Social and reproductive behavior of crabeater seals ( Lobodon carcinophagus ) during the austral spring

Predictive species-environment models have numerous ecological and management applications, and can provide insight into the functional relationships between a species and its environment. Generalised linear models were used to develop predictive models of crabeater seal Lobodon carcinophaga distribution during the breeding season in relation to physical-oceanographic and ice-cover variables. Models were constructed from data collected on shipboard surveys in the packice off east Antarctica between 50 and 115°E from 1985 to 1987, and were tested from surveys in the same region from 1995 to 1997. Models of presence selected ocean depth as the only significant physical-oceanographic predictor variable for both breeding and non-breeding seals. Seals were most likely to be present on the ice at moderate ocean depths of approximately 2500 m. Unlike non-breeding seals, breeding seals were all but absent on the ice associated with depths of > 4000 m. The predicted distribution of presence comprised a band delineated by the shelf-break to the south and extending northwards for 1.5 to 5°latitude, with non-breeding seals having a more northerly limit than breeding seals. This band is coincident with the known distribution of the crabeater seals' primary food source (Antarctic krill), and also coincides with frontal features such as the Antarctic slope front and the southern boundary of the Antarctic Circumpolar Current, which are considered to be areas of enhanced primary and secondary productivity. The presence-depth models were improved by the inclusion of ice-cover variables. Breeding seals may avoid areas with a high proportion of all ice as floes < 20 m in size, because the chance of successfully weaning a pup in such areas is low.

Section: Discussionmentioning

confidence: 90%

Predicting the distribution of crabeater seals Lobodon carcinophaga off east Antarctica during the breeding season

Southwell¹,

Kerry²,

Ensor³

2005

“…Siniff et al 1979, Shaughnessy & Kerry 1989. It is not known if female crabeater seals also produce underwater vocalizations and if the occurrence of the high moan could possibly be attributed to females advertising their sexual receptivity.…”

Section: Mating Systemmentioning

confidence: 99%

“…Moreover, for pupping, crabeater seal females select ice floes based on floe size and physical characteristics (i.e. surface relief; Siniff et al 1979) which offer protection from predation by leopard seals and orcas. Changes affecting the availability and duration of availability of such sea-ice types might also directly affect crabeater seal populations, e.g.…”

Section: Implications Of a Changing Environment For Antarctic Pinnipedsmentioning

confidence: 99%

Acoustic ecology of Antarctic pinnipeds

Opzeeland¹,

Parijs²,

Bornemann³

et al. 2010

In aquatic-mating pinnipeds, acoustic communication plays an important role in male competition and mate attraction. Vocal repertoire size and composition during the breeding season varies between species and is presumed to be a product of interspecific differences in sexual selection. In this study, we examine seasonal and diel patterns in acoustic repertoire size, composition and call activity of 4 Antarctic pinniped species: Weddell seal Leptonychotes weddellii, leopard seal Hydrurga leptonyx, Ross seal Ommatophoca rossii and crabeater seal Lobodon carcinophaga. An

“…Scat and stomach contents analysis suggests that Adelie penguins Pygoscelis adeliae are eaten throughout the year, but are also the main prey item in the Prydz Bay region during the austral summer (Rogers & Bryden 1995, Hall-Aspland & Rogers 2004. Crabeater seals Lobodon carcinophagus become important in the diet between November and February when newly weaned pups are available as easy prey targets (Siniff & Bengtson 1977, Siniff et al 1979, Bengtson 1982, Siniff & Stone 1985. Krill and fish are preyed on throughout the summer from September to March whereas Antarctic silverfish Pleuragramma antarcticum predominated during winter (Green & Williams 1986).…”

Section: Introductionmentioning

confidence: 99%

Stable carbon and nitrogen isotope analysis reveals seasonal variation in the diet of leopard seals

Hall-Aspland¹,

Rogers²,

Canfield³

2005

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...