the evolution of large carnivorous mammals came a rather small and fleshy species with little in the way of claws or teeth, but an abnormally enlarged brain. In the scope of Earth’s history, humans are a relatively new development. However, within a half a million years of their first appearance, humans had already begun to eliminate both large prey species and their fellow predators. This tendency toward destruction of predatory species was fostered by the advent of domestication, through which “…were born two new and related concepts: one viewing animals as property, the other assuming predators as thieves and threats to livelihoods” (Stolzenburg, 46). The systematic elimination of predators was particularly rapid in North America in the early 20th century as a result of state-sponsored programs rewarding hunters for eliminating animals such as wolves, coyotes, golden eagles, mountain lions, and other “vermin”. These actions resulted in the unintentional creation of a continent wide experiment on the effects of large carnivore removal in ecosystems.
The third chapter of Where the Wild Things Were follows the scientific research of James A. Estes in the Aleutian Islands in Alaska. Stolzenburg uses Estes’ research as an introduction to the concept of a trophic cascade, whereby the removal of the top predator in an ecosystem has “cascading” effects on lower rungs of the food chain. In the case of Alaska, sea otters were hunted to near extinction by the turn of the 20th century. Small populations survived on a few remote islands, while others were left entirely empty. Estes, after a passing discussion with Robert T. Paine about the ability of urchins to decimate kelp forests, began to research the effect of otter absence on kelp (Otters are, first and foremost, the primary predators of sea urchins). He discovered that islands with a scarcity of sea otters possessed an overabundance of sea urchins, and a subsequent lack of kelp. Alternatively, islands inhabited by otters had relatively few urchins and maintained kelp habitat that supported numerous other species.
Stolzenburg further complicates the tale of the sea otter in chapter four, “The Whale Killer”. Around the end of the 20th century, Estes’ sea otter populations began to rapidly decline without any apparent impetus. The decline, however, was not universal. While the otter population Estes had previously been monitoring was taking a substantial hit, otter numbers in a relatively close bay remained stable. After a research assistant witnessed an otter being eaten by a killer whale, a new hypothesis was formed. Metabolic calculations revealed that as few as 3.7 killer whales could be responsible for the decimation of Estes’ otters, but the question of why killer whales would suddenly turn to eating popcorn-sized prey remained. To answer this question, Estes and his colleagues turned to the history books and whaling in the Pacific Ocean.
Killer whales are the top predator in the oceans. As pack hunters, they have been known to viciously attack pods of whales. However, industrial whaling had left killer whales lacking this prey source. Given this information, Estes hypothesized that “[f]or want of larger prey, killer whales had begun picking off the next convenient prospects down the line, from harbor seals to Stellar sea lions to sea otters, which had apparently collapsed in suspicious sequence across western Alaska” (Stolzenburg, 74). This hypothesis, while intriguing, could not be empirically tested, and also challenged the widely held belief that Stellar sea lion populations were declining due to overfishing of their primary prey (a bottom-up control), rather than the top-down influence of predation by killer whales. Verifiable or not, Estes’ hypotheses expanded the dialogue surrounding the influence of top predators in an ecosystem.
In chapters five through nine, Stolzenburg catalogues trophic cascades and their impact on ecosystems across the Americas. In chapter five, Stolzenburg follows the research of John Terborgh and the concept of ecological meltdown. Terborgh’s research highlighted the loss of biodiversity associated with the creation of islands that were not large enough to sustain populations of carnivores. In particular, the construction of the Raul Leoni Dam in 1990 and subsequent creation of Lago Guri left pieces of land that had previously served as hill tops surrounded by water, thus creating new islands. By 1993, when Terborgh and his team arrived on the scene, three quarters of the species present on the mainland had already disappeared from the islands. The effect was similar to Terborgh’s previous experiences with the formation of Barro Colorado island and its loss of species. In particular, rates of predation on bird eggs increased on the islands where animals like the coati, whose numbers had previously been kept in check by jaguars, thrived.
One such species were the red howler monkeys. In the absence of large carnivores on the islands, howler monkey social organization devolved as individuals spent more time alone, stopped grooming, and stopped howling. For lack of a better explanation, researchers concluded that the monkeys just did not get along anymore.
A species that received a substantial boost from the formation of the Lago Guri islands was the leaf-cutter ant. In the absence of their chief predator, the army ant, leaf-cutter ants thrived and left bare branches and dead trees in their wake. In the place of trees grew thorny vines that were unpalatable to the leaf-cutter ants. Thus, in the presence of leaf-cutter ants, tropical forests experienced an “ecological meltdown” and were converted to uninhabitable patches barren of their previous biodiversity.
Chapter six, “Bambi’s Revenge”, returns to mainland North America and the effect of exploding deer populations on forest biodiversity and ecology. After the removal of large predators and increasing deforestation of the 19th and 20th centuries, deer populations across North America surged. As a generalist species, deer eat a variety of plants, such as grasses, flowers, tree buds, fruits, and fungi. As the population size grew beyond historical bounds, plant species diversity decreased. Formerly abundant flowers were only to be found on steep cliffs and an entire generation of young trees in northern Wisconsin was missing. Researchers across North America catalogued the disappearance of species in the absence of large carnivores. Tagging along with the increasing deer population came a resurgence of Lyme disease, passed along to humans through deer and mice. Many individuals and organizations began advocating for deer population control by hunting. However, both hunters, who thought there could never be too many deer, and animal rights advocates, who disapproved of any killing, met conservationists with fierce opposition.
Stolzenburg shifts focus away from prey species in chapter seven, and turns his gaze toward missing birds and the mesopredators (“middle” predators) responsible for their disappearance. Like the formation of Lago Guri and Barro Colorado islands, much of North American wilderness was rapidly fragmenting into smaller and smaller “islands”. However, instead of water, the habitat fragments were surrounded by an ocean of humanity. In the enforced absence of their larger counterparts, the raccoons, blue jays, opossums, and other mesopredators of North America had been set loose. The increasing abundance of mesopredators led to a subsequent decline in bird diversity as nest predation rates increased. To illustrate this concept, Stolzenburg follows the research of Michael Soule in the American southwest. By the 1980s, the chaparral habitat was succumbing to the tide of human development. As humans encroached on previously uninhabited land, the diversity of bird species declined. However, Soule noticed another factor influencing the abundance of birds: coyotes. Patches of chaparral inhabited by coyotes had a higher diversity of birds than those without. And cats were the reason why.
Free-ranging cats are commonly glossed over or forgotten by scientists researching predation. However, they were consuming almost 2,000 small mammals, lizards, and birds per year in the average chaparral fragment studied by Soule. In the presence of coyotes, one in four house cats that Soule studied was dead by the end of the study. This decline in cat numbers in the presence of coyotes led to an increase in bird diversity, or as Stolzenburg says, “Where the coyotes roamed, the cats ran scared, and the chaparral birds sang” (Stolzenburg, 133).
In chapter eight, “Valley of Fear”, readers follow Bill Ripple, his graduate student Eric Larson, and the hydrologist Robert Beschta through the aspen groves of Yellowstone National Park. When Beschta first visited in the mid nineteen nineties, he was astonished at the terrible quality of Yellowstone’s waterways. In the absence of tree roots to hold them in place, riverbanks were eroding away, clouding up the water and taking valuable nutrients downstream with them. Around the same time that Beschta was observing streams, wolves were reintroduced to Yellowstone after a seventy-year hiatus.
In the seventy-year absence of wolves, the Yellowstone elk population had decimated willow, cottonwood, and aspen tree saplings, possibly causing the erosion that Beschta had witnessed. However, after their reintroduction, wolves began to exert their power over the ecosystem. Ripple and Larson catalogued these effects and discovered that the reintroduction of wolves had created an “Ecology of Fear” in the Yellowstone landscape. Elk that used to freely graze where they pleased were now spending more time on high alert and refrained from grazing in possibly dangerous zones where they couldn’t run away from wolves. It was in this manner that aspen trees began to grow along steep riverbanks. More so than the actual death of elk, the heighted fear of death caused by the presence of wolves had changed the landscape. This ecology of fear has been demonstrated in a variety of systems across the globe, ranging from grasshoppers that die at increased rates when placed in the same cage as a spider with its mouth glued shut to herons that began foraging only at night when raptors were present on the landscape.
Stolzenburg concludes his examples of trophic cascades with a famous story popularized by none other than Aldo Leopold. The Kaibab Plateau lies on the northern edge of the Grand Canyon and, at the turn of the 20th century, hosted a herd of mule deer. When the plateau was set aside as a game preserve in 1906, both hunters and predators of the deer were removed from the land. By the mid 1920s, the mule deer population had jumped from 4,000 to 100,000 individuals and, in the winters of 1924 to 1925, only one in ten of those deer survived while the rest starved to death.
This cascade was frequently used by ecology textbooks as an example of the effects of removing predators from a system. Over the years, the legend of the Kaibab lost some of its affluence as researchers questioned the relative influence of predators on the deer population eruption, as opposed to other factors, such as the decrease in competition from livestock. However, researchers examining tree growth on the Kaibab have discovered evidence of “aspen quitting production in approximate synchrony with the killing of the Kaibab predators and the eruption of the Kaibab’s deer” (Stolzenburg, 163). Similar to Yellowstone, this research provides evidence that top predator removal was indeed the cause of the mule deer overpopulation on the Kaibab.
Close by, Ripple and Beschta had moved out of Yellowstone and into Zion National Park. Their research focused on the prevalence of mountain lions in Zion National Park and nearby North Creek Canyon. While the Park streamed with tourists, North Creek was relatively undeveloped. Mountain lions, an elusive and shy species, were absent from the overcrowded Zion, but present in North Canyon. When comparing these systems, Ripple and Beschta were able to draw a strong correlation between the loss of mountain lions in Zion National Park and the loss of biodiversity. Biodiversity that was to be found next door in the North Creek.
In chapter ten, Stolzenburg addresses the questions, should we restore large predators? And, if so, how far back should we restore? To examine these questions, Stolzenburg narrates the history of the concept of Pleistocene rewilding. Compelling scientific evidence supports the idea that humans were, at least in part, responsible for the extinction of North American megafauna around 12,000 years ago. Before this extinction, mammoths, saber tooth tigers, cheetahs, giant sloths, dire wolves and other species roamed throughout North America. Like the top predators of the modern era, scientists have reason to believe that the megafauna of the Pleistocene played a significant role in shaping their ecological community.
When conservationists speak of restoring ecosystems, they have chosen Columbus’ arrival in 1492 as the baseline for ecosystem purity. However, given the evidence of human influence over ecosystems long before Columbus, “[i]f restoration was honestly the goal, why not aim for the pinnacle of the Pleistocene?” (Stolzenburg, 176). While many of the species that inhabited North America during the Pleistocene are currently extinct, many of their close cousins still roam the plains of Africa. In short, scientists who advocate for the “rewilding” of Pleistocene megafauna advocate for the release of captive-bred megafauna cousins, such as cheetahs and elephants, in North America. Unsurprisingly, this concept received substantial backlash from both the scientific and public realms. While many people felt threatened and reacted to the idea of lions roaming the range, few people reacted to the author’s primary argument that the loss of the Pleistocene megafauna had ecological consequences in the same way that the current loss of large carnivores was destroying ecosystem biodiversity.
Where the Wild Things Were closes with a look at the ecological niche of ancient human ancestors. Stolzenburg uses one particular fossil from Australopithecus africanus, nicknamed the Taung child, as an example of the many different ways that humans have reflected on their own ecological role. The Taung child was found in a cave on the edge of the Kalahari Desert in South Africa in 1924 along with the bones of thousands of other species, ranging from baboons to antelope to giraffes. While some researchers took this, along with the preponderance of suspiciously club-like antelope legs bones, as evidence for a “Man the Hunter” hypothesis, others noted the puncture wounds on the Taung child’s skull and used these as evidence for a “Man the Hunted” hypothesis. A third hypothesis, “Man the Scavenger”, emerged after George Schaller, a wildlife biologist, and anthropologist Gordon Lowther decided to see how much food they could scavenge on the Serengeti. After a week and three separate finds (an injured zebra foal, a blind giraffe, and a deceased water buffalo), Schaller and Lowther had support for their hypothesis. Yet a fourth hypothesis emerged from the recognition of human’s incredible capacity for distance running. The “Marathon Man” hypothesis suggests that humans chased their prey to exhaustion and subsequently killed them. In the end, the most compelling evidence for the demise of the Taung child indicates that its death was at the claws of a giant eagle. Scratch marks around the eye socket along with puncture wounds on the skull are all indicative of an eagle attack.
In the final pages of the book, Stolzenburg bring forth the idea of “Man the Haunted”. Most humans live with little threat from wild animals in their daily lives and yet they are still haunted by the thought of their presence. New stories, such as a biker being killed by a mountain lion, make national television, despite the fact that many more people die at the hands of dogs or cars each year than by wildlife attack. Stolzenburg concludes the book by narrating the tale of the pronghorn antelope. Pronghorns, a holdover from the Pleistocene, are the second fastest land animal on the planet, reaching top speeds of more than sixty miles per hour. In the modern day, nothing on the continent of North America can catch them. It is only when we look back at the record that we understand that pronghorn speed is an evolutionary relic, a ghost of the days when cheetahs still roamed the continent.