Factors influencing prey capture success and foraging efficiency in little penguins (Eudyptula minor)

The volatility of the marine environment makes it a difficult habitat to forage in. Being the smallest of the penguin species, with the most restricted foraging range of any seabird, little penguins (Eudyptula minor) are particularly sensitive to fluctuations in the distribution and abundance of prey controlled by local ocean conditions. Previous studies have investigated foraging success and efficiency (these metrics being measured in various ways) in relation to foraging behaviour, yet there is an absence of information on the intrinsic morphological factors and extrinsic environmental factors influencing these foraging metrics. In the present study 285 individuals were instrumented with GPS, dive behaviour loggers and accelerometers across eight years, from two colonies in south-eastern Australia (London Bridge and Gabo Island). Results displayed a lack of influence of any morphometric parameters on foraging success or efficiency at either site. Mean dive depth (m) and its association with prey type were shown to have a positive influence, foraging success and efficiency increasing with depth and behaviours reflective of the favourable prey type being hunted. Wind speed and direction, as measured by U vector and wave period (s) also revealed the benefits of onshore movement, suggesting time and energy spent finding productive prey patches is decreased as prey is being brought closer. Results suggest that due to the impact of local conditions on foraging outcomes and the relationship between prey type and dive depth, global changes in conditions may alter the distribution of prey both vertically and horizontally within little penguin foraging areas, with the potential to impact foraging abilities of little penguins and other marine predators in the future.