COS 59-2 - Variation in movement tactics and trophic interactions among American alligators creates unexpected habitat linkages

Wednesday, August 10, 2011: 8:20 AM
9C, Austin Convention Center
Adam E. Rosenblatt, Biological Sciences Department, Florida International University, North Miami, FL and Mike R. Heithaus, Marine Biology, Florida International University, North Miami, FL

Highly mobile top predators are hypothesized to spatially and/or temporally link disparate habitats through the combination of their movement and feeding patterns. Most studies have treated predators as homogenous groups that display similar behaviors, but recent studies suggest that individual specialization in habitat use and feeding could keep habitats compartmentalized. We used passive acoustic telemetry and stable isotope analysis from October 2007-December 2009 to investigate whether specialization in movement and feeding patterns of American alligators (Alligator mississippiensis) in an oligotrophic subtropical estuary created unexpected habitat linkages. 


Individual alligators adopted one of three relatively distinct movement tactics that were linked to variation in diets. Fifty-six percent of alligators regularly traveled from the upstream (freshwater/mid-estuary) areas into the downstream (marine) areas where salinities exceed those typically tolerated by alligators. Thirty-one percent of the alligators made regular trips from the mid-estuarine habitat into the upstream habitat; thirteen percent remained in the mid-estuary zone year-round. Stable isotopic analysis indicated that, unlike individuals remaining in the mid-estuary and upstream zones, alligators that used the downstream zone fed at least partially from marine food webs, and likely moved to access higher prey abundance at the expense of salt stress. Therefore, “commuting” alligators may link marine and estuarine/freshwater food webs in the coastal Everglades and create an upstream vector for allochthonous nutrient inputs into the estuary. This study lends further support to the hypothesis that large-bodied highly mobile predators faced with trade-offs are likely to exhibit individual specialization leading to habitat linkages, rather than compartmentalization.  However, the conditions under which this scenario occurs require further investigation.

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