Keystone Species

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Keystone species are species central to an ecosystem, species upon which nearly all other species depend. Several keystone species have been identified in the wild, but it is not easy to predict which species will be keystone because the connections between species in food webs are often complex and obscure.


The populations of big-cat prey including the red coati (Nasua nasua), the agouti (Dasyprocta variegata), and the paca (Agouti paca) are about ten times higher than on Cocha Cashu, Peru, where big cats still live. However, this increase may result from natural population variability rather than the lack of jaguars and pumas. The extreme removal of herbivores and frugivorous mammals would drastically affect forest regeneration, altering tree species composition, but the effects of modest changes in densities are less clear.
The sea otter (Enhydra lutris) is a keystone predator par excellence (Duggins 1980). A population of around 200,000 once thrived on the kelp beds lying close to shore from northern Japan, through Alaska, to southern California and Mexico. In 1741, Vitus Bering, the Danish explorer, reported seeing great numbers of sea otters on his voyage among the islands of the Bering Sea and the North Pacific Ocean. Some furs were taken back to Russia and soon this new commodity was highly prized for coats. Hunting began. In 1857, Russia sold Alaska to the United States for $7,200,000. This cost was recouped in forty years by selling sea otter pelts. In 1885 alone, 118,000 sea otter pelts were sold. By 1910, the sea otter was close to extinction, with a world-wide population of fewer than 2,000. ...
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