Same size – same niche? Foraging niche separation between sympatric juvenile Galapagos sea lions and adult Galapagos fur seals
Article first published online: 25 JAN 2013
© 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society
Journal of Animal Ecology
Volume 82, Issue 3, pages 694–706, May 2013
How to Cite
Jeglinski, J. W. E., Goetz, K. T., Werner, C., Costa, D. P., Trillmich, F. (2013), Same size – same niche? Foraging niche separation between sympatric juvenile Galapagos sea lions and adult Galapagos fur seals. Journal of Animal Ecology, 82: 694–706. doi: 10.1111/1365-2656.12019
- Issue published online: 15 APR 2013
- Article first published online: 25 JAN 2013
- Manuscript Accepted: 8 OCT 2012
- Manuscript Received: 26 MAR 2012
- German Science Foundation . Grant Number: TR 105/19-1
- E & P Sound and Marine Life Joint Industry Project of the International Association of Oil and Gas Producers. Grant Number: JIP2207-23
- Arctocephalus galapagoensis ;
- foraging competition;
- habitat segregation;
- stable isotopes;
- Zalophus wollebaeki
- In vertebrates, patterns of resource utilization change throughout development according to age- and or size-specific abilities and requirements. Thus, interspecific competition affects different age classes differently.
- Adults of sympatric species often show distinct foraging niche segregation, but juvenile resource use might overlap with adult competitors of similar body size. Resultant negative effects on juveniles can have important consequences for population dynamics, yet such interactions have received little attention in studies of mammalian communities.
- Using GPS tracking devices, time-depth recorders and stable isotope data, we compared diving depth, activity time, trophic position and foraging habitat characteristics to investigate foraging niche overlap between similar-sized sympatric juvenile Galapagos sea lions (Zalophus wollebaeki) and adult Galapagos fur seals (Arctocephalus galapagoensis) and compared each group with much larger-bodied adult Galapagos sea lions.
- We found little indication for direct competition but a complex pattern of foraging niche segregation: juvenile sea lions and adult fur seals dived to shallow depths at night, but foraged in different habitats with limited spatial overlap. Conversely, juvenile and adult sea lions employed different foraging patterns, but their foraging areas overlapped almost completely.
- Consistency of foraging habitat characteristics between juvenile and adult sea lions suggests that avoidance of competition may be important in shaping foraging habitat utilization. Resultant specialization on a limited habitat could contribute to low sea lion numbers that contrast with high fur seal abundance. Our data suggest that exploitation by multiple predators within spatially restricted foraging ranges of juveniles might negatively impact juvenile foraging success and ultimately influence population dynamics.