, Volume 35, Issue 5, pp 865–875 | Cite as

Dry Years Decrease Abundance of American Alligators in the Florida Everglades

  • J. Hardin WaddleEmail author
  • Laura A. Brandt
  • Brian M. Jeffery
  • Frank J. Mazzotti
Original Research


The Everglades has been greatly reduced and is threatened by land use change and altered hydrology. The Comprehensive Everglades Restoration Plan calls for monitoring and assessment of key ecosystem attributes, one of which is abundance of American alligators. We examined 10 years of alligator night spotlight counts from Arthur R. Marshall Loxahatchee National Wildlife Refuge along two canals and in the interior marsh to determine trends and how dry years affect alligator abundance. Alligators showed population response to hydrologic conditions. In particular, there were declines in abundance after dry years followed by an apparent recovery in abundance in subsequent years. Increases in abundance were lower in the marsh than L-40 Canal. In addition, there was evidence that intensity of dry events affected population dynamics with greater declines observed in years with drier conditions. Results revealed that overall population of alligators increased from 2004 to 2013, but that increases varied by survey route. These results demonstrate that dry years cause a decline in alligator abundance proportional to the intensity of the dry event, and that it is important to make a distinction between canals and marsh when measuring alligator response to hydrology.


Arthur R. Marshall Loxahatchee National Wildlife Refuge Canal Comprehensive Everglades Restoration Plan Marsh Hierarchical model Hydrology 



We thank all of the volunteers who helped with the alligator surveys, D. Bucklin for data preparation, R. Chandler for assistance with the data analysis, B. Glorioso for assistance with figures, and the U.S. Geological Survey for maintaining the water level gauges. This study was funded by the U.S. Army Corps of Engineers Comprehensive Everglades Restoration Plan Restoration Coordination and Verification Monitoring and Assessment Program and the U.S. Geological Survey Greater Everglades Priority Ecosystems Sciences program. Views expressed here do not necessarily represent the views of the U.S. Fish and Wildlife Service. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.


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Copyright information

© US Government 2015

Authors and Affiliations

  • J. Hardin Waddle
    • 1
    Email author
  • Laura A. Brandt
    • 2
  • Brian M. Jeffery
    • 3
  • Frank J. Mazzotti
    • 3
  1. 1.National Wetlands Research CenterU.S. Geological SurveyLafayetteUSA
  2. 2.U.S. Fish and Wildlife ServiceDavieUSA
  3. 3.Fort Lauderdale Research and Education CenterUniversity of FloridaDavieUSA

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