Survival and mortality
This chapter discusses age-structure in Eurasian and North American river otters. Otters have short life expectancy, with mortality increasing with age. Sea otter is a long-lived exception. Causes of death are enumerated, including predation, intra-specific mortality, and various human activities. Starvation appears to be the most important cause. The index of body-condition K is formulated. Various kinds of pollutants and their effects are described, including insecticides, PCBs, and mercury. There is little evidence that pollution substantially affects present-day populations. Although predation in most species is insignificant, predation of sea otters by sharks and killer whales has caused large population declines; part of a ‘megafauna collapse’.
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