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Farm ponds as critical habitats for native amphibians

CHAPTER 4
Effects of Agricultural and Urban Land Use on Movement and Habitat Selection by Northern Leopard Frogs (Rana pipiens)

Brian C. Pember
University of Wisconsin-La Crosse
Department of Biology and River Studies Center
1725 State Street
La Crosse, Wisconsin 54601

Brent C. Knights, Melinda G. Knutson, and Shawn E. Weick
U.S. Geological Survey
Upper Midwest Environmental Sciences Center
2630 Fanta Reed Road
La Crosse, Wisconsin 54603

Abstract
Southeastern Minnesota is a landscape dominated by agriculture, with few natural wetlands apart from sloughs and oxbows associated with streams and rivers. However, many small farm ponds have been built to control soil erosion. Many species of amphibians breed in these ponds. Small cities in the region are expanding and communities along rivers are often adjacent to wetlands that are prime breeding areas for amphibians. Little is known about amphibian movement patterns and habitat selection in either agricultural or urban edge settings. The objective of this study was to compare the movement patterns and habitat selection of anurans in agricultural, urban, and natural ponds in southeastern Minnesota using radio-telemetry. After failing to track anurans with transmitters attached via external harnesses in 2000, we switched to surgical implantation of transmitters in 2001. We surgically implanted transmitters into the peritoneal cavity of 44 Northern Leopard Frogs (Rana pipiens) from three sites and tracked them from May to October 2001. Home range sizes and habitat use were investigated. R. pipiens at the agricultural site used areas of grassland and forests adjacent to the breeding ponds and these habitats represented most of their home ranges. At the natural and urban sites, R. pipiens selected wetland habitats representing only 2% of the available habitat. At the urban site, most frogs remained in a wetland adjacent to the industrial park. We suggest that the amount of high-quality habitat adjacent to the pond is an important influence on amphibian home range size and movement rates. The natural and urban sites were associated with high quality wetlands and grasslands, which provided abundant food, shelter, and over-wintering habitats and allowed smaller home ranges and movements. Frogs at the agricultural pond had to move more and required larger home ranges to meet the same needs. To support R. pipiens populations, managers should increase the amount and quality of amphibian feeding and wintering sites adjacent to breeding sites, reducing the hazards encountered and the energy required to move long distances.

Keywords: amphibian, habitat selection, radio telemetry, agriculture, Rana pipiens, home range, movement distance.