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