Research Update: The Status of Arboretum Frogs

Two young northern green frogs

Two young northern green frogs

This year marks the 35th anniversary of the Wisconsin Frog and Toad Survey (WFTS), led by the Wisconsin Department of Natural Resource. The first few years of the project were spent testing survey methods, and annual state-wide surveys commenced in 1984. Annual surveys have been conducted at the Arboretum and adjacent wetlands by experts and citizen scientists, marking it one of the most long-term and consistent datasets we have on Arboretum fauna.

The WFTS was created in response to concerns about declining statewide frog populations, especially northern leopard frogs, Blanchard’s cricket frogs, pickerel frogs, and American bullfrogs. Surveys are conducted from April 15 through July 15 at 10 sites, for a period of five minutes per site. The Arboretum sites include: Coyote Pond, Dunn’s Marsh, Gardner Marsh, Greene Prairie, HoNeeUm Pond, Lost City, Stevens Pond, Redwing Marsh, Teal Pond, and Wingra Springs.

Nine of the twelve Wisconsin frog and toad species are found at the Arboretum: the American bullfrog, American toad, boreal chorus frog, Cope’s gray treefrog, gray treefrog, northern green frog, northern leopard frog, spring peeper and the wood frog. The chorus frog is the most common species, heard every year in at least one site. Chorus frogs were common at most survey sites except HoNeeUm Pond, Stevens Pond, and Wingra Springs where they were heard infrequently. Other common species included the northern green frog, American toad, Cope’s gray treefrog, and northern leopard frog. All of these species have been heard in at least three of the last five years, with the exception of the northern leopard frog, which has been heard two of the last five years. In addition, all of these species were commonly recorded in statewide surveys, with the leopard frog showing a slight decline over the last 35 years.

Spring peepers, gray treefrogs, American bullfrogs and wood frogs were only heard in eight, five, four and one survey year(s) respectively. Although spring peepers were commonly recorded in statewide surveys, they have not been recorded at the Arboretum since 2010. When recorded, they were often heard at Dunn’s Marsh or Greene Prairie and only once at Redwing Marsh and Gardner Marsh. Gray tree frogs, although rare over the last 35 years, have been recorded at the Arboretum in three of the last five years. During this period they have been recorded at all survey sites except HoNeeUm Pond and Wingra Springs. Both of these species prefer moist forest and large woodlots adjacent to wetlands. Our recent efforts to restore the Teal Pond wetlands may provide adequate open wetland breeding habitat, in addition to Teal Pond itself. Keep your eyes and ears open for these species!

Another very uncommon species recorded near the Arboretum is the American bullfrog. This was one of the species that initiated the WFTS and remains a species of special concern in Wisconsin. It was last heard in 2011 at Dunn’s Marsh. Bullfrogs require permanent water such as lakes and large ponds with abundant emergent, submergent, and floating aquatic vegetation. Dunn’s Marsh and Lake Wingra fit this bill, but it may be difficult for bullfrogs to find large enough breeding habitat within the Arboretum boundaries. Look and listen for this species near Gardner Marsh and HoNeeUm Pond.

Wood frogs are relatively stable in the state; however, due their short breeding season they can be missed some years. This species was only recorded in 2012 at Teal Pond. Although this species is uncommon in south central and southwest Wisconsin, given the relatively recent record, it’s likely that wood frogs are found at low number in the Arboretum.

The Arboretum is dedicated to restoring and conserving habitat for these and many other native fauna. If you are out hiking the trails and hear or see one of our uncommon frog species please contact our ecologist, Brad Herrick.

To learn more about the survey and view statewide data at the Wisconsin Frog and Toad Survey website.