Silence as an Antipredation Strategy by Weddell Seals

• Main Authors: Thomas, Jeanette A., Ferm, Lisa M., Kuechle, Valerian B.
• Other Authors: NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA
• Format: Text
• Language: English
• Published: 1989
• Subjects: Biological Oceanography; Acoustics; *SEALS(MAMMALS); *UNDERWATER SOUND SIGNALS; *MARINE BIOLOGICAL NOISE; EDGES; ISOLATION; RATES; ACOUSTIC DETECTION; SEASONAL VARIATIONS; ICE; HABITATS; COLONIES(BIOLOGY); QUIET; ANTARCTIC REGIONS; WHALES; STABILIZED PLATFORMS; BREEDING; RISK; ICE BREAKUP; REPRINTS; POSITION(LOCATION); WEDDELL SEALS; SILENCE; Antarctic; Austral; McMurdo Sound; McMurdo Station; Weddell; Antarc*; Antarctica; Leopard Seals; Weddell Seal; Weddell Seals
• Online Access: http://www.dtic.mil/docs/citations/ADA208289; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA208289

In McMurdo Sound, Antarctica, Weddell seals return to traditional breeding colonies on shorefast ice each austral spring. This fast ice provides a stable platform, over a 2-month period, for raising pups and a fixed location for establishing underwater mating territories. However, it also may provide protection from predators. Weddell seals are the only marine mammal in the shorefast ice of McMurdo Sound from Oct through early Dec. When killer whales and leopard seals arrive in mid-December, they work the ice edge for available prey. As the fast ice breaks up, leads provide access to nearby Weddell seal colonies. In late December, icebreakers open a lead for entry to McMurdo Station. Killer whales and leopard seals use this large lead and its tributaries to move closer to Weddell seal colonies. The objective of this study was to document the rate of underwater calls from Weddell seals throughout the breeding season and to monitor changs in this rate associated with the arrival of leopard seals and killer whales. Weddell seals have 34 underwater sounds. We hypothesize that if fast ice provides Weddell seals a refuge from predators during breeding, then Weddell seals can risk advertising and defending underwater mating territories with loud sounds. However, when the fast ice habitat no longer provides isolation from predators, Weddell seals become silent to prevent detection. Marine biological noise, Seals/mammals. Reprints. Sponsored in part by NSF grants DPP 77-2194 and DPP 77-21646.