The unique ecology of human predators

Humans are ‘unique super-predator’

Fish

“We can tackle adult prey at minimal cost, and so gain maximum, short-term reward, explained Prof Darimont from the University of Victoria (UoV), Canada. “Advanced killing technology mostly excuses humans from the formerly dangerous act of predation,” he told reporters. “Hunters ‘capture’ mammals with bullets, and fishes with hooks and nets. They assume minimal risk compared with non-human predators, especially terrestrial carnivores, which are often injured while living what amounts to a dangerous lifestyle.”

…Prof Tom Reimchen, a UoV co-author on the study, uses a financial analogy to explain the damaging consequences of hitting adult populations hardest. He calls the adults the system’s “reproductive capital” – the equivalent of the capital held in a bank account or a pension fund. And he says we are eating into this capital when we should really be living off the interest – the juveniles, which many species will produce in colossal numbers, expecting a good fraction to be doomed from the moment they are born via predation, starvation, disease, accidents and more. The heavily biased preference for adults was not a sustainable strategy long-term, which ought to be clear from fundamental biology, argued Prof Darimont: “In the overwhelming number of cases as fishes age, they become more fecund. That is to say, they produce more eggs, have more babies, and, in fact, in many cases, many of those babies are more likely to survive and reproduce themselves. “So when a predator targets that reproductive age class and especially the larger more fecund animals in those populations, we are dialling back the reproductive capacity of populations.”

…However, much of the standard conservation management today is based on the notion that it is the “tiddlers” that should be let go, to ensure robust numbers for the next generation. Trawl nets are often designed specifically to support this approach. Doing it the other way would be challenging, but the technical solutions were available, said Prof Reimchen. “There are traps that can define the entrance to a net, which then very easily allows you to exclude fish above a certain size – in other words, the reproductive capital. Once the motivation is in place, clever people will work out how this transition from the reproductive capital to the interest could be brought about.” As for quotas, these should more closely align with the numbers taken out by natural predators, the team suggests.”

read the paper online here

http://www.sciencemag.org/content/349/6250/858.full

or download the PDF here

The unique ecology of human predators

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