Hunters negatively affect the evolution of animals

By Cam Cotton-O’Brien

Amassing data from the last few decades, Dr. Paul Paquet has found some alarming evolutionary tendencies in animal species that are hunted by humans.

His work has not endeared him to trophy hunters.

The adjunct professor at the University of Calgary and his colleagues conducted a meta-analysis of previous studies looking at the impact of human activity on other species. This type of analysis used previous findings to draw conclusions from the collective data.

“Those studies all looked at the effects human hunting, either commercial or recreational, has on those species,” said Paquet. “When we brought all of those studies together and were able to coalesce them, we were able to assess them simultaneously. What we found was that there was a really profound human influence that shaped the animals that were being exploited, and the plants, too.”

That profound human influence includes a roughly 300 per cent acceleration in the rate of evolution for such species as compared to species that are not hunted. In addition, because of the peculiar place of man as a super-predator in the modern world, the mode of that evolution is strange. Because humans have the technology to target the most robust members of a species, human interference results in smaller and possibly weaker individuals.

“The difference was a bit of a surprise to all of us, how rapidly these changes were occurring,” said Paquet. “Typically human, we are after the biggest and the best, so really what we’re doing is high-grading the population.”

The size of the animals and the speed of evolution were not the only abnormalities observed in such species. The study also found that the animals’ reproductive behaviour had changed, they were reproducing at much younger ages. Paquet argued this behaviour occurs because the prime members of the species are being hunted, which opens up reproductive opportunities to less developed individuals, and because animals in that situation are more likely to breed before growing to full size, at which point they become targets.

“In cod fisheries, which have been controversial for some time, over time, females began to reproduce at an earlier age than undisturbed populations,” said Paquet. “One of the consequences of that is that they produced fewer eggs– much, much fewer eggs. That ultimately contributed to a population decline.”

Paquet pointed out that these human pressures are not likely beneficial to the animals and may reduce the viability of the species.

“We don’t really understand all of the repercussions, but we do have examples, from fisheries primarily, where populations are in jeopardy,” he said. “Nearly all are in trouble.”

Technological innovations in human weaponry have been one of the key reasons for the difficult situation this study has unearthed. Paquet noted that humans have always hunted, but that it is only in the last couple of hundreds of years that they have completely moved away from the traditional predatory behaviour of attacking the weakest members of the species and been able to consistently target the most well-developed individuals.

“I’ve always tried to imagine what do you hunt with a spear or a knife,” said Paquet. “That’s got to be pretty limiting.”

Though there has been considerable negative reaction from hunters since the study was published, Paquet pointed out that the reason for carrying out and publishing the study was to disseminate information, not to criticize. He hopes that the information will help guide humans to adopt more sustainable hunting and gathering strategies, one of which he says is developing more wildlife sanctuaries.

“It’s going to have to happen through regulation,” said Paquet.

The study initially included some 50 species, but was eventually pared down to 30 from around the world for which there was sufficient data. Of these, the majority were fish. Paquet plans to follow up with another study in three or four years.

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