Assessment of Translocation of Blanchard's Cricket Frog (Acris Crepitans Blanchardi) in Southeast Michigan

Rickard, Ariana, Endangered Species Update

Abstract

An entire population of Blanchard's cricket frogs (Acris crepitans blanchardi) threatened by construction, was translocated to three restored wetlands within the historic range of the species in the summer of 2004 and 2005. Working with the National Amphibian Conservation Center at the Detroit Zoo, state natural agencies and the developer, we moved about 1060 Blanchard's cricket frogs, a Michigan Species of Special Concern, from Lakewood Farms before housing construction began. This case study represents the first effort to track the effectiveness of translocations as a method of conserving cricket frogs in Michigan. I collected data on population structure and breeding success of the translocated populations of cricket frogs. I monitored nearby wild populations of cricket frogs to get baseline comparison data for the translocated frogs. Data on population size and breeding success were used to develop recommendations on amphibian translocation. Although initial breeding attempts were observed at all three release sites, and over 240 juvenile cricket frogs were seen at one of the translocation sites in August 2005, all translocated populations had declined rapidly by October 2005. The translocations apparently did not result in viable, self-sustaining populations of Blanchard's cricket frogs at any of the release sites. I recommend that no more cricket frog translocations occur until the causes of the decline is known and effectively removed at release sites. Conservation dollars and research should focus on habitat preservation and determining the causes of declining numbers of cricket frogs in the Midwest.

Resumen

Una poblacion entera de Acris crepitans blanchardi amenazada pot el desarrollo fue trasladada a tres pantanos restaurados en el area historica de las especies durante los veranos de1 2004 y 2005. Trabajando con el centro nacional de conservacion de amfibios en el Zoologico de Detroit, agencias de naturaleza estatales y el desarrollador, nosostros mudamos 1,060 ranas Acris crepitans blanchardi, una especie de Michigan de atencion especial, de Lakewood Farms antes que la construccion de casas comenzara. Este estudio representa el primer esfuerzo de monitorear la eficacia de los traslados como un metodo de conservacion para estas ranas en Michigan. Se recolecto data sobre la estructura poblacional, exito reproductivo de las poblaciones trasladadas de estas ranas. Tambien se llevaron a cabo conteos de las poblaciones silvestres cercanas de esta rana para tenet una comparacion de base con las ranas trasladadas. Datos del tamano de la poblacion, y exito reproductivo fueron usados para desarrollar recomendaciones de traslado de amfibios. A pesar que se observaron intentos iniciales de reproduccion y se observaron mas de 240 juveniles en las areas de traslado en agosto del 2005, para octubre del 2005 todas las poblaciones trasladadas habian disminuido rapidamente. Los traslados aparentemente no resultaron en poblaciones viables auto-sustentables de la rana Blanchard en ninguna de las areas de traslado. Recomiendo que no se hagan mas traslados de la rana Blanchard hasta que las causas de la disminucion se conozcan y se remuevan de manera efectiva de las areas de traslado. El dinero e investigacion para conservacion debe enfocarse en la preservacion de habitat y la determinacion de las causas de la disminucion del numero de ranas en el medio-oeste de los EE.UU.

Introduction

Since the late 1980s, there has been a global decline in population sizes and geographical ranges of a number of amphibians (Blaustein and Wake 1990). Possible causes for amphibian declines include habitat destruction and alteration, introduction of nonnative predators, pathogens, competitors, overexploitation, pesticides, pollution, acid rain, global warming, and UV radiation (Blaustein and Wake 1990). The root causes of many declines are unknown. The Blanchard's cricket frog was listed as a Species of Special Concern in Michigan in 1986 (Lee 1998). Surveys conducted in 1997 found 47 extant sites, so the species is too numerous to meet the state's criteria for threatened status (Lee 1998). In an attempt to increase the number of extant populations of cricket frogs in southeast Michigan, the National Amphibian Conservation Center initiated a translocation project to try to establish a self-sustaining population of cricket frogs in a restored wetland at the Detroit Zoo.

Usefulness of translocations as a management tool

Habitat loss appears to be the most significant factor contributing to amphibian declines (Wake 1991). Preserving critical habitat for threatened and endangered species is probably the best method for conserving species. Habitat preservation is not an option, however, when wildlife regulations do not mandate protection of habitat and when these laws are not properly enforced. One proposed method for mitigating habitat destruction is translocation, which is defined as the "intentional release of animals to the wild in an attempt to establish, reestablish, or augment a population and may consist of more than one release." (Griffith et al. 1989). Translocations are often promoted as tools for conserving amphibians, yet there is no consensus--and few data on the effectiveness of translocations as an amphibian conservation strategy (Marsh and Trenham 2001; Seigel and Dodd 2002). There are no generally accepted or widely used criteria for assessing the success or failure of translocations (Fischer and Lindenmayer 2000). Some measures that might be used to assess translocation success include population growth, and evidence of successful breeding (Towns & Ferreira 2001).

Here I report on a translocation that was used as a last resort to try to save a population of cricket frogs by introducing individuals into other wetlands before their breeding pond was destroyed to construct condominiums and houses. On …

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Publication information: Article title: Assessment of Translocation of Blanchard's Cricket Frog (Acris Crepitans Blanchardi) in Southeast Michigan. Contributors: Rickard, Ariana - Author. Magazine title: Endangered Species Update. Volume: 23. Issue: 1 Publication date: January-March 2006. Page number: 3+. © 2007 University of Michigan, School of Natural Resources. COPYRIGHT 2006 Gale Group.

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