Use of Amphibian Communities as Indicators of Restoration Success in the Everglades

Authors

Amanda N. Rice, J. Hardin Waddle, Kenneth G. Rice, and Frank J. Mazzotti

Introduction

The Comprehensive Everglades Restoration Plan (CERP) requires the use of indicator species to measure the success of restoration efforts. The Everglades amphibian community is an ideal indicator because amphibians are present in all habitats and under all hydrologic regimes in the Everglades. The hydropattern in the Everglades, the amphibian biphasic life-cycle, and individual species requirements are all responsible for the distinct pattern of amphibian communities across habitats.

We have developed two major projects that use amphibian communities as ecosystem restoration indicators. The first project, completed in 2003, was an inventory of amphibian communities in Everglades National Park, Biscayne National Park, and Big Cypress National Preserve. This project established baseline data for amphibian communities in the study areas and elucidated habitat and hydrologic associations of the amphibian species. The second project, currently underway, is investigating amphibian communities across the hydrologic gradient in the Everglades. This project will define and measure the membership and area occupancy of amphibian communities in habitats with different hydropatterns, thus allowing managers to evaluate Everglades restoration efforts, establish restoration targets, and compare restoration alternatives.

Florida Cricket Frog Southern Leopard Frog
Florida Cricket frog (Acris gryllus) on lily pad in WCA 3A. Southern Leopard Frog (Rana sphenocephala)

Methods

Both projects used randomly selected plots to obtain data on amphibians. Three sampling methods were used to inventory amphibians, including Anuran Vocalization Surveys, Visual Encounter Surveys, and Trapping. Vocalization surveys and Visual encounter surveys are conducted at night.

Anuran Vocalization Surveys

At each randomly chosen plot, frogs and toads heard vocalizing for 10 minutes were noted in categories of abundance and frequency.

Abundance of vocalizing frogs and toads were put into one of five possible categories:

  • One individual calling
  • 2-5 individuals
  • 6-10 individuals
  • > 10 individuals, or Large chorus

Frequency of vocalizing frogs were put into one of three categories:

  • Occasional
  • Frequent
  • Continuous

Visual Encounter Surveys

At each randomly chosen plot, amphibians are surveyed for 30 minutes.

Amphibians detected are identified to species.

Amphibians are captured if possible, measured and weighed.

Trapping

Amphibians were trapped using two types of funnel traps: crayfish and minnow.

In addition, PVC pipe refugia were used to trap treefrogs.

Checking PVC pipe refugia in WCA 3B PVC pipes with crayfish trap attached
Checking PVC pipe refugia in WCA 3B PVC pipes with crayfish trap attached

Inventory of Amphbian Communities in Everglades National Park

This study was conducted from 2000 to 2003. Goals of the project were to create a georeferenced inventory of amphibian species, use new analytical techniques to estimate proportion of sites occupied by each species, look for any signs of amphibian decline (missing species, disease, die-offs, etc.), and establish a protocol that could be used for future monitoring efforts.

Results from our amphibians surveys and trapping throughout Everglades National Park were used to estimate the proportion of sites or proportion of area occupied (PAO) by each amphibian species in each habitat.

Green Treefrog (Hyla cinerea)

Green Treefrog (Hyla cinerea)


Months in 2001 during which Hyla cinerea was detected by VES methods and vocalization

Month VES Vocalization
Jan X
Feb X
Mar X X
Apr X X
May X X
June X X
July X X
Aug X X
Sept X X
Oct X
Nov X
Dec X

Number of sites sampled, sites at which Hyla cinerea was detected, and the na´ve site occupancy rate by habitat

Habitat Number of Sites Number of Sites with Detection Naive Occupancy Rate PAO Estimate
Cypress 16 13 81.3% 90.15%
Hammock 14 12 85.7% 95.62%
Mangrove 16 7 43.8% 48.82%
Pineland 17 15 88.2% 95.44%
Rocky Glades 18 16 88.9% 99.09%
Slough 29 29 100.0% 100.00%
Borrow Pit/ Canal 4 3 75.0% N/A
Building/ Road 4 3 75.0% N/A
Total 118 98 83.1% 88.23%

Results of this study are in report form and available on CD-ROM:

Rice, K.G., J.H. Waddle, M.E. Crocket, B.M. Jeffery, and H.F. Percival., 2004. Herpetofaunal Inventory of the National Parks of South Florida and the Caribbean: Volume 1. Everglades National Park. U.S. Geological Survey, Open-File Report 2004-2005, Fort Lauderdale, Florida.

Use of Amphibian Communities as Indicators of Restoration Success Across Hydrologic Gradients

In this study, amphibian communities are being investigated in four habitats with different hydropatterns. This study will produce a model of amphibian community patterns across hydrologic gradients and will allow managers to measure restoration success.

Hydropattern of each site in this study. Each site contains five plots

Site Number of Days With Standing Water
Main Park Road 95*
Context Road 201*
WCA 3B 342*
WCA 3A 365*
* 10 year average
Pig Frog

Pig frog (Rana grylio)

Species Number Trapped Trap Type Site*
Green treefrog Hyla cinerea 102 PVC MPR, CR, 3A, 3B
Squirrel treefrog Hyla squirella 81 PVC MPR, CR
Squirrel treefrog Hyla squirella 1 Minnow CR
Leopard frog Rana sphenocephala 6 Minnow CR
Pig frog Rana grylio 1 (adult) - 4 (tadpoles) Crayfish 3A, 3B
Oak toad Bufo quercicus 1 Minnow MPR
Peninsular newt Notophalmus viridescens priapicola 1 Crayfish 3A
Greater siren Siren lacertina 7 Crayfish 3A, 3B
Florida green water snake Nerodia floridana 4 Crayfish 3A
Striped crayfish snake Regina alleni 1 Minnow MPR
Green anole Anolis carolinensis 3 Minnow CR
* MPR = Main Park Road site, CR = Context Road site, 3A = WCA 3A site, and 3B = WCA 3B site
Plot 20 in WCA 3B

This is plot 20 in WCA 3B. Here we listen for frog calls, visually search for amphibians, and trap using crayfish traps and PVC pipes. Frogs commonly heard here are green treefrogs (Hyla cinerea), pig frogs (Rana grylio), Florida cricket frogs (Acris gryllus), and southern leopard frogs (Rana schenocephala).

Siren Siren

The purpose of trapping at sites 3A and 3B is to catch aquatic salamanders such as the greater siren (Siren lacertina). The greater sirens captured are measured, weighed and released.

Citation

Rice, A.N., J.H. Waddle, K.G. Rice, and F.J. Mazzotti. (2004, December). Use of Amphibian Communities as Indicators of Restoration Success in the Everglades. Poster presented at the National Conference on Ecosystem Restoration, Orlando, Florida.