DDT in endangered Galapagos sea lions (Zalophus wollebaeki).

We characterize for the first time the presence of DDT and its metabolites in tropical Galapagos sea lions (Zalophus wolleabeki). ∑DDT concentrations in Galapagos sea lion pups sampled in 2005 and 2008 ranged from 16 to 3070 µg/kg lipid. Concentrations of ∑DDT in pups in 2008 averaged 525 µg/kg lipid and were 1.9 times higher than that (281 µg/kg lipid) detected in pups in 2005. These concentrations are lower than those reported in many pinnipeds elsewhere, comparable to those in Hawaiian monk seals, and higher than those in southern elephant seals. The health risk characterization showed that 1% of the male pups exceeded the p,p'-DDE toxic effect concentration associated with anti-androgenic effects reported in rats. The findings provide preliminary guidance on the relationship between DDT use and ecological impacts, serving as a reference point against which possible future impact of tropical DDT use can be assessed.

Rotavirus infections in Galapagos sea lions.

Group A rotaviruses infect and cause diarrhea in the young of a broad range of terrestrial mammals, but it is unknown, to our knowledge, whether they infect marine mammals. During February and March of 2002 and 2003, we collected 125 serum samples and 18 rectal swab samples from Galapagos sea lion pups (GSL, Zalophus wollebaeki), and 22 serum samples from Galapagos fur seal pups (GFS, Arctocephalus galapagoensis) from nine islands of the Galapagos archipelago, Ecuador. Sera were tested for antibodies (immunoglobulin G [IgG]) to rotavirus by an enzyme immunoassay using rhesus rotavirus as the capture antigen. In addition, rectal swabs were analyzed for the presence of rotavirus genomic double-stranded RNA by silver-stained polyacrylamide gel electrophoresis. Antibodies to rotavirus were detected in 27 GSL pups (22%) and five GFS pups (23%), and rotavirus RNA was detected in the fecal sample from one GSL pup (6%). These results provide the first evidence that rotavirus infections are prevalent at an early age in Galapagos sea lions and Galapagos fur seals.

Polychlorinated biphenyls and polybrominated diphenyl ethers in Galapagos sea lions (Zalophus wollebaeki).

Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) were measured in muscle-blubber biopsy samples from 21 Galapagos sea lion (Zalophus wollebaeki) pups that were live captured in the Galapagos Islands (Ecuador) using gas chromatography/high-resolution mass spectrometry. Only traces of PBDEs were detected in one male pup, whereas PCDDs and PCDFs were not detected in any sample. The total concentration of PCBs (ΣPCB) in the pups averaged 104 µg/kg lipid (range, 49-384 µg/kg). No statistically significant differences in ΣPCB were observed among the four study sites in the Galapagos Islands. Concentrations of PCB congeners in Galapagos sea lion pups were dominated by low-molecular-weight congeners. These results suggest that global transport is the main source for PCBs in Galapagos sea lions. The ΣPCB levels were below immunotoxic and endocrine-disruption thresholds in pinnipeds, suggesting a limited risk of adverse health effects. The present study indicates that Galapagos sea lions can serve as a useful sentinel of pollutants with a long-range transport capacity and that Galapagos Islands are not exempt from the threats of global pollutants despite its remote locale.

Tracing early stages of species differentiation: ecological, morphological and genetic divergence of Galápagos sea lion populations.

BACKGROUND: Oceans are high gene flow environments that are traditionally believed to hamper the build-up of genetic divergence. Despite this, divergence appears to occur occasionally at surprisingly small scales. The Galápagos archipelago provides an ideal opportunity to examine the evolutionary processes of local divergence in an isolated marine environment. Galápagos sea lions (Zalophus wollebaeki) are top predators in this unique setting and have an essentially unlimited dispersal capacity across the entire species range. In theory, this should oppose any genetic differentiation. RESULTS: We find significant ecological, morphological and genetic divergence between the western colonies and colonies from the central region of the archipelago that are exposed to different ecological conditions. Stable isotope analyses indicate that western animals use different food sources than those from the central area. This is likely due to niche partitioning with the second Galápagos eared seal species, the Galápagos fur seal (Arctocephalus galapagoensis) that exclusively dwells in the west. Stable isotope patterns correlate with significant differences in foraging-related skull morphology. Analyses of mitochondrial sequences as well as microsatellites reveal signs of initial genetic differentiation. CONCLUSION: Our results suggest a key role of intra- as well as inter-specific niche segregation in the evolution of genetic structure among populations of a highly mobile species under conditions of free movement. Given the monophyletic arrival of the sea lions on the archipelago, our study challenges the view that geographical barriers are strictly needed for the build-up of genetic divergence. The study further raises the interesting prospect that in social, colonially breeding mammals additional forces, such as social structure or feeding traditions, might bear on the genetic partitioning of populations.

Impacts of the Jessica oil spill on sea lion (Zalophus wollebaeki) populations.

Following the Jessica oil spill, a total of 79 oiled Galápagos sea lions (Zalophus wollebaeki) were recorded around the islands of San Cristóbal, Santa Fé, Isabela and Floreana. Almost half of these animals required washing and other treatment. One sea lion death and a high incidence of conjunctivitis and burns were detected during the period of the oil spill. Sea lion populations exhibited a tendency for decline in the first months following the spill at all three colonies monitored close to the grounding site on San Cristóbal. By comparison, declines of similar magnitude occurred at only one of six sea lion colonies monitored on islands more distant from the spill. However, no significant decreases in population numbers were detected for any colony in the year following the spill. Galápagos sea lion populations were partially recovering from the much more catastrophic impact of the 1997/98 El Niño.