American crocodiles (Crocodylus acutus) as restoration bioindicators in the Florida Everglades

PLoS One. 2021 May 19;16(5):e0250510. doi: 10.1371/journal.pone.0250510. eCollection 2021.

Abstract

The federally threatened American crocodile (Crocodylus acutus) is a flagship species and ecological indicator of hydrologic restoration in the Florida Everglades. We conducted a long-term capture-recapture study on the South Florida population of American crocodiles from 1978 to 2015 to evaluate the effects of restoration efforts to more historic hydrologic conditions. The study produced 10,040 crocodile capture events of 9,865 individuals and more than 90% of captures were of hatchlings. Body condition and growth rates of crocodiles were highly age-structured with younger crocodiles presenting with the poorest body condition and highest growth rates. Mean crocodile body condition in this study was 2.14±0.35 SD across the South Florida population. Crocodiles exposed to hypersaline conditions (> 40 psu) during the dry season maintained lower body condition scores and reduced growth rate by 13% after one year, by 24% after five years, and by 29% after ten years. Estimated hatchling survival for the South Florida population was 25% increasing with ontogeny and reaching near 90% survival at year six. Hatchling survival was 34% in NE Florida Bay relative to a 69% hatchling survival at Crocodile Lake National Wildlife Refuge and 53% in Flamingo area of Everglades National Park. Hypersaline conditions negatively affected survival, growth and body condition and was most pronounced in NE Florida Bay, where the hydrologic conditions have been most disturbed. The American crocodile, a long-lived animal, with relatively slow growth rate provides an excellent model system to measure the effects of altered hydropatterns in the Everglades landscape. These results illustrate the need for continued long-term monitoring to assess system-wide restoration outcomes and inform resource managers.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alligators and Crocodiles / growth & development
  • Alligators and Crocodiles / physiology*
  • Animals
  • Biomass*
  • Body Size
  • Conservation of Natural Resources*
  • Fertility
  • Florida
  • Wetlands*

Associated data

  • Dryad/10.5061/dryad.nzs7h44q7

Grants and funding

Funding for this work was supported by grants to FJM by U.S. Army Corps of Engineers (USACE https://www.usace.army.mil/) Cooperative Agreement Research Work Order #268, U.S. National Park Service (https://www.nps.gov/) CESU Cooperative Agreement #H5000060106, U.S. Geological Survey (USGS https://www.usgs.gov/) Greater Everglades Priority Ecosystems Science (PES) Program Cooperative Agreement #G15AC00278, Florida Power and Light Company (https://www.fpl.com/) Contract #02377545, Lacoste/Save Your Logo Fonds de Dotation pour la Biodiversité (http://www.saveyourlogo.org/en/) #F017137, U.S. Fish and Wildlife Service (USFWS https://www.fws.gov/) Cooperative Agreement #1448-40181-99-G, U.S. Navy (https://www.navy.mil/) Agreement #W9126G-16-2-0002. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.