‘Super predator’ humans harming ourselves: UVic study

Humans are predators that hunt other species to extinction, and our methods are starting to hurt us, say two University of Victoria researchers who used data from more than 300 studies.

Humans are what scientists have taken to calling “super predators” because we kill wildlife and fish at such a high rate. Human hunters also target adults, rather than younger animals, which the researchers say can harm populations.

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“All of the species that humans now exploit had to deal with a range of predators for several million years,” said Chris Darimont, a University of Victoria geography professor and co-author of an article on human predation being published today in the journal Science.

“Then modern humans arrive on scene and with capture methods that circumvent the majority of these prey defences.”

But while the predatory behaviour benefited society in the short term — sustaining livelihoods and allowing the expansion of industry and empires — the effects are “now felt increasingly by humanity,” Darimont said.

Extreme results have ranged from loss of wildlife species in some regions to disruptions in the food chain, according to Darimont and fellow author Tom Reimchen, a UVic biology professor.

Part of the solution could be a different approach to dealing with wildlife and fish, Darimont said. Preserving species such as large carnivores provides examples, he said.

“If future generations of people are to see these magnificent animals, then this requires cultivating new tolerance for living with them,” he said, noting this could include increasing revenues from uses such as ecotourism — shooting carnivores with cameras, not guns.

“In some cases, safeguarding large carnivores threatened by trophy hunting requires societal pressure to drive policy change or to ensure better enforcement. And the moral outrage expressed globally over the death of Cecil the lion tells us that this time could be drawing closer.”

He said humans kill large carnivores such as bears, wolves and lions at nine times the rate that the animals kill each other.

When it comes to fishing, humans go after adult fish, while animals that eat fish concentrate their efforts on fry and juveniles, Darimont said.

“Marine fisheries represent the planet’s dominant predator of adult prey,” he said.

In fact, humans target adult fish at 14 times the rate of animal predators — a total that Darimont said was a surprise to the research team.

“As for fisheries, we reason that non-human predators have stood the test of time as models of sustainable exploitation,” he said. “They rarely, if ever, cause extinction or rapid population decline in prey.

“Therefore, we believe they can provide humanity with behavioural guidance. This includes transferring our targets of exploitation to juvenile age classes and reducing exploitation on adults.”

People have long been directed to target adult prey and leave the rest, Darimont said.

“This paradigm therefore, in fact, instructs fishers and hunters to engage in this rather unnatural, unusual predatory behaviour, and explains why harvesters are required by law to release those undersize fish or set their rifle scope on the six-point elk and not the calf.”

The basis for the article’s viewpoint came from studies that Reimchen started in 1976, looking at predator-prey associations at a remote lake on Haida Gwaii.

“At this lake, I found that there were 22 species of predators, including trout and loons and grebes and otters, feeding primarily on a resident stickleback fish,” Reimchen said. “And despite all these predators, the stickleback population was generally stable across years.”

That is similar to other aquatic communities, he said, noting that less than five per cent of the stickleback preyed upon were adults.

Reimchen said this represents an “ecological disconnect” with commercial fisheries.

Researchers expanded the scope to include information on about 400 species of fish and land mammals from a wide range of areas.

jwbell@timescolonist.com

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