Collaborations
Monitoring the status of the pinniped populations in California and Mexico and estimating colony size. The emphasis was on elephant seals, California sea lions, Steller sea lions, and Guadalupe fur seals. Principal collaborators were M. Lowry at Southwest, and also Rick Condit, David Aurioles, Juan-Pablo Gallo, and Ana Figueroa-Carranza.
Southern Elephant Seals in Patagonia
Studies were conducted on Southern sea lions and southern elephant seals in Patagonia, Argentina, with C. Campagna. Male sea lions guard females near them for mating. Peripheral males make group raids in the breeding area to steal females. Males with female are torn between fighting off the intruders and preventing their females from escaping. Southern elephant seals harems are smaller than those of northern elephant seals.
Persistent Organic Pollutants (POPs) in Pinnipeds
POPs are high in California sea lions and are associated with premature abortions and may affect reproduction in birds that feed on dead sea lions. The Santa Barbara Channel Oil Spill of 1969 soaked newly weaned elephant seal pups in crude oil but did not increase the mortality rate. Research conducted with Richard Peterson, Bob Brownell, Jr. Warm ocean waters associated with El Niños and decadal regimes reduced the foraging success of pregnant elephant seals and resulted in lower weaning weights of pups. Research conducted in collaboration with: Mike Bonnell, Lieberg-Clark, P., J. P. Giesy, K. Kannan, N. Kajiwara, S. Tanabe, C. Debier, K. Kannan, S. Tanabe, M.G. Ikonomou, T. de Teilesse, Y. LFarondelle, P.S. Ross, F. Gulland, D.P. Costa, J. Thome.
Marine Mammal Dive Behavior
My collaboration with Y. Naito began in 1986 and involved the attachment of instruments to the diving and migrating seals. This has led to many fundamental discoveries of the diving behavior of elephant seals. The success led to a memorandum of understanding between his institution and mine. This collaboration has involved many researchers from both countries and advanced significantly our understanding of the diving behavior of marine mammals, as well as the ecosystem in which they forage. For a summary of Y. Naito research, see “Historical Perspectives” (.pdf).
Collaborated with A. Hoelzel. Elephant seals lack genetic variability (Bonnell and Selander 1974; Hoelzel et al. 1993, 1999). Parentage cannot be distinguished with DNA fingerprinting. Inbreeding leads to loss of genes. Few males monopolize mating, and the longest-lived females produce most of the pups. The seals return to breed at same location which permits males to mate with daughters, adult females mate with sons, and brothers and sisters mate with each other. Much genetic variation was lost when the entire population was reduced less than 30 individuals in the late 1890s. As the population recovered, the survivors could only breed with each other.
White sharks prey on elephant seals at Año Nuevo from October to late December. We tracked their hunting strategies with automated listening stations and determined that some marked sharks return here to forage annually for six years, and that they patrol the area continuously searching for prey. The sharks depart the area in mid-winter and head off in the direction of the Hawaiian Islands. Since we did most of our behavioral research under the public eye of tourists visiting Año Nuevo State Park, we made our research findings available to docents, guides and rangers that could convey this information directly to visitors to enhance their viewing experience. We also published a book, The Natural History of Ano Nuevo, which we are now in the process of updating and reprinting.
Conservation Strategies
Several key articles on conservation and animal viewing spectacles were published with C Campagna and D. Guevara. The aim was to call attention to the increasing extinction rate of animals and the loss of their habitat, as well as the growing interest in viewing wild animals instead of killing them, as was the case not so long ago.
Stanford Medical Center
Doing magnetic resonance imaging (MRI) on seals? Yes, we did this at Stanford to determine changes in blood flow during diving. UC collaborators were Sheila Thornton and Dan Crocker. The juvenile elephant seal was placed in a PVC half-pipe and fitted with a diving helmet which could be flooded with water to force the seal to dive and then the water was evacuated to end the dive. The imaging showed a rapid contraction of the spleen and a simultaneous filling of the hepatic sinus, where red blood cells were meted out during the dive as needed. The seal take no mind of this and sleep during much of the experiment. Collaboration with Norbert Pelc is (now Emeritus Professor of Radiology at Stanford, Director of the Magnetic Resonance Imaging lab at Stanford in 2001 when this study was done.