Deborah A. Duffield

Telomeres as age markers in vertebrate molecular ecology

Chronological age is a fundamental and yet elusive variable in studies of many wild animals. Telomeres are nucleoprotein structures on the ends of chromosomes that change size throughout the life of many animals and because of this property have been advocated as a means to estimate age. In this review, we assess the existing and potential application of using telomeres for age estimation. We argue that there are conceptual and statistical inconsistencies in previous studies and that the basis for telomere change over time is not well understood and affected by several intrinsic and extrinsic process unrelated to chronological time. Furthermore, these processes are likely to vary spatially and temporally for animal populations. We conclude that the current data suggest telomeres should not be used for age estimation. If telomere‐based age estimation is to be used, more work in understanding variability in key processes affecting telomere dynamics and rigorous substantiation via blind testing is needed.

Use of high-performance liquid chromatography for the estimation of polychlorinated biphenyls and p,p-DDE residues in marine mammals

We present a screening technique for the detection of polychlorinated biphenyls (PCBs) and p,p-DDE residue levels in marine mammal blubber using high-performance liquid chromatography (HPLC). This method modifies the standard extraction and clean-up methods for organochlorines for use with HPLC and uses a method of chemical derivatization to separate and semi-quantify the two organochlorines with HPLC.

Increased harbor porpoise mortality in the Pacific Northwest, USA: understanding when higher levels may be normal

In 2006, a marked increase in harbor porpoise Phocoena phocoena strandings were reported in the Pacific Northwest of the USA, resulting in the declaration of an unusual mortality event (UME) for Washington and Oregon to facilitate investigation into potential causes. The UME was in place during all of 2006 and 2007, and a total of 114 porpoises stranded during this period. Responders examined 95 porpoises; of these, detailed necropsies were conducted on 75 animals. Here we review the findings related to this event and how these compared to the years immediately before and after the UME. Relatively equal numbers among sexes and age classes were represented, and mortalities were attributed to a variety of specific causes, most of which were categorized as trauma or infectious disease. Continued monitoring of strandings during 4 yr following the UME showed no decrease in occurrence. The lack of a single major cause of mortality or evidence of a significant change or event, combined with high levels of strandings over several post-UME years, demonstrated that this was not an actual mortality event but was likely the result of a combination of factors, including: (1) a growing population of harbor porpoises; (2) expansion of harbor porpoises into previously sparsely populated areas in Washingtons inland waters; and (3) a more well established stranding network that resulted in better reporting and response. This finding would not have been possible without the integrated response and investigation undertaken by the stranding network.

Activity Budgets and Prey Consumption of Sea Otters (Enhydra lutris kenyoni) in Washington

Northern sea otters (Enhydra lutris kenyoni) were extirpated from the Washington coast in the early 1900s. Reintroductions of sea otters from Amchitka Island, Alaska, occurred in 1969 and 1970. By 2005, 814 sea otters occupied a range from Destruction Island north to Makah Bay. The focus of this study was to investigate diurnal activity budgets and variability in prey consumption at four locations in the current Washington sea otter range to test hypotheses concerning population growth potential and local impact of sea otters on prey availability. Overall, sea otters primarily spent their daylight hours resting (62.3%), grooming (19.7%), and feeding (7.6%). These activities varied by location. Diet consisted predominantly of crabs, clams, and sea stars. In each study area, one main prey item comprised 33.4 to 64.4% of the total prey consumed; however, the main prey item differed among locations. Of the foraging dives observed, 81.4% were successful. Average dive duration was 35.6 s; however, this varied among locations as well. The study locations were utilized differently—some as resting sites and others as feeding sites. The low diurnal feeding activity found in this study indicates that food availability was high, suggesting that this Washington population of sea otters is currently below equilibrium density.

Paternal behaviour in a socially monogamous but sexually promiscuous passerine bird

We documented parental behaviour and paternity of eastern kingbirds (Tyrannus tyrannus) to test the predictions that paternal care would decline with increasing loss of paternity, increasing nesting density (a proxy for probability of paternity loss), male quality, and number of fertile females available in the population. Extra-pair young were found in 58% of 45 nests for which behaviour was recorded and a higher proportion of young were extra-pair as nesting density increased. Male feeding rate declined with increasing nesting density and male quality, but neither feeding rate nor a composite measure of paternal behaviour varied with number of fertile females or paternity. Although alternative explanations exist, one interpretation of the reduced paternal care at high nesting density was that it was a response to perceived threats of paternity loss. The ultimate basis for the lower paternal effort of higher quality males is unclear but we discuss several possible explanations.