National Park Service

South Florida/Caribbean I&M Network (SFCN)

Amphibians Monitoring

Green Tree Frog in Everglades National Park (Credit USGS)
Green Tree Frog in Everglades National Park (Credit USGS).

Inventory Reports


The SFCN amphibians monitoring protocol is currently under development.



Amphibians comprise a large amount of the resident vertebrate biomass and generally are a strong intermediate link in the food web. Amphibians have been used as a biological indicator for many environmental variables and are sensitive to changes in breeding habitat quality, invasive species, and contaminants. At Virgin Islands National Park (VIIS), the native frog species are strongly tied to water resources for reproduction. The white-lipped frog (Leptodactylus albilabris) has a tadpole stage and the other two species, Antillean frog (Eleutherodactylus antilliensis) and whistling frog (Eleutherodactylus cochranae), utilize moist vegetation for egg laying with direct development to the froglet stage. Additionally, these frogs typically exploit the numerous tank bromeliads for daytime refugia. There are a number of exotic species that may be out competing and preying upon native fauna such as the Cuban treefrog (Osteopilus septentrionalis). In EVER and BICY, the pig frog, (Rana grylio), is a dominant anuran within the freshwater marsh lands and makes up a large amount of the vertebrate biomass. It is both a prey source and a major predator. The pig frog life cycle (eggs-tadpoles-adults) is strongly related to marsh hydrology. Shifts in pig frog population structure have been shown to be related to water management. Additionally, pig frogs bioaccumulate mercury and currently are being monitored by the State of Florida (FWRI) for mercury levels. Previous amphibian studies within these parks have documented exotic species immigration and shifts in population structures of native species due to exotic species. Community composition of the amphibian species community has been related to habitat type within these park units.

Monitoring Objectives

  • What are the status and trends in the distribution, abundance (or occupancy), and community composition of native and non-native amphibian species?
  • What are the status and trends in pig frog demographic structure, especially in relation to water levels and CERP/MOD Waters Everglades restoration?
  • What are the status and trends in mercury accumulation in pig frogs?

Status & Trends

Monitoring for this vital sign has not commenced. However, inventory reports are available under our Reports page.


SFCN plans to develop an “Amphibians” protocol to monitor amphibians at BICY, EVER, and VIIS. BISC and SARI are deferred. The protocol will build on the inventory work already completed. The protocol is further detailed in Appendix P. The primary parts of the protocol include:

  1. At VIIS, EVER and BICY amphibians will be monitored in areas near roads and trails with Visual Encounter Surveys (VES), call surveys and tree pipes by developing a proportion of area occupied (PAO) methodology similar to the ARMI inventory protocol methods used in these parks (Rice et al., 2004, 2005a, 2005b) . Current funding levels are insufficient to attempt monitoring away from roads and trails, especially in areas accessible only by helicopter.
  2. In EVER and BICY SFCN will collect grab samples of pig frogs to determine size structure of populations, sex ratios, and juvenile to adult ratios. This sampling will build upon previously existing research.
  3. SFCN will coordinate with the State of Florida mercury monitoring program. SFCN goal is to include pig frogs from EVER and BICY in the states regional assessments.

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Last Updated: March 28, 2017 Contact Webmaster