On October 26, USGS Patuxent researchers Linda Weir, Priya Nanjappa, Amy Goodstine (Frogwatch Coordinator) and Robin Jung will be heading to a television studio for a taping session of a Montgomery County TV program (Channel 19) entitled, "The Earth Speaks". Some of the issues, questions, talking points, and script outline for the show appear below in the attached document. Post production visuals for the show (appropriately identified with our USGS emblem) will also be provided by the group. Since the schedule for the airing of the show has not been set, Dr Jung indicated she will provide additional information as that time becomes more clearly defined.

PDF File for Show

Work of Patuxent's Runge and Cornell Collaborators Highlighted in The Chronicle of Higher Education

The work of USGS scientist Michael Runge and collaborators at Cornell University is receiving positive media attention, having been highlighted recently in The Chronicle of Higher Education ("Trapped by Evolution," October 18, 2002, pages A19-A20). In an article in Trends in Ecology and Evolution, Drs. Martin Schlaepfer and Paul Sherman, with Dr. Runge, propose the term "evolutionary trap" to describe cases where anthropogenic disturbances disrupt evolved behaviors of other organisms, with negative consequences to populations of those organisms. This phenomenon, which links the fields of behavioral ecology and conservation biology, may be a ubiquitous, but hitherto poorly recognized, mechanism by which humans cause species' decline. In a forthcoming article in Ecology, Drs. Sherman and Runge explore the role this mechanism might have played in the collapse of a threatened species, the Northern Idaho ground squirrel.

Schlaepfer M.A., M.C. Runge, and P.W. Sherman. 2002. Ecological and evolutionary traps. Trends in Ecology and Evolution 17(10):474-480.

Abstract

Organisms often rely on environmental cues to make behavioral and life-history decisions. However, in environments that have been altered suddenly by humans, formerly reliable cues might no longer be associated with adaptive outcomes. In such cases, organisms can become ‘trapped’ by their evolutionary responses to the cues and experience reduced survival or reproduction. Ecological traps occur when organisms make poor habitat choices based on cues that correlated formerly with habitat quality. Ecological traps are part of a broader phenomenon, evolutionary traps, involving a dissociation between cues that organisms use to make any behavioral or life-history decision and outcomes normally associated with that decision. A trap can lead to extinction if a population falls below a critical size threshold before adaptation to the novel environment occurs. Conservation and management protocols must be designed in light of, rather than in spite of, the behavioral mechanisms and evolutionary history of populations and species to avoid "trapping" them.

Publications, continued

Sherman, P.W. and M.C. Runge. 2002. Demography of a population collapse: the Northern Idaho ground squirrel (Spermophilus brunneus brunneus). Ecology 83(10):2816-2831.

Abstract

We studied the demography of a population of Northern Idaho ground squirrels (Spermophilus brunneus brunneus) in Adams Co., Idaho. The population was completely censused yearly from 1987 to 1999, during which time it declined from 272 to 10 animals. The finite population growth rate, based on a Leslie matrix model of average life-history parameters, was only 0.72 (i.e., significantly <1.0). Growth rate was more sensitive to proportional changes in juvenile female survival than to any other single life-history parameter. Comparisons with self-sustaining populations of closely related ground squirrel species revealed that juvenile survival and breeding rates of yearling females were anomalously low. We believe that the ultimate cause of the population's collapse was inadequacy of food resources, particularly seeds, due to drying of the habitat and changes in plant species composition, likely the result of fire suppression and grazing. No "rescue" by immigration occurred, probably because S. b. brunneus seldom disperse long distances and fire suppression has allowed conifers to encroach on inhabited meadows, shrinking them and closing dispersal routes. The proximate cause of the population's collapse was mortality of older breeding females, which reduced the mean age of breeders. Younger females had lower average pregnancy rates and litter sizes. To place our results in context we developed a new, general classification of anthropogenic population declines, based on whether they are caused by changes in the means of the life-history parameters (blatant disturbances), their variances (inappropriate variations), or the correlations among them (evolutionary traps). Many S. b. brunneus populations have disappeared in recent years, apparently due to blatant disturbances, especially loss of habitat and changes in food-plant composition, resulting in inadequate prehibernation nutrition and starvation overwinter. In addition, our study population may have been caught in an evolutionary trap, because the vegetational cues that could potentially enable the animals to adjust reproduction to the anticipated food supply no longer correlate with availability of fat-laden seeds.

HiLites Contact: B.H. Powell, USGS Patuxent Wildlife Research Center, 301-497-5782

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