Movement-based methods to infer parturition events in migratory ungulates

• Main Authors: Cameron, Matthew D., Joly, Kyle, Breed, Greg A, Parrett, Lincoln S., Kielland, Knut
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2018
• Subjects: Rangifer tarandus
• Online Access: http://hdl.handle.net/1807/91067; http://www.nrcresearchpress.com/doi/abs/10.1139/cjz-2017-0314

Long-distance migrations by ungulate species are a globally-imperiled natural phenomenon and conservation of them requires monitoring population vital rates. Satellite telemetry tracking is widely used for understanding the spatial distribution and movement of animals, especially migratory animals in remote environments. Recently, analytical methods have been developed to infer parturition events from movement data in multiple species that calve in isolation, but to date such methods have not been tested on animals that both migrate and spatially aggregate during calving. We applied 2 movement-based methods developed to infer parturition in non-migratory woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) to 241 reproductive seasons spanning 6 years of GPS data from migratory barren-ground caribou (Rangifer tarandus granti (Allen, 1902)). We compared results from both methods to data from aerial surveys of collared females during the calving period. We found that each movement-based method had ~ 80% overall accuracy to identify calving events, with inter-annual variation ranging from 61-100%. When we considered instances when the 2 analytical methods agreed on parturition outcome, the accuracy increased to 89% with an annual range of 73-100%. Using these methods, we identified marked inter-annual differences in peak calving dates and higher parturition rates than previously reported for this caribou herd. The successful application of these analyses to a migratory, gregarious ungulate suggests a broader applicability of the methodology. The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.