Abstract
Australian fur seals breed on thirteen islands located in the Bass Strait, Australia. Land access to these islands is restricted, minimising human presence but boat access is still permissible with limitations on approach distances. Thirty-two controlled noise exposure experiments were conducted on breeding Australian fur seals to determine their behavioural response to controlled in-air motor boat noise on Kanowna Island (39°10′S, 146°18′E). Our results show there were significant differences in the seals' behaviour at low (64–70 dB) versus high (75–85 dB) sound levels, with seals orientating themselves towards or physically moving away from the louder boat noise at three different sound levels. Furthermore, seals responded more aggressively with one another and were more alert when they heard louder boat noise. Australian fur seals demonstrated plasticity in their vocal responses to boat noise with calls being significantly different between the various sound intensities and barks tending to get faster as the boat noise got louder. These results suggest that Australian fur seals on Kanowna Island show behavioural disturbance to high level boat noise. Consequently, it is recommended that an appropriate level of received boat sound emissions at breeding fur seal colonies be below 74 dB and that these findings be taken into account when evaluating appropriate approach distances and speed limits for boats.
Highlights
Anthropogenic disturbance is a significant catalyst of environmental change, with potentially important implications for individuals and populations [1]
Study site The study examined the behavioural response of Australian fur seals on Kanowna Island (39u109S, 146u189E), Bass Strait, Australia, during the November–December 2008 breeding season over a two week period
Individual behaviours (Table 2) were compared among three phases using generalised mixed model (GLMM) analysis, with 112 individual seals used in this analysis
Summary
Anthropogenic disturbance is a significant catalyst of environmental change, with potentially important implications for individuals and populations [1]. Australian fur seals, (Arctocephalus pusillus doriferus), are endemic to Australia and breed on thirteen islands located in south-eastern Bass Strait [5]. These breeding islands provide areas where seals give birth, mate and raise their young away from potential threats of terrestrial predators, including humans. Male Australian fur seals compete aggressively to establish and maintain territories. At this time, females give birth, mate shortly thereafter and alternate between feeding out at sea and suckling their young on land [6]. The use of sight, smell and hearing are critically important to the species’ ecological and breeding strategy
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