Abstract
New data are reported from analyses of stomach contents from 114 long-finned pilot whales mass-stranded at four locations around Tasmania, Australia from 1992–2006. Identifiable prey remains were recovered from 84 (74%) individuals, with 30 (26%) individuals (17 females and 13 males) having empty stomachs. Prey remains comprised 966 identifiable lower beaks and 1244 upper beaks, belonging to 17 families (26 species) of cephalopods. Ommastrephidae spp. were the most important cephalopod prey accounting for 16.9% by number and 45.6% by reconstructed mass. Lycoteuthis lorigera was the next most important, followed by Ancistrocheirus lesueurii. Multivariate statistics identified significant differences in diet among the four stranding locations. Long-finned pilot whales foraging off Southern Australia appear to be targeting a diverse assemblage of prey (≥10 species dominated by cephalopods). This is compared to other similar studies from New Zealand and some locations in the Northern Hemisphere, where the diet has been reported to be primarily restricted to ≤3 species dominated by cephalopods. This study emphasises the importance of cephalopods as primary prey for Southern long-finned pilot whales and other marine vertebrates, and has increased our understanding of long-finned pilot whale diet in Southern Ocean waters.
Highlights
Cephalopods comprise a major portion of the diets of many marine vertebrates, and are a key trophic link in the Southern Ocean ecosystem [1,2,3,4,5,6]
A total of 253 LFPWs mass-stranded at four locations around Tasmania from 1992–2008 (Bicheno, Maria Island, Marion Bay and Ocean Beach) (Fig 1)
S. australis/O. maorum, and H. atlantica/P. massyae were considered important prey for LFPWs recovered from Maria Island and Ocean Beach, respectively
Summary
Cephalopods comprise a major portion of the diets of many marine vertebrates (cetaceans, seals, birds and fish), and are a key trophic link in the Southern Ocean ecosystem [1,2,3,4,5,6] Marine mammals spend their lives at sea and afford little opportunity for direct observation of feeding. The most commonly stranded cetacean (by number of individuals) is the longfinned pilot whale, Globicephala melas (LFPW), where of 1568 individuals stranded (69% of all individuals during this time period), only 30 (8.9%) of the 336 stranding events were LFPWs. LFPWs strand in Tasmania throughout the year (except May and June), there is a distinct stranding peak during summer, from September to December (DPIPWE unpublished data). This apparent seasonality is observed in LFPWs that strand along the New Zealand coastline [2, 3, 19, 20], and be as a result of long-distance migrations of LFPWs past Tasmania during summer, or reflective of seasonal changes in prey distribution from offshore areas onto the continental shelf and near-shore waters
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