Behavior, Movements, and Apparent Survival of Rehabilitated and Free-Ranging Harbor Seal Pups

Abstract

Post-release studies are essential to determine the efficacy of wildlife rehabilitation. Although an increasing number of Pacific harbor seal (Phoca vitulina richardsi) pups are admitted to rehabilitation centers, few studies have been conducted to monitor the behaviors and survival of rehabilitated pups released back into the wild. Our objectives were to compare diving behaviors, activity patterns, movements, and survival between rehabilitated pups (n = 29) and wild pups (n = 24). Pups were radiotracked for 5 months after release at Pebble Beach, California, during 1995, 1996, and 1998. Mean duration of dives (t 27 = 0.90, P = 0.37) and surface intervals (U = 52, P = 0.20) of rehabilitated pups did not differ from that of wild pups. Rehabilitated pups spent a greater proportion of their time in the water (t 18 = 2.12, P= 0.047) than did wild pups. Most pups traveled north from Pebble Beach, and movements were variable. Seal group (F 1 31 = 1.33, P= 0.26) or sex (F 1 31 = 0.22, P= 0.64) had no effect on maximum distance traveled. Survival curves between rehabilitated and wild pups were similar during 1995 (X 2 = 0.40, P> 0.05) and 1998 (X 2 = 1.34, P> 0.05), whereas rehabilitated pups had lower survival than wild pups during 1996 (X 2 = 3.94, P 0.05). In summary, the overall behavior, movement, and apparent survival of rehabilitated pups appeared similar to wild pups. Future studies should be conducted to assess the long-term survival of rehabilitated and free-ranging harbor seal pups.