Friday, 24 April 2015

Killer whales are stealing fishermen's catch to make extra calves

A population of orcas off the Crozet Islands in the Southern Ocean are taking advantage of toothfish caught on fishing lines to reproduce more successfully, reports Conservation 

Jason G. Goldman for Conservation Magazine, part of the Guardian Environment Network

Friday 24 April 2015 16.35 BST

Killer whales (Orcinus orca) didn’t get their name because they’re gentle herbivores. They are top marine predators, and as a species they feed on a variety of critters from fish to seabirds to marine mammals — including other whales. They are highly intelligent, long-lived animals, with complex social dynamics and traditions that vary from group to group. In other words, they have culture. And each family – orca societies are organized according to maternal relatedness – has its own customs and ways of surviving. Those customs are passed from individual to individual, much like human culture.

Over the past 50 years, even as whaling itself has been banned in most of the world, overfishing has impacted killer whale populations. That’s because the availability of prey is a critical factor in determining the long-term population viability of apex predators like killer whales. In other words, more food means more babies. Most females begin reproducing around age 10, and when resources are abundant, give birth to a calf approximately every 5-6 years until they go through menopause. Even after they stop reproducing, it’s thought that female orcas can live to more than 90 years of age.

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