Abundance and Movements of Mammals on the INL Site


Distribution, Abundance and Movements of Mammals on the Idaho National Laboratory Site

Mammals play functional roles in sagebrush steppe ecosystems, and many species are sensitive to anthropogenic disturbance. Data on presence, absence, and abundance of small mammals, and detailed data on movements of large mammals, provide land managers with critical information on ecological interactions between mammals and their environment. Such information is necessary for understanding past effects of anthropogenic disturbance on mammals and for predicting effects of future development, as well as for minimizing the negative effects of development on mammals. Although previous presence-absence surveys have been conducted on the INL Site for a variety of mammalian species, results of those surveys have not yet been compiled into a format that facilitates species-specific study of relationships between mammals and their environment at that site. In addition, data necessary to understand large-scale patterns of movement and resource selection by large mammals on the INL have never been obtained.

The overall goal of our project is to obtain presence-absence data and, where possible, abundance data for both common and rare small mammals on the INL Site, and to document landscape-scale patterns of movement and resource selection by elk (Cervus elaphus) at that site. Results of our study will be integrated into the Conservation Management Plan for the INL Site, and will provide the Department of Energy with important information for environmental planning purposes. In addition, our results will provide information useful for managers desiring to minimize depredation of crops surrounding the INL Site by large herbivores, and will provide insights into the potential role of large mammals in distributing environmental contaminants both on and off of the study site.


  • Review all previously-published literature on small mammal research conducted on the INL Site, and compile species-specific results into a searchable database

  • Conduct trapping surveys to determine presence/absence of both common and rare small mammals in the Development Zone

  • Use ultrasonic detection equipment to conduct “digital mist-netting” of bats in the Development Zone

  • Fit 20 elk with GPS collars to determine (1) the extent to which critical habitat (e.g., calving grounds) for that species occurs within the Development Zone; and (2) when, where, and to what extent elk move between the INL Site and surrounding agricultural lands.


Accomplishments through 2009

  • All previously-published data for small mammals on the INL was reviewed, and a database was compiled that included the date and title of each publication, the journal and page numbers in which it occurred, authors of the publication, time period in which the research was conducted, any specific information provided about the location of the research, and which species were trapped, observed, etc.

  • Trapping surveys were conducted for small mammals in the Development Zone between May and August, resulting in the capture of 634 individuals of 5 different species

  • For each animal captured, location, sex, and weight were recorded

  • Initial preparations were for made for conducting elk research in the Development Zone in early 2010.



Results from small mammal trapping surveys conducted in the Development Zone during spring and summer of 2009 are summarized in the following table..

Number, percent female, and weight of 5 species of small mammals captured during trapping surveys in the Development Zone on the INL Site during spring and summer of 2009.




Weight (g)






Dipodomys ordii





Perognathus parvus





Peromyscus maniculatus





Reithrodontomys megalotis





Tamias minimus











Plans for Continuation
There are several key objectives of this project that are planned for completion in 2010:

  • We will again conduct small mammal trapping surveys in the Development Zone during spring and summer, but we will alter our methods to focus on rare species. In particular, our trapping efforts will be focused on shrews, voles, and the northern grasshopper mouse.

  • We will coordinate efforts with Bill Doering to use ultrasonic bat detection equipment placed near caves in the Development Zone to determine which bat species are present in that area.

  • We will capture 20 elk in the development zone and fit them with GPS collars programmed to collect hourly locations from March-November of 2010.

  • We will analyze elk location data to determine where critical calving grounds on the INL are located, identify general patterns of resource selection and movement by elk on the INL, and determine the degree to which elk move between the INL and surrounding agricultural lands.

Publications, Theses, and Reports
This project is ongoing, and no papers or reports have been completed at this time. Nevertheless, several peer-reviewed publications and a final report stemming from this work are planned following its completion in 2010. In addition, our first year of trapping data has already been integrated into the ESER Natural Resources Data Management System in an effort to provide easy access that will support the CMP.