S. E. Fire, Z. Wang, M. Berman, G. W. Langlois, S. L. Morton, E. Sekula-Wood, & C. R. Benitez-Nelson (2010). Trophic Transfer of the Harmful Algal Toxin Domoic Acid as a Cause of Death in a Minke Whale (Balaenoptera acutorostrata) Stranding in Southern California. Aquatic Mammals 36(4): 342-350

Unusually high concentrations of the neurotoxin domoic acid (DA) were detected in a minke whale (Balaenoptera acutorostrata) carcass recovered during a severe harmful algal bloom (HAB), which occurred in southern California in April 2007. Cell fragments of the toxigenic diatom Pseudonitzschia australis were observed in whale gastric fluid and feces, corresponding to a dominance of Pseudonitzschia spp. in the phytoplankton com-munity at the time of stranding. A high abundance of otoliths from a prominent DA vector, the northern anchovy (Engraulis mordax), were recovered in whale stomach contents, indicating trophic transfer of DA via the food web. Whale feces contained 258 μg DA per gram sample, exceeding DA concentrations reported for any marine mammal. DA intoxication was identified as the cause of mortality of this animal, expanding on the limited understanding of the impacts of DA-producing HABs on large whales.

O. A. Lee, F. Gelwick, & R. W. Davis (2010). Summer Foraging Tactics in Sea Otters (Enhydra lutris): Maintaining Foraging Efficiencies in a Stable Population in Alaska. Aquatic Mammals 36(4): 351-364

Foraging specializations in large populations can reduce intraspecific competition for food. When individuals do not specialize on particular prey species, resource partitioning might occur as different search strategies at the sex and age group levels. This study focused on the foraging tactics of sea otters in a stable population in Alaska by testing cost-minimizing, energy-maximizing, and efficiency-maximizing models. Canonical Correspondence Analysis (CCA) was used to analyze the boat-based behavioral observations of 119 foraging bouts for adult males and females, females with pups, and juveniles. Observations were conducted during one summer breeding season. A foraging efficiency ratio was calculated using the gain variable—estimated mean energy values from captured prey—and the cost variables—inter-dive distances traveled and dive depths. Foraging efficiency ratios were not significantly different between all adults, including females with pups. Juveniles had significantly lower foraging efficiency ratios related to low mean energy gains and a higher proportion of unsuccessful dives. A cost-minimizing strategy was identified in females with pups that minimized travel costs and obtained low prey energy per dive. Adult males and females without pups used an energy-maximizing strategy of high travel costs and high prey energy gains per dive. The ability of adult females to change foraging strategies with the demands of raising a pup indicate female adult sea otters can have flexible foraging strategies while maintaining high foraging efficiencies.

H. Frouin, L. Ménard, L. Measures, P. Brousseau, & M. Fournier (2010). T Lymphocyte-Proliferative Responses of a Grey Seal (Halichoerus grypus) Exposed to Heavy Metals and PCBs in Vitro. Aquatic Mammals 36(4): 365-371

This study investigated in vitro the effects of methylmercury chloride (CH3HgCl), zinc chloride (ZnCl2), cadmium chloride (CdCl2), lead acetate (Pb(C2H3O2)2), and PCBs (Aroclor mixtures) on the proliferation of T lymphocytes from the thymus, lymph node, and blood from one female grey seal (Halichoerus grypus) juvenile. After exposure to heavy metals, a dose-response curve was observed with a decrease in proliferation of both T lymphocytes from blood and the lymph node. Exposure to Aroclor mixtures led to a mostly reduced proliferation of thymocytes and T lymphocytes from the lymph node and blood. Lymph node cells seem less sensitive to heavy metals than peripheral blood lymphocytes. Lymph node lymphocytes are more sensitive to PCBs than peripheral blood lymphocytes but less than thymocytes. These results suggest that the sensitivity of T lymphocytes from one grey seal to contaminants may be due to inherent tissue/matrix differences in the sensitivity of these cells to contaminants; however, an individual response cannot be excluded in the present case. That is, samples from a single individual are not extrapolated to the species as a whole in this paper but discussed relative to exposure response by tissues.

The Shannon Estuary is home to Ireland’s only known resident population of bottlenose dolphins (Tursiops truncatus) and is designated as a candidate Special Area of Conservation (cSAC) for this species. Proper conservation management of these dolphins requires an understanding of the social structure of this population. Four years of photo-identification data (2005 to 2009, excluding 2007) were used to construct sociograms that complement a cluster analysis of individually marked dolphins and their associates. The results found little evidence of social stability or group fidelity for this study’s dolphin population. Analysis of dolphins observed in consecutive years showed that the probability of group members encountering an individual dolphin in the second year did not depart from a random model. The social parameters for this resident population seem to be typical for this species. Bottlenose dolphins are found to exhibit a highly fluid, dynamic social structure within which individuals change their composition and associates regularly. These dolphins in the Shannon Estuary appear to live in a fission-fusion based society.

Short Notes

R. L. Gentry (2010). Marine Mammal Research Then and Now. Aquatic Mammals 36(4): 388-399

K. C. Balcomb III (2010). Whales in a Changing World. Aquatic Mammals 36(4): 400-408

D. Fertl (2010). The Question of Animal Culture. K. N. Laland & B. G. Galef. Aquatic Mammals 36(4): 409

William Eugene Evans. (2010). Aquatic Mammals 36(4): 411-419