Faecal testosterone concentrations and the acoustic behaviour of two captive male Australian fur seals

Seasonal changes in reproductive and acoustic behaviour are potentially affected by hormonal fluctuations; however, as it is difficult to routinely sample marine mammals, these associations are mostly inferred. Australian fur seals are vocal marine mammals that have a highly synchronous breeding season. The present study collected information on the testosterone concentration in faeces, vocalisations and behaviour of two captive male Australian fur seals to determine whether there are any associations between these variables. Positive associations were evident between the non-interactive agonistic behaviours (Head sway, Lay down and Head up) and an increase in calling rate of the bark calls in males. Barks were highest during August through to October, corresponding to the breeding period, while faecal testosterone levels peaked in September, coinciding with the high frequency in the calling rates of barks. Guttural threat calls were rarely heard throughout the year, but peaked in August. This call was not frequently heard but was associated with specific behaviours that were produced during more intense fighting interactions. This study presents preliminary information on the vocalisations, behaviour and hormone profiles for two captive Australian fur seals. Future studies with increased sample sizes from both wild and captive animals would clarify the intricate association between these factors.