Harbor seal (Phoca vitulina richardii) populations in the inland waters of Washington and British Columbia are at or near carrying capacity. Stranded pups often are collected and admitted to rehabilitation centers, and then released when they reach a weight of 22 kg and meet a variety of preestablished health and release conditions. While rehabilitation is common practice, it is unclear if rehabilitated seal pups behave like wild weaned pups. Using satellite transmitters, we compared movement patterns of 10 rehabilitated pups with 10 wild weaned pups. When released, rehabilitated seals were longer and heavier than wild pups, while wild pups had a larger mean axillary girth. No clinically different blood parameters were detected. On average, rehabilitated harbor seal pups traveled nearly twice as far cumulatively, almost three times as far daily, and dispersed over three times as far from the release site compared to wild weaned seals. Additionally, wild harbor seals transmitted nearly twice as long as did rehabilitated seals. These patterns suggest that learned behavior during the brief 3–4 wk nursing period likely enables wild harbor seal pups to move less daily and remain closer to their weaning site than rehabilitated pups.
Vertically transmitted nematodes can be a significant case of morbidity and mortality in some pinnipeds. Examples include the transmammary transmission the infective L3 of Uncinaria lucasi in Northern fur seals (Callorhinus ursinus) and Uncinaria spp. in California sea lions (Zalophus californianus) and in Juan Fernandez fur seals (Arctocephalus philippi).
To the best of our knowledge, transmammary or transplacental transmission of nematodes has never been documented in harbor seals (Phoca vitulina). Four deceased and six live stranded harbor seal pups collected between June and August 2012 in San Juan County, Washington, were studied for evidence of vertical transmission of internal parasites. Samples evaluated included lungs, liver, and gastrointestinal tracts collected from pre-weaned pups at necropsy and fecal samples from live stranded pups in rehabilitation. Tissue samples were evaluated by rinsing through a sieve and resultant material was examined for evidence of parasites. Fecal samples were examined via centrifugal float using zinc sulfate solution. Samples from the live pups showed no evidence of parasite infestation or shedding. However, a single necropsy sample revealed a developing adult male Phocanema decipiens nematode in the gastrointestinal tract of a three-day-old male harbor seal pup, suggesting vertical transmission of this parasite can occur in harbor seals. Infestation with P. decipiens has been widely reported in adult harbor seals in the Salish Sea but this is the first known documentation of infestation in a pre-weaned pup. The prevalence of P. decipiens in pre-weaned pups should be further studied, as should the potential clinical significance of this infection in harbor seal pups.
Tissue perforation and penetration by dorsal fin spines of spotted ratfish (Hydrolagus colliei) were responsible for the death of seven harbor seals (Phoca vitulina) in Washington State (USA) between 2006 and 2011. In six animals, necropsy revealed spines or spine parts that had perforated the esophagus or stomach and migrated into vital tissues, resulting in hemothorax, pneumothorax, pleuritis, and peritonitis. In a seventh case, a ratfish spine was recovered from the mouth of a harbor seal euthanized due to clinical symptoms of encephalitis. Gross examination revealed an abscess within the left cerebrum, which was attributed to direct extension of inflammatory infiltrate associated with the ratfish spine. Between 2009 and 2011, spotted ratfish spines were also recovered from the head or neck region of three Steller sea lions (Eumetopias jubatus) and one California sea lion (Zalophus californianus). Ratfish-related trauma appears to be a novel mortality factor for harbor seals in Washington State and could be related to increased ratfish abundance and a shifting prey base for harbor seals.