Factors affecting individual foraging specialization and temporal diet stability across the range of a large “generalist” apex predator
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Individual niche specialization (INS) is increasingly recognized as an important component of ecological and evolutionary dynamics. However, most studies that have investigated INS have focused on the effects of niche width and inter- and intraspecific competition on INS in small-bodied species for short time periods, with less attention paid to INS in large-bodied reptilian predators and the effects of available prey types on INS. We investigated the prevalence, causes, and consequences of INS in foraging behaviors across different populations of American alligators (Alligator mississippiensis), the dominant aquatic apex predator across the southeast US, using stomach contents and stable isotopes. Gut contents revealed that, over the short term, although alligator populations occupied wide ranges of the INS spectrum, general patterns were apparent. Alligator populations inhabiting lakes exhibited lower INS than coastal populations, likely driven by variation in habitat type and available prey types. Stable isotopes revealed that over longer time spans alligators exhibited remarkably consistent use of variable mixtures of carbon pools (e.g., marine and freshwater food webs). We conclude that INS in large-bodied reptilian predator populations is likely affected by variation in available prey types and habitat heterogeneity, and that INS should be incorporated into management strategies to efficiently meet intended goals. Also, ecological models, which typically do not consider behavioral variability, should include INS to increase model realism and applicability.
KeywordsAmerican alligator Alligator mississippiensis Stomach content analysis Stable isotope analysis Food web
We thank Michael Delany, Steven Gabrey, and Amanda Rice for generously allowing us to use their alligator stomach contents data. This research was made possible by funding from the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Grant No. DBI-0620409 and from the National Oceanic and Atmospheric Administration under Award No. NA10NOS4200022 (09102903). Additional funding was provided by Florida International University (FIU) and the University of Florida (UF). A.E.R. was supported by an FIU Dissertation Year Fellowship during manuscript preparation. All animal care and use was performed in accordance with the UF Institutional Animal Care and Use Committee (IACUC) under Protocol No. 201005071, the FIU IACUC under Protocol No. 09-015 and 09-013, and the Kennedy Space Center IACUC under Protocol No. GRD-06-044. All field collections were performed under FFWCC Scientific Collecting Permit No. SPGS-10-44R and SPGS-10-43, Georgia Department of Natural Resources Scientific Collecting Permit No. 29-WBH-10-33, and Everglades National Park Permit No. 0024, 0025, and 0031. We thank all the volunteers who assisted with field work and data collection, especially Phil Matich, Kirk Gastrich, Katy Cameron, Greg Mineau, and Derek Burkholder. Use of trade, product, or firm names does not imply endorsement by the U.S. Government or the authors. All work carried out in this study comply with the current laws of the USA.
Conflict of interest
We declare that we have no conflict of interest.
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