In order to assess seasonal and spatial changes in diet, the δ 15 N and δ 13 C signatures of vibrissae from leopard seals Hydrurga leptonyx obtained from Prydz Bay, Eastern Antarctica, were compared with those of a captive seal on a known diet. Using the isotopic signatures of known prey, and those revealed by the assimilation rates of vibrissae, we constructed trophic models to estimate diet composition. Assuming that current diet was reflected only in the actively growing portion of the vibrissae, the latter were sectioned. Each section was then analysed independently. Two methods of analysis of the vibrissae isotopic data were compared in order to ascertain the best analytical approach to these data. A simple linear model and a von Bertalanffy growth model were used to estimate section age and vibrissae growth rates. The age predictions of the von Bertalanffy growth model allowed the existence of repeated seasonal oscillations in both δ 15 N and δ 13 C values. Temporal variations in stable isotope ratios consistent with changes in source of feeding (inshore vs. offshore) and prey types were identified in the Antarctic leopard seals, but not in the captive seal. This preliminary study has possible implications for the use of vibrissae to track dietary changes over time and may serve as a tool for investigating foraging preferences of highly mobile or migratory pinniped species.KEY WORDS: Leopard seal · Stable isotope · Vibrissae · von Bertalanffy · Antarctic · Prey switching Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 305: [249][250][251][252][253][254][255][256][257][258][259] 2005 al. 2004). Changes along the length of whale baleen have provided an isotopic record of seasonal variation in the location of feeding (Best & Schell 1996, Hobson & Schell 1998, Lee et al. 2005) and diet (Schell et al. 1989, Hobson & Schell 1998. Vibrissae may be a useful tissue for isotopic analysis and the study of longterm and seasonal dietary changes. Vibrissae lengths may be transformed into measurements of time, which can then be related to isotopic ratios.Growth rates have been determined for a number of pinniped species using dated vibrissae. Harbour seal vibrissae growth rates were irregular (Hirons et al. 2001) or variable (Zhao & Schell 2004), while growth rates in the case of grey seals Halichoerus grypus varied according to the length and age of the vibrissae and involved asynchronous shedding and discontinuous replacement (Greaves et al. 2004). Conversely, Steller sea lions Eumetobias jubatus displayed more consistent growth and annual retention of their vibrissae (Hirons et al. 2001). Greaves et al. (2004) suggested that vibrissae growth follows a von Bertalanffy growth curve.This study aims to transform vibrissae lengths into time lines using both a simple linear and von Bertalanffy growth model. With information gained through stable carbon and nitrogen isotope analysis of sequentially segmented vibrissae, their potential as indicators of seasonal cha...

The vocal repertoire, structure, and behavioral context of airborne vocalizations produced by Australian fur seals (Arctocephalus pusillus doriferus) are described using recordings made at a breeding colony on Kanowna Island, Bass Strait, Australia. The study identified six different call types: three produced by males (bark, guttural threat, and submissive call); five produced by females (bark, guttural threat, submissive call, growl, and pup attraction call) and the female attraction call produced by pups and yearlings. Vocalizations were compared according to age and sex classes. The overall structure and function of the pup attraction and female attraction call produced by females, yearlings, and pups, was similar. However, while similar in their overall appearance, certain call types have a lower fundamental frequency when compared with other fur seals. In addition, the male bark call alters in rate of production according to the context used, where calls are slower when males are stationary and advertising their territorial status and faster when males are involved in confrontations with other males or actively herding females. Further research is required to investigate changes in environmental conditions and 913 914 MARINE MAMMAL SCIENCE, VOL. 24, NO. 4, 2008 their effects on shaping the call structure and communication in Australian fur seals.Australian fur seals, A. pusillus doriferus, are the largest of all fur seal species (Warneke and Shaughnessy 1985), breeding on 10 islands located in Bass Strait, southeastern Australia (Kirkwood et al. 2005). The species follows the typical otariid breeding strategy, aggregating in dense social groups during a synchronous annual breeding season. Australian fur seals, like other fur seals are highly vociferous, using calls for territorial maintenance and defense, reproductive purposes, and the identification of individuals (Stirling and Warneke 1971). Vocalizations, in general, not only play an important role in reproduction and individual identity (Falls 1982, Roux andJouventin 1987) but can also indicate a range of other attributes of the caller including its location, species, kin, and sex (Janik 2005).In Australian fur seals, the male bark is the most prevalent call on rookeries and is used in different behavioral contexts and is suspected to show gradation in call structure. While Australian fur seals are taxonomically classed within the genus Arctocephalus, they display numerous vocal and behavioral traits resembling those of sea lions (Otariinae) (Warneke and Shaughnessy 1985). Stirling and Warneke (1971) provided qualitative descriptions of vocalizations produced by Australian fur seals. Currently, detailed quantitative information on the acoustic properties of Australian fur seal calls is lacking. This information is important as it allows for a method of comparison between species.Fur seals and sea lions are highly polygynous, displaying sexual dimorphism where males are up to four times larger than females (Riedman 1990). Males compete aggressively t...

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The detailed anatomical data provided are applicable to future functional and comparative anatomical studies, as well as providing a preliminary atlas for clinical investigation of conditions such as cryptococcal rhinosinusitis, a condition more common in the koala than in many other species.

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