Variability in haul-out behaviour by male Australian sea lions Neophoca cinerea in the Perth metropolitan area, Western Australia

Sk Osterrieder,C Salgado Kent,Rw Robinson

doi:10.3354/esr00690

Abstract

Pinnipeds spend significant time hauled out, and their haul-out behaviour can be dependent on environment and life stage. In Western Australia, male Australian sea lions Neo - phoca cinerea haul out on Perth metropolitan islands, with numbers peaking during aseasonal (~17.4 mo in duration), non-breeding periods. Little is known about daily haul-out patterns and their association with environmental conditions. Such detail is necessary to accurately monitor behavioural patterns and local abundance, ultimately improving long-term conservation manage- ment, particularly where, due to lack of availability, typical pup counts are infeasible. Hourly counts of N. cinerea were conducted from 08:00 to 16:00 h on Seal and Carnac Islands for 166 d over 2 yr, including 2 peak periods. Generalised additive models were used to determine effects of temporal and environmental factors on N. cinerea haul-out numbers. On Seal Island, numbers increased significantly throughout the day during both peak periods, but only did so in the second peak on Carnac. During non-peak periods there were no significant daytime changes. Despite high day-to-day variation, a greater and more stable number of N. cinerea hauled out on the sig- nificantly smaller beach of Seal Island during 1 peak. Overall, numbers hauled out were associ- ated with temperature and tidal height, but not wind speed. Relative percentages of age classes hauled out also varied with time of breeding cycle. Due to high variability in haul-out behaviour in space and time, and its association with environmental conditions, we conclude that counts for monitoring relative abundance in management decisions should be conducted systematically, using robust survey designs with relatively large sample sizes.

Highlights

Hauling out is a behaviour displayed by pinnipeds where animals temporarily leave the water to spend time on land between periods of activity
Diurnal haul-out patterns can vary between locations (Cunningham et al 2009), a trait observed in South American sea lions Otaria flavescens (Rosas et al 1994, Sepúlveda et al 2001, 2012)
The final Generalised additive models (GAM) selected which produced the most parsimonious model followed the form: log(μi) = α + β1 × TimeSinceSunrisei + β2(Periodi × Locationi) + β3 × Tidei + s(Temperaturei) + ei where: ei = Time + εi with μ being the number of N. cinerea observed at count i, α being the intercept, β the corrections of the slope for each covariate at count i, s the smoothing function, and ei consisting of the correlation structure indicated by the Time + noise ε

Summary

Introduction

Hauling out is a behaviour displayed by pinnipeds where animals temporarily leave the water to spend time on land between periods of activity. Hauling out onto land is important for pinnipeds during specific periods of their life cycle, such as breeding and moulting, but most pinniped species haul out for other reasons. They may travel considerable distances to foraging grounds and may forage at their aerobic dive limits Within a population of the same species, age and sex, as well as timing within the breeding, pupping or moulting cycles, can influence haul-out patterns (Thompson et al 1989, Reder et al 2003, Bengtson & Cameron 2004). Diurnal haul-out patterns can vary between locations (Cunningham et al 2009), a trait observed in South American sea lions Otaria flavescens (Rosas et al 1994, Sepúlveda et al 2001, 2012)

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