4/17/2023 0 Comments Are otters predators“Only a dozen or so small colonies survived,” Estes tells us. However, the sea otter’s thick, rich pelt also made it a major target for hunters who, by the 1900s, had brought the animal close to extinction. They help kelp forests to flourish by keeping sea urchin numbers under control. A member of the weasel family, the sea otter ( Enhydra lutris) keeps warm in the water because it possesses the densest fur in the animal kingdom – about 850,000 to a million hairs per square inch. As explorers opened up the far north two centuries ago, hunters pushed deeper into the Aleutians in pursuit of the pelts of the sea otters that thrived there in their hundreds of thousands. This isolation has not put the islands beyond the harmful influence of humans, however. “No place in the modern world is much wilder or more remote than the Aleutians,” he says. This top-down picture – with predators influencing the health of plants – is depicted in enthralling detail in his newly published Serendipity: An Ecologist’s Quest to Understand Nature (University of California Press).Įstes has spent most of his working life in the Aleutian Islands, which stretch across the North Pacific Ocean from Alaska to the coast of Kamchatka in eastern Russia. Top-down forcing – or trophic cascades – looks at the problem in the reverse direction, with a perfect example being provided by the work of James Estes, an American marine biologist who has studied wildlife in the north Pacific Ocean for the past 45 years and has revealed the astonishing manner in which terrestrial and sea predators can change land and marine environments. An example of this approach is provided by scientists who study how reductions in Arctic sea ice might reduce levels of algae (which forms on the underside of sea ice) and which might then affect the creatures that consume alga: the plankton, fish and seals further up the food chain. This view of nature – looking down from the top – contrasts with previous attempts to understand food chains from changes that affect their bottom rungs to see how animals and predators at higher levels are affected. More to the point, as human activities impact more and more on wildlife, we are changing trophic cascades with profound and unexpected consequences. Nevertheless, the concept of trophic cascades – as these ladders of interacting predator and prey populations are now known – is recognised today as being a powerful and important force in shaping the natural history of our planet. Huxley was almost certainly being facetious in outlining his maids‑to-empire chain. Around islands that lacked sea otters, urchins had increased in size and in numbers with devastating consequences Thus old maids would provide the perfect setting for ensuring plenty of clover and therefore healthy cattle and good roast beef to feed our troops and thus ensure the prosperity of the British Empire. Cattle graze on clover and cattle means beef. They kept cats, Huxley argued, and those pets would ensure neighbouring fields would be low in mice, high in bees and rich in clover.Īnd that in turn would have powerful consequences for the British Empire, Huxley added. It was an idea that took the fancy of Darwin’s chief disciple, the biologist Thomas Huxley who extended this cat-clover cascade in 1892 to include old maids.
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