Distinguishing the Impacts of Inadequate Prey and Vessel Traffic on an Endangered Killer Whale (Orcinus orca) Population

Managing endangered species often involves evaluating the relative impacts of multiple anthropogenic and ecological pressures. This challenge is particularly formidable for cetaceans, which spend the majority of their time underwater. Noninvasive physiological approaches can be especially informative in this regard. We used a combination of fecal thyroid (T3) and glucocorticoid (GC) hormone measures to assess two threats influencing the endangered southern resident killer whales (SRKW; Orcinus orca) that frequent the inland waters of British Columbia, Canada and Washington, U.S.A. Glucocorticoids increase in response to nutritional and psychological stress, whereas thyroid hormone declines in response to nutritional stress but is unaffected by psychological stress. The inadequate prey hypothesis argues that the killer whales have become prey limited due to reductions of their dominant prey, Chinook salmon (Oncorhynchus tshawytscha). The vessel impact hypothesis argues that high numbers of vessels in close proximity to the whales cause disturbance via psychological stress and/or impaired foraging ability. The GC and T3 measures supported the inadequate prey hypothesis. In particular, GC concentrations were negatively correlated with short-term changes in prey availability. Whereas, T3 concentrations varied by date and year in a manner that corresponded with more long-term prey availability. Physiological correlations with prey overshadowed any impacts of vessels since GCs were lowest during the peak in vessel abundance, which also coincided with the peak in salmon availability. Our results suggest that identification and recovery of strategic salmon populations in the SRKW diet are important to effectively promote SRKW recovery

The dual functions of sea urchin gonads are reflected in the temporal variations of their biochemistry

Fatty acid analyses are emerging as a powerful technique to probe trophic interactions between organisms. In this paper, the application of both this procedure and gonad index (GI) determination on two populations (intertidal and subtidal) of the echinoid Psammechinus miliaris is reported. The investigation spanned the 3-month spawning period of Scottish west coast populations. In both populations a progressive decrease in the GI was found, coupled with an increasing maturity stage (from mature to spent). Sexual maturation and decrease in GI was synchronous between the two populations. In conjunction, there were distinct changes in gonad biochemistry. Differences in the fatty acid composition of the gonad reflected the changes in sexual maturation. Mature males and females had significant differences in the fatty acid composition of their gonads, whereas post-spawned individuals showed no gender differences. Male urchins had higher levels of polyunsaturated fatty acids (PUFAs) compared to females, and there was a dramatic reduction in the fatty acids 22:6(n−3) and 20:5(n−3) with increasing maturity stage. Using multivariate statistical techniques, these changes in the fatty acid composition of the sea urchin gonad were linked to habitat related diet differences combined with gender differences. These changes in the fatty acid signatures clearly reflect the dual function of the gonad as both a nutrient store and a reproductive organ

Social foraging European shags: GPS tracking reveals birds from neighbouring colonies have shared foraging grounds

Developments in tracking technologies have enhanced our understanding of the behaviours of many seabird species. However few studies have examined the social aspects of seabird foraging behaviour, despite the effect this might have on the distribution of foraging areas and the differences that might arise between colonies. Here we use bird-borne GPS and behavioural observation to study the social foraging behaviour and habitat use of breeding shags from three breeding colonies in the Isles of Scilly, UK. Thirteen breeding shags from three colonies (six at two colonies and a single bird from another) were tracked between 2010 and 2012 and related to observations of conspecific foraging aggregations (2013-2014). Tracked shags had short foraging ranges (1.74 ± 1.6 km) mostly travelling to shallow waters between the islands and observations revealed that many shags foraged in large social groups that were consistent in time and space. There were also no clear differences in foraging distributions among colonies—birds shared similar foraging grounds. Our finding provides important insight into the use of social information among foraging seabirds and how this may lead to shared foraging areas, as well as space partitioning

Shallow divers, deep waters, and the rise of behavioural stochasticity

International audienceLittle penguins (Eudyptula minor) have oneof the widest geographic distributions among penguins,exposing them to variable ecological constraints acrosstheir range, which in turn can affect their foraging behaviour.Presumably, behavioural flexibility exists to allowanimals to adapt to prevailing environmental conditionsthroughout their foraging range. This study examinedwhether complexity in the temporal organization of foragingsequences corresponds to characteristics of the foragingarea across four colonies geographically distributed alongthe entire species’ range. Complexity and fractal scalingin spatiotemporal patterns of foraging behaviour havebeen theoretically linked to foraging efficiency in heterogeneousenvironments. Using fractal time series methods(detrended fluctuation analysis), we found that foragingcomplexity along a stochastic–deterministic gradient was associated with bathymetry in local foraging areas; littlepenguins foraging in deeper waters produced more stochastic/less deterministic foraging sequences than thoseforaging in shallower waters. Corresponding data on fledgingsuccess suggest that little penguins foraging in deeperwaters also experienced reduced reproductive success. Aprincipal component analysis further showed that our fractalscaling index, which specifically measured the degree towhich sequences are long-range dependent (a deterministicphenomenon), correlated positively with foraging efficiency(prey encounter per unit time) and negatively withforaging effort (total time underwater). Our statistical modelsshowed that production of complex foraging sequenceswith high degrees of stochasticity appears to be energyintensive. However, we could not determine which strategywould have maximized foraging success, a variable wecould not measure, under the conditions observed. We proposethat increasing stochastic elements in foraging behaviourmay be necessary under challenging environmentalconditions, but it may not be sufficient to match fitnessgains attained under more favourable conditions