Fine-scale three-dimensional spatial use by diving, lactating female Weddell seals Leptonychotes weddellii

Abstract

Despite the importance of fine-scale spatial use in understanding an animal's foraging ecology, these data cannot readily be collected for free-ranging marine mammals. We used an acoustic positioning system to quantify, for the first time, the fine-scale 3-dimensional (3D) spatial use of free-ranging Weddell seals swimming under ice. Unlike many other phocid species, lactating Weddell seals spent up to 25% of their time diving. Given the limited foraging range imposed on the seals by the fast ice upon which they breed, this could lead to prey depletion and even inter-specific competition. The seals focused their underwater activity on a relatively small region associated with a steep bottom contour, using the entire water column, with very little time spent at the bottom. This behaviour is consistent with feeding on bentho-pelagic prey such as Pleurogramma antarcticum. The 3D profile of individual dives consisted of the seals making simple, directed dives which gradually converged with the ocean floor. There was some variation from this pattern, usually associated with increased searching time. Such focused foraging activity may result in local prey depletion and intraspecific competition.KEY WORDS: Three-dimensional tracking · Acoustic tracking · Habitat use · Intra-specific competition · Weddell seals Resale or republication not permitted without written consent of the publisher

Capital Expenditure and Income (Foraging) during Pinniped Lactation: The Example of the Weddell Seal (Leptonychotes weddellii)

“…The diving behavior of Weddell seals, including lactating females as well as nursing, weaned, and yearling animals, has been extensively investigated with time-depth recorders, or TDRs, including satellite-uplinked instruments (e.g., Kooyman, 1967;Testa et al, 1989;Burns et al, , 1999Castellini et al, 1992;Sato et al, 2002Sato et al, , 2003Williams et al, 2004;Fuiman et al, 2007). The recent development of instrumentation that records directional information ( Harcourt et al, 2000;Davis et al, 2001;Hindell et al, 2002;Mitani et al, 2003) allows examination of dive behavior in three-dimensional space. Although food intake requires diving, even deep diving need not entail food consumption.…”

All at sea with animal tracks; methodological and analytical solutions for the resolution of movement

“…/j.dsr2.2006 VHF telemetry (Hooker et al, 2002 and references therein), satellite tracking telemetry (Ferraroli et al, 2004;Hays et al, 2004a;Jouventin and Weimerskirch, 1990;Sims et al, 2005), GPS technology (Weimerskirch et al, 2005), and geolocation or global location sensing (e.g., Block et al, 2001;Hill, 1994;Wilson et al, 1994). Only two methods work underwater, these being acoustic telemetry (e.g., Hindell et al, 2002) and dead-reckoning (Wilson and Wilson, 1988). Acoustic telemetry necessitates that receivers be within a few hundred metres of the animal to be tracked so that fast and widely ranging species are difficult to access with this method.…”

Identification of foraging dives in free-ranging Weddell seals Leptonychotes weddellii: confirmation using video records

“…The diving habits of the Weddell seal Leptonychotes weddellii have been well studied using time-depth recorders and satellite-linked, time-depth recorders (Kooyman 1981, Castellini et al 1992, Testa 1994, acoustic tracking (Harcourt et al 2000, Hindell et al 2002, dead reckoners (Davis et al 1999(Davis et al , 2003, and geomagnetic and acceleration recorders (Mitani et al , 2004. These seals are highly adapted for hunting in the cold, dark, ice-covered waters of Antarctica (Kooyman 1981, Castellini et al 1992.…”

“…Marshall 1998, Davis et al 1999, Fuiman et al 2002, Hooker et al 2002, Sato et al 2002, Watanabe et al 2003. These methods have already shown that some of the previous inferences about foraging behavior were incorrect (Lesage et al 1999, Davis et al 2003.The diving habits of the Weddell seal Leptonychotes weddellii have been well studied using time-depth recorders and satellite-linked, time-depth recorders (Kooyman 1981, Castellini et al 1992, Testa 1994, acoustic tracking (Harcourt et al 2000, Hindell et al 2002, dead reckoners (Davis et al 1999(Davis et al , 2003, and geomagnetic and acceleration recorders (Mitani et al , 2004. These seals are highly adapted for hunting in the cold, dark, ice-covered waters of Antarctica (Kooyman 1981, Castellini et al 1992.…”