title: Individual foraging strategies reveal niche overlap between endangered galapagos pinnipeds.
abstract: Most competition studies between species are conducted from a population-level approach. Few studies have examined inter-specific competition in conjunction with intra-specific competition, with an individual-based approach. To our knowledge, none has been conducted on marine top predators. Sympatric Galapagos fur seals (Arctocephalus galapagoensis) and sea lions (Zalophus wollebaeki) share similar geographic habitats and potentially compete. We studied their foraging niche overlap at Cabo Douglas, Fernandina Island from simultaneously collected dive and movement data to examine spatial and temporal inter- and intra-specific competition. Sea lions exhibited 3 foraging strategies (shallow, intermediate and deep) indicating intra-specific competition. Fur seals exhibited one foraging strategy, diving predominantly at night, between 0-80 m depth and mostly at 19-22 h. Most sea lion dives also occurred at night (63%), between 0-40 m, within fur seals' diving depth range. 34% of sea lions night dives occurred at 19-22 h, when fur seals dived the most, but most of them occurred at dawn and dusk, when fur seals exhibited the least amount of dives. Fur seals and sea lions foraging behavior overlapped at 19 and 21 h between 0-30 m depths. Sea lions from the deep diving strategy exhibited the greatest foraging overlap with fur seals, in time (19 h), depth during overlapping time (21-24 m), and foraging range (37.7%). Fur seals foraging range was larger. Cabo Douglas northwest coastal area, region of highest diving density, is a foraging "hot spot" for both species. Fur seals and sea lions foraging niche overlap occurred, but segregation also occurred; fur seals primarily dived at night, while sea lions exhibited night and day diving. Both species exploited depths and areas exclusive to their species. Niche breadth generally increases with environmental uncertainty and decreased productivity. Potential competition between these species could be greater during warmer periods when prey availability is reduced.
authors: Department of Behavioral Biology, Bielefeld University, Bielefeld, North Rhine-Westphalia, Germany. stella.villegas@gmail.com
authors: Stella
authors: S
authors: Villegas-Amtmann
authors: Jana W E
authors: JW
authors: Jeglinski
authors: Daniel P
authors: DP
authors: Costa
authors: Patrick W
authors: PW
authors: Robinson
authors: Fritz
authors: F
authors: Trillmich
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D010872:Caniformia; D016000:Cluster Analysis; D017753:Ecosystem; D056727:Endangered Species; D005247:Feeding Behavior; D005260:Female; D062206:Spatial Analysis
references: Proc Biol Sci. 1999 Jun 7;266(1424):1127-32
references: 10406130
references: BMC Evol Biol. 2008 May 16;8:150
references: 18485220
references: PLoS One. 2010 Jan 15;5(1):e8677
references: 20090942
references: J Exp Biol. 2007 Jan;210(Pt 2):278-89
references: 17210964
references: Biol Bull. 1950 Oct;99(2):237-58
references: 14791422
references: Proc Natl Acad Sci U S A. 2009 Aug 4;106(31):12788-93
references: 19620720
references: J Anim Ecol. 2013 May;82(3):694-706
references: 23351022
references: Science. 2003 Jan 10;299(5604):217-21
references: 12522241
references: Am Nat. 2003 Jan;161(1):1-28
references: 12650459