Cephalopod remains in scats of Weddell seals (Leptonychotes weddellii) at Cape Shirreff, South Shetland Islands, Antarctica

Abstract

The diet of Weddell seals (Leptonychotes weddellii) varies regionally, and fish and cephalopods are thought to be the most important food source. However, there is limited information on the cephalopod component of the Weddell seal's diet in the South Shetland Islands. We investigated cephalopod remains in the diet of Weddell seals by analysing 21 scats collected on three beaches at Cape Shirreff, Livingston Island, Antarctica, from 1 to 20 February 1999. Although the number of scats is small and collected from only 1 month a long time ago, fish and cephalopods were present in 21 and 16 of the scats, respectively. Only cephalopods of the order Octopoda were represented. Thaumeledone sp. was the most abundant prey species in terms of numbers, followed by Pareledone charcoti and P. turqueti. The latter two species showed the highest frequency of occurrence in scats (10 and 9, respectively). Graneledone macrotyla, Opistoteuthis sp., Argonauta sp., Haliphron sp. and Thaumeledone sp. are new species identified in the diet of Weddell seals in the present study, but all made a negligible contribution to their diet at Cape Shirreff. Our findings agree with previous dietary studies of Weddell seals at other localities in the South Shetland Islands and the Antarctic Peninsula, which showed a relatively greater contribution of octopods to the diet compared with squid in summer.

Observation of a Gelatinous Octopod, Haliphron atlanticus, along the Southern West Mariana Ridge: A Unique Cephalopod of Continental Slope and Mesopelagic Communities

“…Haliphron atlanticus has been detected in the diets of the Hawaiian monk seal, Monachus schauinslandi [81], and South Shetland Island Weddell seals, Leptonychotes weddellii [82], and it may be scavenged at the surface by seabirds after predation events by large predators. It has been detected in South Atlantic albatross [43,44], Azores Cory's shearwater, Calonectris diomedea [42], and Monterey Bay California Pacific northern fulmar, Fulmarus glacialis rogersii [83] diets.…”

Complementary use of stable isotopes and fatty acids for quantitative diet estimation of sympatric predators, the Antarctic pack-ice seals

“…Leopard seals feed on a variety of prey at different trophic levels, such as krill, fish, penguins and other seals (Siniff and Stone 1985;Green and Williams 1986;Rogers and Bryden 1995;Hall-Aspland and Rogers 2004;Casaux et al 2009;Botta et al 2018;Krause et al 2020); whereas crabeater seals specialise almost exclusively on krill (Laws 1977;Hückstädt et al 2012), and Weddell seals prey mostly on fish, but also on cephalopods (Burns et al 1998;Zhao et al 2004;Casaux et al 2011;Acevedo et al 2015;Goetz et al 2016). Thus, we evaluated how the combined use of FAs and SIs performs to estimate the relative dietary composition of predators with different foraging strategies.…”

“…Until a few decades ago, our understanding of their ecology consisted of limited observations as they came ashore or near the surface. Traditionally, we have relied on methods such as stomach and scat content analyses to study their foraging ecology (Hall-Aspland and Rogers 2004 ; Acevedo et al 2015 ). Although these techniques provide valuable information, they are usually based on few and recent feeding events, and have known biases related to identification of prey items and differential digestion rates (Gales and Cheal 1992 ), making it difficult to answer complex ecological questions.…”

Trophic ecology drives trace element concentrations in the Antarctic octopod community

“…Benthic octopods have a role as both predator and prey, and are crucial in the transfer of energy and trace elements in the Antarctic food web, linking low trophic level consumers to high-level predators (Allcock,1997;2005;Allcock et al, 2001;Daly, 1996;Piatkowski et al, 1998;Strugnell et al, 2017). A wide variety of predators feed on benthic octopods, for example: elephant seals (Mirounga leonine, Burdman et al, 2015;Daneri et al, 2000;Rodhouse et al, 1992), Weddell seals (Leptonychotes weddellii, Acevedo et al, 2015;Casaux et al, 1997;Lipinski and Woyciechowski, 1981;Negri et al, 2016), Patagonian toothfish (Dissostichus eleginoides, Xavier et al, 2002), and the black-browed albatross (Thalassarche melanophris, Xavier and Croxall, 2007). In turn, benthic octopods prey on crustaceans, polychaetes, bivalves, gastropods (Daly, 1996), and amphipods (Daneri et al, 2000;Piatkowski et al, 2003).…”