Implementing a novel movement-based approach to inferring parturition and neonate caribou calf survival

February Implementing a novel movement-based approach to inferring parturition and neonate caribou calf survival Maegwin Bonar 0 1 E. Hance Ellington 0 1 Keith P. Lewis 0 1 Eric Vander Wal 0 1 0 Department of Biology, Memorial University of Newfoundland , St. John's, Newfoundland and Labrador , Canada , 2 School of Environment and Natural Resources, Ohio State University , Columbus , Ohio, United States of America, 3 Department of Fisheries and Oceans , St. John's, Newfoundland and Labrador , Canada 1 Editor: Daniel Barry Hardy, University of Western Ontario , CANADA In ungulates, parturition is correlated with a reduction in movement rate. With advances in movement-based technologies comes an opportunity to develop new techniques to assess reproduction in wild ungulates that are less invasive and reduce biases. DeMars et al. (2013, Ecology and Evolution 3:4149?4160) proposed two promising new methods (individual- and population-based; the DeMars model) that use GPS inter-fix step length of adult female caribou (Rangifer tarandus caribou) to infer parturition and neonate survival. Our objective was to apply the DeMars model to caribou populations that may violate model assumptions for retrospective analysis of parturition and calf survival. We extended the use of the DeMars model after assigning parturition and calf mortality status by examining herdwide distributions of parturition date, calf mortality date, and survival. We used the DeMars model to estimate parturition and calf mortality events and compared them with the known parturition and calf mortality events from collared adult females (n = 19). We also used the DeMars model to estimate parturition and calf mortality events for collared female caribou with unknown parturition and calf mortality events (n = 43) and instead derived herd-wide estimates of calf survival as well as distributions of parturition and calf mortality dates and compared them to herd-wide estimates generated from calves fitted with VHF collars (n = 134). For our data, the individual-based method was effective at predicting calf mortality, but was not effective at predicting parturition. The population-based method was more effective at predicting parturition but was not effective at predicting calf mortality. At the herd-level, the predicted distributions of parturition date from both methods differed from each other and from the distribution derived from the parturition dates of VHF-collared calves (logranked test: ?2 = 40.5, df = 2, p < 0.01). The predicted distributions of calf mortality dates from both methods were similar to the observed distribution derived from VHF-collared calves. Both methods underestimated herd-wide calf survival based on VHF-collared calves, however, a combination of the individual- and population-based methods produced herd-wide survival estimates similar to estimates generated from collared calves. The limitations we experienced when applying the DeMars model could result from the shortcomings in our data violating model assumptions. However despite the differences in our caribou - Data Availability Statement: The minimal underlying data set necessary for replication of this study is available within the paper and its Supporting Information files. Funding: Funding for this study was provided by the Natural Science and Engineering Research Council of Canada, The Newfoundland and Labrador Research Development Corporation and the Atlantic Computational Excellence Network Canada Fellowship Program. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. systems, with proper validation techniques the framework in the DeMars model is sufficient to make inferences on parturition and calf mortality. Introduction Significant life history events correspond with a change in movement behavior in wildlife species. For example, parturition in ungulates is generally associated with a steep reduction in movement rate [ 1 ] and movement rate slowly increases as offspring become more mobile. Due to recent advances in statistical techniques and GPS technologies [ 2,3 ], researchers have been able to not only estimate the timing of parturition events using movement data [4?7] but also to assess calf survival based on the movements of adult female caribou [ 8 ]. However, the transferability of novel methods may be limited by assumptions from the system in which the model was built. Recently, a promising advance in estimating parturition and neonate calf survival using movement data of adult females was developed for sedentary caribou (Rangifer tarandus caribou) herds in central British Columbia, Canada by DeMars et al. [ 8 ] (hereafter ?the DeMars model?). Across their circumpolar distribution caribou exhibit variation in their movement behaviors, which may differ from those, exhibited in central Britis (...truncated)