The Australian shark cull and the plight of apex predators
“As long as Homo sapiens has been sapient... alpha predators have kept us acutely aware of our membership within the natural world. They’ve done it by reminding us that to them we’re just another flavor of meat.”
David Quammen, “Monster of God”
In Western Australia, along a stretch of coastline about the size of New England’s, seven people have died from unprovoked shark attacks since 2010. In the same four-year period there only five fatal attacks in the entire United States.
The deaths in Australia were eerily similar. Seven men— capable surfers, swimmers and divers—taken by great whites near other people in broad daylight. The Australian media was almost formulaic in its coverage of each attack. Appearing on national television every few months were photos of genial husbands, fathers and sons superimposed over razor teeth and leering black eyes. The message was clear: it could have been anyone. In a country plagued with a fear of sharks since its colonial era, the fish became a full-fledged national security threat.
The spike in attacks puzzled marine ecologists. Despite the animal’s notoriety, the great white shark’s behavior is something of an enigma to scientists. The covert predator’s population size and movements off the coast of Australia are still poorly understood. They do know, however, that the animal almost never deliberately seeks out humans as prey.
Western Australia policymakers, meanwhile, had to decide on a plan of action. The most contested strategy up for discussion was a program to systematically catch and kill large sharks near public beaches. As the attacks continued, the possibility of a cull came into the forefront of the statewide dialogue. Australia lauds itself for its environmental stewardship, so political leaders were at first hesitant to push for a plan that institutionalized the killing of endangered animals. State premier Colin Barnett said in March of 2012, after the fifth fatal attack, that a cull was “not the answer.” Perhaps he was clinging to some hope that the catastrophe would just stop—that the poorly understood animals would get distracted by harbor seals and vacate his waters.
A year later, with two more deaths fresh in the public memory, Colin Barnett appeared on television to debut the state’s freshly minted shark killing arsenal. He held up to the camera a barbed hook large enough to eclipse his head. As part of a $20 million shark prevention program, 72 of these hooks were to be baited and suspended in “kill zones” one kilometer off the coast of popular beaches. Tiger, bull, and great white sharks larger than three meters would be “humanely destroyed”—or shot in the head. The war on sharks was underway.
“The loss of apex consumers is arguably humankind’s most pervasive influence on the natural world,” wrote ecologist James Estes in a 2011 Science review article. In the study he synthesized years of research and reached a stark conclusion: killing off top predators is one of the worst things that can be done to an ecosystem. Apex predators, which occupy at the top of the food web, exert control over the entire ecosystem by managing the numbers of their prey. If they go, populations of what was once their food explode and the ecosystem can radically change. This phenomenon is called a trophic cascade.
It turns out trophic cascades can have much wider ramifications than scientists originally believed. The decline of leopards and lions in Sub-Saharan Africa, for instance, may have an impact on the rise of infectious disease in the region. As predation declined with the drop in big cat numbers, the population of olive baboons in the region exploded. Baboons then began transmitting intestinal parasites to humans at an increased rate. What was at first lamented for ethical and aesthetic reasons became the cause of a major public health problem.
Scenarios like the baboon surfeit are unfortunately commonplace on a planet largely inhospitable for dominant predators not named Homo sapiens. The rise of human beings has incurred a massive toll on the world’s other apex predators. Scientific consensus considers the planet to be in in the midst of its sixth mass extinction, characterized by the loss of apex predators. And this time, instead of asteroid impacts or falling sea levels, humans are the sole source of death.
Bears, wolves, big cats, and sharks have been on endangered species lists since their invention. At this point, there’s a sense that low populations of big predators is a fact of life on earth. In some ways, this is valid. Energy is lost with each step up a food web. An anteater does not acquire all of an ant’s energy, and the anteater’s predator does not acquire all of an anteater’s energy. It follows that there should then be fewer tigers than ants.
Large carnivores also exhibited relatively high extinction rates before humans began to proliferate. It’s not the fact that some large carnivore populations are sparse that alarms conservationists; it’s the rapid rate of extinction across many species, and our role in incurring it.
Big animals were far more abundant and diverse before humans began spreading through new habitats. Giant sloths the size of elephants and saber toothed cats once roamed the grasslands of South America. North America was home to its own species of lion and cheetah.
Paleontologists have noted that the extinction pattern
of these animals and many other large predators matches
up with the timing of our arrival in their habitats. As early humans spread through the planet 50,000 years ago, they became more adept hunters. The predators they encountered in new habitats suffered from the added competition for food. They also hadn’t evolved alongside humans and likely were easily hunted.
This human-driven extinction scenario is just one theory that attempts to explain the sudden death of many large mammals 10,000 years ago. What isn’t subject to conjecture is our decimation of large carnivore populations in more recent times. Humans are horrible at cohabitating with other apex consumers. In fact, we’ve found it difficult to thoroughly develop any region without widespread slaughter of its natural predators.
Take the plight of the gray wolf in America. The spread of agriculture through the American West disrupted the habitat and prey base of our country’s iconic canines. Wolves subsequently developed a taste for a new type of prey that appeared in abundance: domestic livestock. The wolf in this period was a serious threat to the livelihood of settlers, and they developed a vitriolic fear of the animal. Teddy Roosevelt, an early champion of conservation, called the wolf a “beast of waste and destruction.” For decades, the US Government supported the systematic extermination of the American wolf population until just a handful of packs remained in the lower 48 states. Conservation efforts came just in time to rescue the animal from the brink of extinction.
Often people are prone to pardon environmental atrocities of eras past. One may argue that the importance of conservation hadn’t been discovered, or that the animal posed a serious threat to the livelihood of many. But if we exonerate our ancestors we must first take lessons from their mistakes— which have failed to do. Once the wolf population rebounded, some groups claimed conservationists had reintroduced a threat to livestock and healthy elk populations. This is a view unsupported by data and shared by few scientists. Still, Wyoming, Montana and Idaho have again legalized wolf hunting. The characterization of the wolf as a menace to humans has persisted in some parts of our country.
The trial shark cull in Western Australia ran from January to April this year. Of the 172 sharks hooked, 50 measured over 3 meters and were destroyed. 14 more died on the drum lines and 4 were shot because they were determined to be too weak to survive. All 50 large sharks were tiger sharks, which haven’t attacked humans in Western Australia in years. Not a single great white was caught.
The Western Australian government hoped to continue the cull each summer for three more years. Their plans were blocked last week by the state’s Environmental Protection Authority, which cited a “high degree of scientific uncertainty” regarding the cull’s impact on great white populations.
There still remains uncertainty as to why shark attacks spiked in the first place. The most popular theory among scientists seems to be that there are simply more people encroaching on their environment. Reflecting on population growth in Western Australia, shark specialist Rory McAuley said, “If you look at Perth from the water at night, when you can see the lights of the suburbs, you see that it now reaches over a huge stretch of coastline, further than you can see in the north and the south.”
Premier Barnett expressed to parliament that he was “disappointed” with the decision to end the cull. He said, with regards to future, “I think if you have, I’d use the term rogue shark.... I think we need to catch that shark and remove it.” The idea of a “rogue shark” that seeks out humans is an unsubstantiated idea popularized by Jaws. It’s a misrepresentation of the animal that perpetuates a common myth: that sharks are out to get us.
The end of institutionalized shark killing is a victory for both the ecosystem and the thousands of Western Australians who advocated for it. It’s also a triumph for the families of the seven recent victims, whose tragic losses were used to justify a fruitless slaughter.
Still, a deadly mentality remains. TV specials with titles like “Great White Serial Killer” and “Man vs. Fish” attract millions of viewers to Discovery Channel. We continue to reduce this complex animal to a man-eating caricature, just as some cling idea of the wolf as a pest.
Sharks aren’t stalking our shores for human meat, and wolves aren’t put on this earth to eat livestock. We are the ones annexing and altering our fellow predators’ habitats. The threat these animals pose is often our own reckless expansion coming back to bite us. After all, they have been around since long before Perth lit up at night.