Measurements of foraging success in a highly pelagic marine predator, the northern elephant seal
Article first published online: 28 JUL 2010
© 2010 The Authors. Journal compilation © 2010 British Ecological Society
Journal of Animal Ecology
Volume 79, Issue 6, pages 1146–1156, November 2010
How to Cite
Robinson, P. W., Simmons, S. E., Crocker, D. E. and Costa, D. P. (2010), Measurements of foraging success in a highly pelagic marine predator, the northern elephant seal. Journal of Animal Ecology, 79: 1146–1156. doi: 10.1111/j.1365-2656.2010.01735.x
- Issue published online: 28 JUL 2010
- Article first published online: 28 JUL 2010
- Received 12 April 2010; accepted 28 June 2010 Handling Editor: Graeme Hays
- drift rate;
- marine mammal;
- marine predator;
- transit rate
1. Identification of foraging behaviour and the ability to assess foraging success is critical to understanding individual and between-species variation in habitat use and foraging ecology. For pelagic predators, behaviour-dependent foraging metrics are commonly used to identify important foraging areas, yet few of these metrics have been validated.
2. Using the northern elephant seal as a model species, we validated the use of a behaviour-independent measure of foraging success (changes in drift rate) at the scale of the entire foraging migration, and then used this to assess a variety of common foraging metrics that are based on movement patterns and dive behaviour. Transit rate consistently provided the best estimate of daily foraging success, although the addition of other metrics provides insight into different foraging behaviours or strategies.
3. While positive changes in buoyancy occurred throughout most of the migrations, implying successful feeding across much of the north Pacific, the areas of most rapid changes in buoyancy occurred along a latitudinal band (40–50° N) corresponding to a dynamic hydrographic region including Subarctic Gyre and Transition Zone waters.
4. These results support the use of transit rate as an index of foraging success: a metric that is easily derived from tracking measurements on a wide range of marine species.