The Physical and Behavioral Effects of Enrichment in Rehabilitating Eastern Pacific Harbor Seals (Phoca vitulina richardii)

There is empirical support for the efficacy of enrichment in improving health and well-being in laboratory, agricultural, and zoo settings. However, little research has been done on the possible value of enrichment in facilitating successful reintroduction of rescued animals. The Marine Mammal Center in Sausalito, CA, cares for and then reintroduces Eastern Pacific harbor seal pups (Phoca vitulina richardii) that have become stranded due to maternal separation or abandonment. Currently, attention to the seals is limited to veterinary and feeding protocols, with no formal interventions aimed at species-typical behaviors or psychological wellbeing. In the current study, four rehabilitation enclosures were be designated as enrichment or control. Behavioral data were collected on 32 pups in these pools throughout the stranding season (April – July, 2017). In three enrichment sessions/day pups were exposed to apparatus that elicited species-typical behaviors related to foraging and exploration (e.g., diving, tactile investigation, etc.). Stereotypical behaviors (e.g. flipper chewing, repetitive swimming), stress levels as measured by fecal glucocorticoid metabolites (FGM), time spent underwater, blood oxygen storage capacity, and number of days to independently forage (free-feed) were the dependent variables. With these data I tested five hypotheses: compared to control pups, pups in the enrichment condition will: display fewer stereotypical behaviors (H1); have lower stress levels as measured by fecal cortisol (H2); and progress faster toward independent feeding (H4). I also predicted a positive relationship between enrichment and oxygen storage capacity that would be mediated by time spent underwater (H3). Finally, I tested the hypothesis that the degree to which pups interacted with the enrichment devices would be negatively correlated with time in rehabilitation (H5) such that pups who interacted less with enrichment took longer to free feed. Although I found no statistical support for H2 or H4, I found tentative support for H1 and H5 with p values approaching significance in both cases. Regarding H3, time spent underwater did not mediate the effect of exposure to enrichment and time spent underwater, however, enriched seals did spend significantly more time underwater than the control seals. This study extends the literature on enrichment to rehabilitation settings, and has implications for improving the welfare of rehabilitating seal pups and reducing the costs of rehabilitation.