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Size, sex and individual‐level behaviour drive intrapopulation variation in cross‐ecosystem foraging of a top‐predator
Author(s) -
Nifong James C.,
Layman Craig A.,
Silliman Brian R.
Publication year - 2015
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1111/1365-2656.12306
Subject(s) - foraging , apex predator , predation , alligator , ecosystem , ecology , marine ecosystem , biology , predator , habitat , estuary , keystone species
SummaryLarge‐bodied, top‐predators are often highly mobile, with the potential to provide important linkages between spatially distinct food webs. What biological factors contribute to variation in cross‐ecosystem movements, however, have rarely been examined. Here, we investigated how ontogeny (body size), sex and individual‐level behaviour impacts intrapopulation variation in cross‐ecosystem foraging (i.e. between freshwater and marine systems), by the top‐predator Alligator mississippiensis . Field surveys revealed A. mississippiensis uses marine ecosystems regularly and are abundant in estuarine tidal creeks (from 0·3 to 6·3 individuals per km of creek, n = 45 surveys). Alligator mississippiensis captured in marine/estuarine habitats were significantly larger than individuals captured in freshwater and intermediate habitats. Stomach content analysis (SCA) showed that small juveniles consumed marine/estuarine prey less frequently (6·7% of individuals) than did large juveniles (57·8%), subadult (73%), and adult (78%) size classes. Isotopic mixing model analysis ( SIAR ) also suggests substantial variation in use of marine/estuarine prey resources with differences among and within size classes between sexes and individuals (range of median estimates for marine/estuarine diet contribution = 0·05–0·76). These results demonstrate the importance of intrapopulation characteristics (body size, sex and individual specialization) as key determinants of the strength of predator‐driven ecosystem connectivity resulting from cross‐ecosystem foraging behaviours. Understanding the factors, which contribute to variation in cross‐ecosystem foraging behaviours, will improve our predictive understanding of the effects of top‐predators on community structure and ecosystem function.