Project Summary Sheet

Project: American alligator distribution, thermoregulation, and biotic potential relative to hydroperiod in the Everglades

Web Site: www.fcsc.usgs.gov (see http://cars.er.usgs.gov/)

Location: Central/southern Everglades

Principal Investigator: Dr. Kenneth G. Rice, USGS - Biological Resources Division, ken_g_rice@usgs.gov, H. Franklin Percival, USGS - Florida Cooperative Fish and Wildlife Research Unit, Timothy S. Gross, USGS - Biological Resources Division

Project Personnel:

Other Supporting Organizations: USGS/BRD, NPS

Associated Projects: Complement of ATLSS Program

Overview & Status: Over the last one hundred years the hydrology of the Everglades has been greatly altered by mankind. Efforts to repair the functioning of the ecosystem are using a multicomponent model, the Across Trophic Level System Simulation (ATLSS), to predict the response of native flora and fauna to alterative water delivery scenarios. This study was designed to provide information on the natural history and population functioning of the American alligator in the Everglades for construction of an ATLSS American alligator population model and to investigate restoration needs and status of the alligator in the Everglades ecosystem. We initiated a five year study on the home range, daily movement, habitat use, thermoregulation, and body temperature patterns of alligators in both Shark Slough, Everglades National Park, and in Water Conservation area 3A North. A total of 66 alligators were captured and surgically implanted with radio-transmitters. A subset of 29 of these also were implanted with temperature recording data loggers. Data loggers recorded core body temperature simultaneously at 72 minute intervals for 1 year. Weekly aerial telemetry locations were collected beginning 1 January 1997 to estimate home range size. Weeklong intensive sampling efforts conducted from 7 November 1997 to 31 July 1998 were used to estimate daily movement and habitat use.

Needs & Products: This study encompasses 2 of the critical projects for restoration of crocodilian populations determined by a meeting of over 40 biologists, managers, and administrators held in Homestead in December, 1998. Alligators are a key indicator component and are used as ecological attributes and measures in the Everglades Ridge & Slough and Marl Prairie/Rocky Glades Conceptual Ecosystem Models. For these models, this study directly addresses the critical ecological pathways, examines the effects of compartmentalization on wildlife populations and addresses hypotheses concerning the proposed linkage between water management practices and reduced production and survival of alligators. This study addresses critical information needs such as identified in South Florida Ecosystem Restoration: Scientific Information Needs by the Science Subgroup of the South Florida Ecosystem Restoration Task Force including recovery of populations of selected indicator species, enhancing the prescription of minimum area, and identification of ecological assessment indicators. We also investigate the decline in numbers and shift in distribution of the American alligator. Specific proposed performance measures relate to the alligator such as reduce frequency of water dry-outs during courtship period and duration of below ground water depths to increase alligator nesting and re-establish hydrological predictability for relationship between peak early wet season water levels and late wet season levels to reduce alligator nest flooding.

Application to Everglades Restoration: We investigate the decline in numbers and shift in distribution of the American alligator identified as an Everglades National Park Major Issue and information need in South Florida Ecosystem Restoration: Scientific Information Needs by the Science Subgroup of the South Florida Ecosystem Restoration Task Force. Specific proposed performance measures relate to the alligator such as reduce frequency of water dry-outs during courtship period and duration of below ground water depths to increase alligator nesting and re-establish hydrological predictability for relationship between peak early wet season water levels and late wet season levels to reduce alligator nest flooding.