The human ‘superpredator’ is unique — and unsustainable, study says


Los Angeles Times

By Amina Khan, August 20, 2015

If you’re looking for the world’s top “superpredator,” look no further than your own reflection.

A new study that examined more than 2,000 predator-prey interactions in populations around the globe has found that humans don’t only kill top carnivores at a rate far higher than all other top predators combined, but that our particular hunting behaviors are so devastating to species on land and sea that they challenge these populations’ ability to recover — and in some cases could alter the course of their evolution.

“Ultimately, humanity is feeling the impacts of our predatory dominance,” said lead author Chris Darimont, a conservation scientist at the University of Victoria.

The findings, published in the journal Science, reveal the extent of the damage wrought by human hunting and fishing practices, and reveal that there might be hope for recovery — if we learn better practices from the same carnivores that we are hunting down.

“We have the unusual ability to analyze and consciously adjust our behavior to minimize deleterious consequences,” Boris Worm of Dalhousie University, who was not involved in the paper, wrote in a commentary. “This final point, I believe, will prove critical for our continued coexistence with viable wildlife population on land and in the sea.”

Many of the world’s large fish and land-based top predators — your lions, your tigers, your bears — have been on the decline for years, and it’s thought that humans have had a major hand in their downfall. Hunting, along with climate change and human habitat encroachment, all likely play a role.

That’s not a new pattern: Within the last tens of thousands of years, marvelous megafauna — woolly mammoths, saber-toothed cats, giant sloths — roamed the Earth, and many of them began disappearing around the same time that humans arrived in their habitats.

To get a better handle on the effect of human hunting, the researchers collected data on 2,125 predator-prey interactions in different populations on land and sea to calculate the rates at which predators exploited their available adult prey – in other words, what share of the adult population they killed each year. These interactions included both human and other natural hunters.

They found that the human take of adult fish each year was a whopping 14.1 times the rate of other marine predators’ take. On land, humans killed top predators at a rate 9.2 times the rate that those top carnivores killed each other.

“We predicted that there would be difference, but we were surprised by the magnitude of that difference,” said Darimont, who also serves as science director of the Raincoast Conservation Foundation in British Columbia. While other top predators do kill each other occasionally, he added, it’s usually because of competition between members of the same species…

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