Since the whales are not as available, orcas have had to change their diet to what is available. Second, orcas prefer to hunt whales, but whales have essentially disappeared in that area from human hunters. If a predator kills an otter, then it is eaten right away and can't wash up on shore.
However, the fact that dead otters are seldom found supports the predator hypothesis. Ongoing investigations have shown that predation is the most likely cause of the sea otter decline after all.įirst, there is a lack of dead sea otters washing up on Alaskan beaches which is not what you would expect from infections caused by pollution killing them off. Some experts suggested this could be explained by ocean currents, or other environmental factor, might have created uneven concentrations of pollutants along the coast. In some Alaskan locations the otter population declined greatly while other populations remained stable. Only predators that occurred in a large area, such as orcas (a large predatory whale), could cause the same effect, but they usually hunt larger prey.įinally, scientists believed the pollution hypothesis would also explain the uneven pattern of otter decline.
Environmental pollution usually affects an entire ecosystem instead of just one species. This indicated that whatever was affecting the otters was also affecting the other sea mammals. Also water samples taken in the area showed increased levels of chemicals that could decrease the otters' immune systems and indirectly result in their deaths.Īnother thing that pointed to pollution as the culprit was the decline of other sea mammals such as seals in the same areas. One reason pollution was more likely was because of the known pollution sources along the Alaskan coast such as oil rigs. One explanation was environmental pollution and the second was attacks by predators.Īt first it seemed as if the pollution was the most likely cause for the population decline. Experts began investigating and came up with two possible explanations. A few years ago some of the sea otter populations off of the Alaskan coast started to decline rapidly and raised several concerns because of their important role in the coastal ecosystem. Sea otters are a small mammal that lives in the waters along North America's west coast from California to Alaska.
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