Butler's Garter Snake Field Research

Craig Berg, Milwaukee County Zoo aquarium and reptile curator
Gary S. Casper, Ph.D. - associate scientist, University of Wisconsin-Milwaukee Field Station   
Timothy Vargo -  research coordinator, Urban Ecology Center, Milwaukee, Wis.

The Butler’s garter snake is an endangered species that is restricted to southeastern Wisconsin.  In 2007, the Wisconsin Department of Natural Resources (DNR) brought together developers, landowners, the Milwaukee County Zoo and other conservation organizations to develop a management plan for this species. This plan identified numerous gaps in our knowledge that were crucial the development of a successful plan.  As a result, the Zoo joined hands with the Urban Ecology Center at Milwaukee’s Riverside Park to seek answers to several questions.  What is the dispersal distance of the state-threatened Butler’s garter snakes? What is the population density of the snakes in Riverside Park? How fast do they grow?  These studies involve radio-tracking, finding and capturing snakes and marking them for individual identification.  Hundreds of hours were involved and several additional seasons of work will be needed to adequately address these issues.

The investigators will assist the Urban Ecology Center (UEC) with development of a long-term citizen-based monitoring program of Butler’s garter snakes in Riverside Park and the surrounding areas. This will include:

  • annual snake mark/recapture surveys using plywood cover boards, and
  • the tracking of individual Butler’s garter snakes to determine life-history parameters and population trends using a harmonic location device. 

The Milwaukee County Zoo will assist the UEC with its programs in an advisory and support capacity to yield the following results:

  1. Citizen volunteers will be trained in snake mark/recapture techniques, safe trapping methods, identification, radio-tracking techniques and data collection and analysis. Presence data will be entered into the public Wisconsin Nature Mapping database.
  2. Portions of the research will be submitted to peer-reviewed academic journals.
  3. Project personnel will present portions of this research at conferences and symposia.
  4. Data collected will be used by the Milwaukee River Working Group, a coalition of organizations including the River Revitalization Foundation, Friends of Milwaukee’s Rivers, UEC, riparian landowners and other community groups that serve as an advisory panel for land use along the river. Data collected will also help steer planning and implementation of the UEC’s 100-year management plan for Riverside Park and will contribute to a conservation plan of the state-threatened Butler’s garter snake by the Butler’s garter snake Stakeholder Working Group (PHVA).

A grant of $5,000 has been received from the Wisconsin DNR Citizen-based Monitoring Partnership Program for this work.  Zoological Society of Milwaukee funds have been combined with this grant for equipment, data analysis, field-worker stipends and program administration.

Update April 2009 from Craig Berg: “Due to heavy rains in June 2008 in Wisconsin, the field work was abbreviated compared to years past. Equipment for locating the garter snakes in the field has been obtained. This should help to determine what types of sites are used for overwintering.”