[MARMAM] New paper: Foraging niche segregation of Galapagos sea lions and fur seals

Jana Jeglinski jjeglinski at uni-bielefeld.de
Wed Jan 30 03:03:02 PST 2013

Dear all,

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

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
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 *

Please see below:


Best wishes,

Dr. Jana W.E Jeglinski

Galapagos Sea Lion Project
University of Bielefeld
Department of Animal Behaviour
Morgenbreede 45
33615 Bielefeld
+49 521 106 2192

Long Marine Lab
University of Santa Cruz
Santa Cruz CA
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