November 8 2009
Why do whales beach themselves?
The Scientific American article “Why do whales beach themselves?” published on June 1, 2009, bring the polemic and controversial reasons about the phenomenon observed in the last years when more than Fifty-five false killer whales were stranded on a South African beach over the weekend. The scientists still do not fully understand why mass stranding happen, and if we should be worried about this event. Whales are the largest marine mammals in the world — the smallest species weigh in at several tons. When whales beach themselves, they can die simply from the crushing weight of their own bodies or from overheating due to their blubber, which is needed for insulation in cold ocean waters.
Stranding are of several types, said Susan Parks, a research associate in the Environmental Acoustics program in the Applied Research Laboratory at Penn State. Individual stranding often are caused by isolated incidents such as sickness, injury, or old age Said Parks, "Entanglement in fishing gear is one of the leading causes of mortality for marine mammals, many of which wash up on shore dead or injured." The tide carries these whales into shallow water, depositing them on the beach. Then there are multiple-species stranding, explained Parks. "This occurs when different species of marine mammals beach themselves at the same time and place, suggesting that they all died from the same cause," she said.
Scientists have been researching possible causes of this phenomenon. One explanation involves the whale "pod" social structure. For instance, whales that travel in pods use a "strength in numbers" survival strategy, but this can backfire when the dominant whale runs aground. According to Parks, "The rest of the pod may follow a disoriented or sick whale onto shore." Another theory is that pods may venture too close to the beach when hunting...