Northern Idaho ground squirrel population monitoring progress report for the 2011 field season

Publication Type:

Report

Authors:

Wagner, Betsy; Diane Evans Mack

Source:

Threatened and Endangered Species Project E-28-9, Idaho Department of Fish and Game, Boise, p.18 (2011)

Call Number:

U11WAG01IDUS

Keywords:

northern Idaho ground squirrel, Spermophilus brunneus brunneus, Urocitellus brunneus

Abstract:

Population monitoring of the federally threatened northern Idaho ground squirrel (Urocitellus brunneus brunneus, formerly Spermophilus brunneus brunneus [Helgen et al. 2009]) continued in 2011. We conducted capture-mark-recapture at 4 of 5 intensive monitoring sites and estimated numbers at these sites with either a POPAN model or Closed Model with Heterogeneity (2 mixtures) run in Program MARK. We captured 140 individual adults and yearlings, substantially more than in 2010 but similar to 2009. We live-trapped at 3 additional sites adjacent to 2010 habitat treatments to collect fecal samples for diet analyses, capturing 36 individuals. We explored a new approach to surveying the remaining 52 known sites as a transition to a more systematic long-term monitoring approach. We conducted line transect distance sampling at a stratified random sample of sites. We stratified by density, selected 40 sites, and surveyed each site 3 times. We used program DISTANCE v6.0 to estimate population size by stratum. We conducted post-hoc analyses of the line-transect data based on a random sample of transect lines, not sites. We identified a desired total annual effort of 200 km and selected 10 random samples of lines achieving that effort. We repeated the DISTANCE analyses on each of these 10 samples. The population estimate N from a single visit (replicate 2) of our truncated original sample was 1,333. This was lower than our estimates from 2010 and 2009 using counts of squirrels detected on surveys. Average cluster size was 1.04 and effective strip width 20 m. From all methods combined, northern Idaho ground squirrels NIDGS occupied 54 of the 59 known sites in 2011. New locations were discovered adjacent to three known sites. Columbian ground squirrels and badgers were detected at 34 and 16 sites, respectively. The line-transect dataset will continue to be analyzed with the overarching goal of establishing a long-term sampling protocol for the NIDGS population.