We are pleased to announce the publication of our paper:

Jeglinski, JWEJ, Werner, C, Götz, K, Costa, DP & 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, doi: 10.1111/1365-2656.12019


Summary
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.

Key-words: Arctocephalus galapagoensis, biologging, foraging competition, habitat segregation,
ontogeny, stable isotopes, Zalophus wollebaeki

http://onlinelibrary.wiley.com/doi/10.1111/1365-2656.12019/abstract


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