Routine stress from parasitism, minor injuries, environmental factors, and altered nutritional status have surprisingly little effect on pregnancy, once implantation has occurred and the developing fetus is securely established in the uterus. The exception is severe trauma occurring near the end of gestation, which may induce premature parturition (Moberg, 1985). Pregnant sea otters in a rehabilitation center are at special risk from the potential toxicity, organ damage, and thermoregulatory problems associated with crude oil contamination, and by the combined stress of capture and medical treatment (see Chapter 1). During an oil spill, provisions must be made at the rehabilitation center for the treatment, husbandry, and housing of pregnant marine mammals and newborn pups. This chapter addresses the special needs and problems of these animals, with particular emphasis on the pregnant sea otter.
In the wild, female sea otters often congregate in favorite feeding and resting areas, especially during late gestation and for several weeks after the pups are born. An oil spill that moves through such an area may contaminate large numbers of females and their offspring. This situation occurred during the Exxon Valdezoil spill (EVOS) when the spill engulfed Green Island in late March. Because peak pupping occurs in May (Reidman and Estes, 1990) and Green Island (Prince William Sound) is used by many female otters as a pupping area, the rehabilitation center in Valdez received a disproportionate number of heavily oiled, pregnant sea otters (Williams and Davis, 1990).
A similar risk exists for other species of marine mammals. The birth lairs of ice-breeding seals and polar bears are vulnerable to contamination by coastal spills. Other species of phocid seals, sea lions, and fur seals give birth on rookeries during the spring. If a spill occurs near a pupping rookery, large numbers of pregnant females and newborn pups may become oiled. Such an incident occurred in 1991 when the Sanko Harvest oil spill contaminated hundreds of fur seal (Arctocephalus fosteri) pups in southwest Australia (see Chapter 15).
Many newborn pinnipeds, which rely on lanugo (prenatal fur) and have a high metabolic rate to maintain their core temperature, are especially susceptible to hypothermia if they become oiled. In addition, petroleum hydrocarbons may accumulate in the blubber of pregnant females and be incorporated into the milk during lactation (Engelhardt, 1983). This will result in the ingestion of petroleum hydrocarbons by the pup long after the spill has dissipated.
