A method for reconstructing three-dimensional dive profiles of marine mammals using geomagnetic intensity data: results from two lactating Weddell seals
The under-ice behavior of two free-ranging female Weddell seals (Leptonychotes weddellii) was studied using geomagnetic, acceleration and velocity sensors at Big Razorback Island in McMurdo Sound, Antarctica. The seals' body angle and posture were calculated from the acceleration data and the heading from the geomagnetic intensity data. Together with swim speed, the seals' three-dimensional underwater dive path, heading and even posture were reconstructed for each dive. Each instrument was deployed for 2 days, during which time these females made multiple, deep (≥50 m) dives, with average maximum depths of 236±27 m (n=4) and 244±121 m (n=40). Each seal appeared to choose a particular heading on which to descend. These headings were significantly different between seals and bouts (Watson's U 2 test, P<0.05). These new instruments and methodologies are shown to provide valuable information on the fine-scale and complex movements of diving animals.
KeywordsSwimming Speed Dead Reckoning Weddell Seal Dive Duration Body Angle
We thank C. Counard, S. Dahle, D. MacNulty, K. Krysl, H. Reider, E. Morton, and G. Wong for their assistance with the fieldwork. We are also grateful to H. Tanaka, S. Minamikawa, and C. Tsushima for the propeller calibration experiments. The experimental protocol was previously approved by the National Marine Fisheries Service, Marine Mammal Protection Agency. The fieldwork was conducted at McMurdo Station of the United States Antarctic Program. This work was partly supported by a Grant-in-Aid from the Japan Society for the promotion of Science (11691197 and 14405027), the Sasakawa Scientific Research Grant from the Japan Science Society (14-368M), and the National Science Foundation (OPP-9420818).
- Green K, Burton HR (1987) Seasonal and geographical variation in the food of Weddell seals, Leptonychotes weddellii, in Antarctica. Aust Wildl Res 14:475–489Google Scholar
- Hindell MA, Harcourt R, Waas JR, Thompson D (2002) Fine-scale three-dimensional spatial use by diving, lactating female Weddell seals Leptonychotes weddellii. Mar Ecol Prog Ser 242:275–284Google Scholar
- Kooyman GL (1968) An analysis of some behavioral and physiological characteristics related to diving in the Weddell seal. Antarct Res Ser 11:227–261Google Scholar
- Le Boeuf BJ, Naito Y, Huntley AC, Asaga T (1989) Prolonged, continuous, deep diving by northern elephant seals. Can J Zool 67:2514–2519Google Scholar
- Naito Y, Le Boeuf BJ, Asaga T, Huntley AC (1989) Long-term diving records of an adult female northern elephant seal. Antarct Rec 33:1–9Google Scholar
- Sato K, Mitani Y, Cameron MF, Siniff DB, Watanabe Y, Naito Y (2002) Deep foraging dives in relation to the energy depletion of Weddell seal (Leptonychotes weddellii) mothers during lactation. Polar Biol 25:696–702Google Scholar
- Sato K, Mitani Y, Cameron MF, Siniff DB, Naito Y (2003) Factors affecting stroking patterns and body angle in diving Weddell seals under natural condition. J Exp Biol (in press)Google Scholar
- Simpkins MA, Kelly BP, Wartzok D (2001) Three-dimensional analysis of search behaviour by ringed seals. Anim Behav 62:67–72Google Scholar
- Stirling I (1966) A technique for handling live seals. J Mammal 47:543–544Google Scholar
- Wilson RP, Wilson MP (1988) Dead reckoning: a new technique for determining penguin movements at sea. Meeresforschung 32:155–158Google Scholar
- Wilson RP, Wilson MP, Link R, Mempel H, Adams NJ (1991) Determination of movements of African penguins Spheniscus demersus using a compass system: dead reckoning may be an alternative to telemetry. J Exp Biol 157:557–564Google Scholar
- Zar JH (1984) Circular distributions: hypothesis testing. Biological analysis, 2nd edn. Prentice-Hall, Englewood Cliffs, NJ, pp 440–469Google Scholar