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Publication #WEC268

Isolated Wetlands and Breeding Amphibians1

Taryn A. Sudol, Emma V. Willcox, and William Giuliano2

What are isolated wetlands?

Isolated wetlands, also known as seasonal, ephemeral, or vernal ponds, are small wetlands that form in depressions in the landscape. Isolated wetlands are not connected to permanent water bodies such as lakes, rivers, or streams. As a result, they hold water only temporarily, periodically drying out. The time during which a wetland holds water is called its hydroperiod. The hydroperiod varies from year to year and from wetland to wetland. A wetland's hydroperiod is influenced by its underlying geology, soil characteristics, depth, and size. Isolated wetland hydroperiod is also affected by amount of rainfall, evaporation rates, and degree of water loss (transpiration) from surrounding plants. Depending on these factors, a hydroperiod may last from weeks to years.

In Florida, isolated wetlands occur in a variety of habitat types including pine flatwoods, sandhill, scrub, dry prairie, and hardwood forests. They may be forested, with cypress or other large trees growing in or around the water (Figure 1). In other instances they occur in open areas with little or no tree canopy and are edged by herbaceous vegetation (Figure 2).

Figure 1. 

A forested isolated wetland. Credit: D. Cappaert, www.bugwood.org.


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Figure 2. 

An open isolated wetland. Credit: D. Cappaert, www.bugwood.org.


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Why are isolated wetlands important to amphibians?

Because they are temporary, isolated wetlands are often poorly understood and seen as little more than puddles. However, they provide a unique freshwater habitat for numerous aquatic animals and play a critical role in the life-cycles of many species. Isolated wetlands are of particular importance to a variety of pond-breeding amphibians (frogs and salamanders). Isolated wetlands typically do not contain predatory fish because they are inaccessible and dry periodically. Therefore, they provide extremely valuable habitat for amphibians that lack the defenses to co-exist with predatory fish. In Florida, isolated wetlands are used as breeding habitat by at least 28 species of amphibian (Table 1). Of these, 14 species are obligates, meaning they breed exclusively in isolated wetlands and nowhere else. The presence of isolated wetlands is essential for these species to breed successfully. The remaining species use isolated wetlands opportunistically and have the ability to breed elsewhere.

One obligate amphibian dependent on isolated wetlands for successful breeding is the frosted flatwoods salamander (Figure 3), a species found in pine flatwood habitats west of the Apalachicola/Flint drainage in the Florida Panhandle. The Federal Government considers this salamander a threatened species. A similar species, also dependent on these wetlands for breeding, is the reticulated flatwoods salamander. This species is found east of the Apalachicola/Flint drainage in north Florida and is listed as endangered by the Federal Government. During their September to December breeding season, these salamander species lay their eggs in the basins of dry isolated wetlands or in areas above the waterline. Contact with water triggers the eggs to hatch. Hatching occurs as rain begins to fill the wetlands and their water levels start to rise. The hatched larval young remain in the protected waters of the wetlands for 11 to 18 weeks. Therefore, for successful breeding, frosted and reticulated salamanders require a wetland hydroperiod of at least 11 weeks. In Florida, such a hydroperiod is reasonable because of the rainy weather that passes with the fall's cold fronts. However, these salamander species are unable to successfully produce offspring if isolated wetlands are not filled during their breeding season.

Figure 3. 

A frosted flatwoods salamander. Credit: J. Jensen.


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Why are the uplands surrounding isolated wetlands also important to amphibians?

While many amphibians use isolated wetlands for short periods to breed, they spend the majority of their life cycle in the surrounding uplands. The uplands adjacent to isolated wetlands are vital to non-breeding amphibians for foraging, burrowing, and dispersal. Juvenile amphibians regularly travel up to 1000 meters into the uplands to find suitable food and cover after leaving the wetland in which they were born. As adults, many will return to this wetland to breed. Therefore, isolated wetlands must be viewed in the context of the surrounding uplands when considering their importance to amphibians. These upland habitats are as crucial to the survival of many amphibian species as the wetlands.

How can isolated wetlands and their surrounding uplands be managed for amphibians?

Isolated wetlands and the lands that surround them are threatened by agricultural intensification, urban sprawl, invasive species, fire suppression, and ditching. Many isolated wetlands are ditched, drained, and filled for the purpose of creating new agricultural lands or subdivisions. This alters wetland hydroperiod, increases the risk of local flooding, and results in the loss of critical wildlife habitat. The ditching and draining of isolated wetlands should be avoided and existing ditches should be filled in an attempt to restore wetland hydroperiod. Other isolated wetlands are used for storm water retention. Storm water runoff adds pollutants to these sensitive systems and can severely damage water quality. In order to permit recreational fishing, isolated wetlands are also occasionally converted to more permanent wetlands in which predatory fish are stocked. These fish prey on the amphibians and their larvae and make the habitat unsuitable for future occupation.

There is little federal protection for isolated wetlands. Therefore, it is vital that landowners and land managers take the initiative to preserve and manage these valuable habitats. A native or restorable upland habitat buffer of at least 500–1000 meters or more should be delineated around each isolated wetland in order to provide sufficient breeding and non-breeding habitat for amphibians. If numerous wetlands exist in an area, attempts should be made to manage them as a group. Sufficient upland habitat should be retained around each wetland so that connections that permit amphibians to move to adjacent wetlands are maintained. A 500- to1000-meter upland habitat buffer should then be delineated around the entire wetland cluster.

In Florida, prescribed burning is typically the most important tool for managing isolated wetlands and their upland buffers. Both should be burned, depending on upland habitat type, every 1 to 10 years, preferably in late spring to early summer, or whenever wetlands are dry enough to carry a fire, the exception being wetlands surrounded by hardwood forest, since this habitat type is not typically burned on a regular basis. Burns help reduce excessive shrub encroachment and stimulate herbaceous growth in and around the wetlands and their associated buffers. When preparing to burn, care should be taken to ensure fire lines are not constructed close to wetland basins. These can have a negative impact by increasing water runoff into the wetlands and lead to an unnatural addition of nutrients or sediment. In addition, following heavy rains, fire lines may serve as conduits for movements of fish into isolated wetlands.

Heavy machinery and vehicle use should be avoided in and around isolated wetlands as it can lead to soil compaction or the breaking of the wetland basin's hardpan (a dense layer of soil impenetrable by water). Such damage can affect the amount of water the wetland is capable of holding and lead to alterations in wetland vegetation. In addition, standing dead trees, tree stumps, logs, and other woody debris occurring in the vicinity of an isolated wetland should be left as they provide important food and cover for many amphibian species. In situations where it is not possible to protect and manage all isolated wetlands in an area, priority should be given to those that occur in clusters, have varying hydroperiods, are surrounded by native or restorable habitat, and have known populations of imperiled species.

Tables

Table 1. 

Amphibians in Florida that utilize isolated wetlands.

Common Name

Scientific Name

Isolated Wetland Use

Frogs

   

Oak Toad

Bufo quercicus

Obligate1

Southern toad

Bufo terrestris

Opportunistic

Eastern narrowmouth toad

Gastrophryne carolinensis

Obligate

Cope's gray treefrog

Hyla chrysoscelis

Opportunistic

Green treefrog

Hyla cinerea

Opportunistic

Pine woods treefrog

Hyla femoralis

Obligate

Barking treefrog

Hyla gratiosa

Obligate

Squirrel treefrog

Hyla squirella

Opportunistic

Spring peeper

Pseudacris crucifer

Opportunistic

Southern chorus frog

Pseudacris nigrita

Obligate

Little grass frog

Pseudacris ocularis

Obligate

Ornate chorus frog

Pseudacris ornata

Obligate

Gopher frog

Rana capito

Obligate

Bull frog

Rana catesbiana

Opportunistic

Bronze frog

Rana clamitans

Opportunistic

Pig frog

Rana grylio

Opportunistic

Southern leopard frog

Rana sphenocephala

Opportunistic

Eastern spadefoot

Scaphiopus holbrookii

Obligate

Salamanders

   

Reticulated flatwoods salamander

Ambystoma bishopi

Obligate

Frosted flatwoods salamander

Ambystoma cingulatum

Obligate

Mole salamander

Ambystoma talpoideum

Obligate

Tiger salamander

Ambystoma tigrinum

Obligate

Two-toed amphiuma

Amphiuma means

Opportunistic

Dwarf salamander

Eurycea quadridigitata

Opportunistic

Striped newt

Notophthalmus perstriatus

Obligate

Eastern newt

Notophthalmus viridescens

Opportunistic

Southeastern slimy salamander

Plethodon grobmani

Opportunistic

Southern dwarf siren

Pseudobranchus axanthus

Opportunistic

1 Obligate refers to those species that breed exclusively in isolated wetlands.

Footnotes

1.

This document is WEC268, one of a series of the Wildlife Ecology and Conservation Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date September 2009. Reviewed August 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Taryn A. Sudol, student; Emma V. Willcox, graduate student; and William M. Giuliano, associate professor and Extension specialist; Department of Wildlife Ecology and Conservation, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.