role of american alligator (alligator mississippiensis) in measuring restoration success in the florida everglades
Role of American Alligator (Alligator mississippiensis) in Measuring Restoration Success in the Florida Everglades
Poster presented April 2003, at the Greater Everglades Ecosystem Restoration Conference
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Currently, restoration of hydrologic pattern and ecological function is beginning in the Everglades. Due to the alligators ecological importance and sensitivity to hydrology, salinity, habitat and system productivity, the species was chosen as an indicator of restoration success. A number of biological attributes (relative density, relative body condition, nesting effort, and nesting success) can be measured, standard methods for monitoring have been developed, and historical information exists for alligator populations in the Everglades. These attributes can be used as success criteria at different spatial and temporal scales and to construct ecological models used for predicting restoration effects. Here, we discuss Everglades alligator population status and its role in evaluating restoration success of the Southern Everglades.
Developing an index of alligator condition
Additional measurements including head length, hind foot length, chest girth, and tail girth have been taken. Using condition factor, we can compare:
Ultimately we will be able to relate alligator condition to other measures of alligator population health, such as growth and survival parameters (see the section--Ecological Correlates) and relative density (see the section--Alligator Survey Data).
The Everglades are a nutrient-poor environment and it is possible that alligators here have always been smaller than those of other regions.
We are concerned that human disturbance has worsened this trend.
We compared alligators captured from Everglades wetlands to alligators captured from lakes in north Florida and coastal areas of South Carolina. At a given length alligators from the Everglades weigh less than alligators from other locations.
Implication: Everglades alligators are not only smaller in length but also thinner than alligators of equal length in other geographical areas.
Everglades alligators are smaller compared to other geographical areas, but what about within different areas of the Everglades?
Implication: Alligators in the freshwater Everglades are in poorer condition than anywhere else. However, crocodiles in neighboring estuaries are in better condition. We hypothesize that these patterns are the result of low nutrients and a disturbed hydrology.
What else do we know about the health of alligator populations in the Everglades?
In addition to being thinner, alligators in the Everglades grow more slowly, take longer to reach sexual maturity, have smaller clutch sizes, and exhibit higher mercury levels than alligators from north Florida.
Implication: Performance measures for Everglades Restoration should reflect the importance of monitoring the health and condition of alligator populations.
Although there was little difference in the condition of alligators from different areas in the Everglades, there is a marked difference in relative density.
Implication: Relative density is an effective way to measure alligator abundance and can be used to evaluate restoration success.
Spatial and temporal patterns in alligator populations can be used to develop performance measures:
To help develop protocols for performance measures USGS and UF have begun a series of studies on alligators in the Everglades Ecosystem such as:
This research was supported in significant part by DOI's Critical Ecosystem Studies Initiative, a special funding initiative for Everglades restoration administered by the National Park Service; and in part by USGS's Florida Caribbean Science Center. Thanks to all of those who contributed data and time: Woody Woodward, Lindsey Hord, and Chris Tucker of the Florida FWC, Phil Wilkinson (retired) of the South Carolina Dept. of Natural Resources and everyone who participated in our alligator roundups.
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U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 15 January, 2013 @ 12:42 PM(TJE)