Amanda R. Goldberg: "Why have northern Idaho ground squirrel populations declined?"

Student Spotlight: Amanda R. Goldberg

My dissertation research is designed to test several hypotheses to explain why northern Idaho ground squirrel populations have declined. Northern Idaho ground squirrels (Urocitellus brunneus) were listed as threatened under the federal Endangered Species Act in 2000 (U.S. Fish and Wildlife Service 2000) and their range is restricted to Adams and Valley Counties in central Idaho. My research is part of a long-term research project funded by the U.S. Forest Service to test whether past population declines are due to fire suppression (and subsequent forest encroachment into meadows). I am testing predictions to evaluate 3 alternative hypotheses: (1) sylvatic plague, (2) climate sensitivity, and (3) nutrient limitation.

We work on 18 field sites located on private, U.S. Forest Service, and state (IDL) land within Adams County, ID. To address the plague hypothesis, we are conducting a field experiment to remove fleas (main vector of plague) from a subset of NIDGS colonies to investigate whether plague is present in NIDGS populations or in any small mammals that are sympatric with NIDGS. Furthermore, we collect fleas from a subset of animals we trap to both: 1) identify them to species, and 2) evaluate what factors influence flea abundance between years and sites. We are also using a vaccine on mice and chipmunks to document whether these 2 species are reservoirs for plague within NIDGS colonies. To address the climate sensitivity hypothesis we have been attaching radio collars with light-logger/temperature sensors to a subset of adult squirrels and locating their hibernacula burrows (northern Idaho ground squirrels hibernate for approximately 8 months each year). The light-loggers/temperature sensors enable us to document: 1) the exact date/time these squirrels immerge and emerge from their hibernacula, and 2) torpor bout length and body temperature which will allow us to estimate the energy used during hibernation. We will evaluate correlations between biotic habitat characteristics at hibernation sites and energy used by NIDGS to identify the site characteristics necessary for squirrel overwinter survival and how climate change may potentially affect those relationships. The nutrient limitation hypothesis is a more explicit, mechanistic version of the fire suppression hypothesis and suggests that shifts in plant community composition (from fire suppression) may be limiting certain key nutrients required by NIDGS and the limited availability of these key nutrients has caused the observed population declines. We have collected fecal samples from 13 sites that support northern Idaho ground squirrels and are using targeted amplicon sequencing to identify the species of plants in the diet of NIDGS (Valentini et al. 2009, Bybee et al. 2011). This will allow us to compare plant species composition found in the fecal samples to plant species composition and relative percent cover within the squirrels’ occupied habitat.

Our research involves close collaboration with 3 federal government agencies (U.S. Fish and Wildlife Service, U.S. Forest Service, and U.S. Geological Survey), Idaho Department of Fish and Game, and the University of Idaho. I have worked with 38 technicians over 5 field seasons and I have also been involved with the Doris Duke Conservation Scholars minority training program at the University of Idaho. For the past 3 field seasons, I have mentored 2-4 undergraduate students from under-represented groups join us in the field to learn more about of the professions of ecology and wildlife biology. We also had one undergraduate student spend most of the 2017 field season working alongside our field crew while also conducting his own senior thesis research. We are continuing to work with that student to help him analyze, present, and publish his results. Research from both my dissertation and the long-term restoration project should inform management decisions for the northern Idaho ground squirrel and hopefully help land management agencies implement management actions that will lead to its recovery and delisting.