Juvenile Steller sea lion dive behavior following temporary captivity

Abstract

Wild-caught juvenile Steller sea lions Eumetopias jubatus (n = 21) were maintained in temporary captivity for up to 12 wk to investigate health, disease, nutrition and behavior. We assessed the effects of captivity on post-release dive behavior and movement of each animal using externally mounted satellite data recorders. Based on a 74.1 ± 9.6 (SE) d tag transmission period, the mean dive depth (26.2 ± 4.0 [SE] m), dive duration (1.4 ± 0.1 [SE] min), dive rate (10.1 ± 0.5 [SE] dives h 1), trip duration (10.8 ± 0.7 [SE] h), haul-out duration (11.3 ± 0.9 [SE] h) and time wet (46.9 ± 2.6 [SE]%) were within the range of previously published values. Movement (190.0 ± 31.9 [SE] km) between haul-outs and rookeries during the tracking period was also typical of juvenile Steller sea lions in Alaska. This study indicates that temporary captivity has little or no detrimental effect on dive performance or movement in the tracking period following release.

In cold blood: evidence of Pacific sleeper shark (Somniosus pacificus) predation on Steller sea lions (Eumetopias jubatus) in the Gulf of Alaska

“…Previously published control studies with animals monitored during temporary captivity (21-71 d) and tracked for a mean postrelease period of 86 d (SD 55; range: 10-242 d; n=35) for implanted animals and of 76 d (SD 54;n=30) for nonimplanted animals-with all animals having conventional satellite transmitters externally attached after their release (Wildlife Computers SDRT-16 and SPLASH-5 tags)-confirmed that 1) implant surgery results in mild to moderate wound healing responses and temporary elevation of white cell counts and haptoglobin concentrations, with full physiological recovery within 45 d following surgery; 2) tags and surgery result in zero mortality to 45 d; 3) postrelease foraging and ranging behavior does not differ between implanted and nonimplanted animals or between temporarily captive and free-ranging animals; and 4) the cumulative survival of animals over the ages of 14-60 months was 0.415 (95% confidence intervals [CI]=0.26-0.63), compared with 0.413 (95% CI=0.27-0.55) for mark-resight studies based on hot iron branding conducted by the National Marine Fisheries Service, providing no evidence of any effects of LHX tags or implant surgery on survival to the age of 5 years (Mellish et al, 2006(Mellish et al, , 2007Thomton et al, 2008;Petrauskas et al, 2008;Walker et al, 2009;Horning and Mellish, 2012).…”

Spatially explicit detection of predation on individual pinnipeds from implanted post-mortem satellite data transmitters

“…Combined with the onset of transmissions at the very next opportunity, by tags floating in water, this suggests 3 cases of acute death at sea by major trauma. Two of these 3 animals still carried an externally attached satellite data transmitter and exhibited diving behavior comparable to previously monitored, implanted animals (Mellish et al 2007, Thomton et al 2008, hours before death.…”

“…From this previously observed return to baseline values in all monitored parameters, a 45 d post-surgery survival criterion was established for inclusion of animals in the study. Post-release tracking data revealed no significant differences in diving and ranging behavior between implanted and non-implanted animals (Mellish et al 2007, Thomton et al 2008. Minimum confirmed survival after surgery for the 21 implanted animals was 334 ± 72 d (mean ± SEM, range 68 to 1325).…”

“…Previously published control studies have shown that implant procedures are well tolerated and do not alter short term post-release behavior and survival (Mellish et al 2007, Petrauskas et al 2008, Thomton et al 2008. Within the constraints of a very low sample size, a comparison of preliminary estimates of survival rates derived from LHX tag returns, to rates derived from brand re-sight studies conducted by the NMML (L. Fritz pers.…”

“…All animals were monitored for health and clinical chemistry indicators during captivity, and had to meet previously established rigorous health criteria prior to release (Mellish et al 2006(Mellish et al , 2007. All animals were monitored following their release via externally attached, satellite-linked data transmitters (Mellish et al 2007, Thomton et al 2008, and through opportunistic re-sighting of hot-iron brand markings (N = 20) or plastic flipper tags (N = 1). Captive monitoring indicated non-significant white cell elevations, as well as significant increases in lympho-and monocytes, globulins, and haptoglobin concentrations after implant surgeries.…”