Pitching a new angle on elephant seal dive patterns

SALA J.E.; QUINTANA F,; WILSON, R.; DIGNIANI J.; LEWIS M.; CAMPAGNA C,

POLAR BIOLOGY

SPRINGER

Lugar: KIEL; Año: 2011 vol. DOI p. 1 - 6

0722-4060

Extended breath-hold capabilities of marine endotherms are enhanced by physiological adaptations, larger body size and strategies for reducing energy expenditure such as minimizing costs of transport by drifting. We used enhanced multiple channel loggers recording depth and body orientation (pitch and roll) on 5 juvenile southern elephant seals (Mirounga leonina) to expand what is known about their diving behaviour. We used standard descriptions of elephant seal dive profile type provided by the literature gained from use of simple time-depth recorders (currently grouped into types A to E) and reinterpreted their form and function using the additional orientation data. We argue that the dives can be conveniently described by function during descent, bottom or ascent characteristics, with each being considered as a separate entity. Thus, currently accepted dive profile types are actually composed of three major types of descent: rapid, where vertical travel is enhanced (such as occurs in type-A, -D, -E dives); slow, where rate of change of depth is minimized (as in type-C dives); and parabolic, where horizontal displacement in maximized (as in type B dives). Following descent, all rapid descent dives may have bottom phases that indicate rest, travel, prey searching, or prey pursuit or a combination of these, and we propose that it is animal state and environmental circumstance that determines whether these dives ultimately may be classified as type A, D or E. Ascent phases for all dives were similar and reflect a common process of moving the animal from the depths to the surface with minimal effort within an appropriate time.