Post-translocation dynamics of black-tailed prairie dogs (Cynomys ludovicianus): A successful conservation and human-wildlife conflict mitigation tool

Translocation, processing, and release We translocated prairie dogs from undesirable locations to two inactive prairie dog colonies (Charlie’s and Charlie’s South) that had previously experienced plague events within the Fort Hale Bottom prairie dog complex at the Lower Brule Sioux Indian Reservation in central South Dakota, USA. At the time of capture, prairie dogs were weighed to a tenth of a gram and implanted with a passive integrated transponder (PIT: AVID® Identification Systems, Norco, CA) tag for individual identification. Sex and age classes (juvenile and adult) were recorded as determined by weight and appearance (Hoogland 1995). Prairie dogs were released into burrows to maintain the coteries of the source colonies. The spatial orientation of neighboring coteries from the source colonies was also maintained. Groups typically contained 1 adult male and the remaining individuals were adult females and juveniles of both sexes. Recapture To sample the population at the release site; animals were recaptured at approximately 1 month and 1-year post-translocation at both release sites to determine retention and to determine if, and how far, animals moved from where they were initially released. The prairie dogs translocated in 2017 (Charlie’s colony) were recaptured September 26–28, 2017, at 37–39 days (recapture 1) and August 16–18, 2018, at 361–363 days (recapture 2) post-initial release. The prairie dogs translocated in 2018 (Charlie’s South colony) were recaptured August 23–25, 2018, at 40–42 days (recapture 1) and August 21–23, 2019, 405–407 days (recapture 2) post initial release. Traps with individual identification tags were set in a 10 m x 10 m grid across the entire colony where active prairie dog presence was visible. All trap locations within the grid were recorded. Captured animals were weighed, scanned for PIT tag identification number, marked with permanent marker, and released into the nearest burrow. All individuals that did not have PIT tag identifiers were marked with permanent marker, and sex and age were recorded. During subsequent trapping days, traps that contained marked individuals were released immediately. Analyses Distance moved post-release To understand if prairie dogs remained within their coterie as released or if they moved within the colony and established new territories, we measured the distance from where each prairie dog was initially released to their 1-month location and from their 1-month location to their 1-year location in ArcGIS v10.7.1. Furthermore, we compared the average distance between recapture locations to the diameter of small (0.05 ha), average (0.32 ha), and large (1.01 ha) territory sizes (Hoogland 2006b) and identified the percent of prairie dogs that were recaptured within the given territory size across each time step. We used Chi-square goodness-of-fit tests to determine if the proportion of prairie dogs that moved in each territory size differed between the Charlie’s and Charlie’s South colonies. We assumed that the distance between release and 1-month locations and 1-month and 1-year locations could provide a representation of the territory size of their coteries. Effect of coterie dynamics on retention To determine if the number of individuals in a coterie and the age structure and sex composition of the coterie influenced retention, a binary response variable, we used generalized linear mixed models (GLMM; Jamil et al. 2013) in Program R statistical base package (R Development Core Team, Version 3.6.3 2020). Individuals were released with the coterie they were captured with, therefore, we included coterie as random effect to account for potential effects of social structure that might differ by coterie and not be explained by our predictor variables. In addition to sex (male or female), age (juvenile or adult), and the group size of the coterie, we also included weight (g), burrow release type (single or double openings), and release site (Charlie’s or Charlie’s South) as fixed effect predictor variables to account for additional variation. We also created a combined variable of sex and age (adult male or female and juvenile male or female). We did not allow these combined age-sex variables to enter the same model as age or sex because of the inherent correlation between them. No other variables were correlated at > 0.6. Rather than run all possible model combinations which can result in overly complicated models with reduced biological meaning, we used expert opinion to determine biologically relevant models based on the biology of the system. We also included a global and a null model with just the random effect and intercept. We calculated AICc because of small sample size, ΔAICc, AICc weight, and log-likelihood to rank models (Burnham and Anderson 2002). Models within 2 AICc of the top model were considered indistinguishable from each other (Burnham and Anderson 2002). Once top models were identified, we calculated model average parameter estimates with 95% confidence intervals (Arnold 2010). Parameters whose confidence intervals did not overlap zero were determined to be important predictors or prairie dog recapture success. We repeated this process for 1-month and 1-year post-release.