LB 11-140 - Complementary definitions of calving grounds improve identification of critical habitat for migratory caribou

Background/Question/Methods:

Neonate survival is a key component of population dynamics, and protecting areas where species aggregate to give birth can contribute to increased neonate survival. In addition, due to limited mobility of neonates, areas used during the first weeks after birth are also critically important to neonate survival. This is especially true for species that tend to aggregate births spatially, such as barren-ground caribou (Rangifer tarandus groenlandicus), a highly social animal that is particularly sensitive to human disturbances. Identifying areas used by females and their neonates using a consistent, conservative, and reproducible method is vital for conservation purposes. We compared four quantitative, reproducible methods for determining annual calving grounds derived from an analysis of telemetry data from 142 GPS-collared female caribou from the Qamanirjuaq herd in Nunavut, Canada, monitored between 2013 and 2020. The methods variously rely on individual identification of calving timing from sudden slowing of animal movements, time to recovery of pre-natal movement rates, and/or on overall area and mean displacement rates of all collared animals in a given year.

Results/Conclusions:

While all methods gave broadly similar results, the method that combined herd-level movement rates and overall spatial extents was most robust to variability in sample size. This is an important consideration for the management of sensitive species as it provides a guideline for minimizing invasive capture and collaring. Furthermore, this method allows for historical comparisons across years where sampling sizes have varied. Thus, the analysis of GPS data can provide a rigorous estimation of the duration of the calving season and the extent of the annual calving grounds, which is valuable for effective conservation measures and identification of critical habitat for this and other at-risk species. Furthermore, a consistent approach to identifying annual calving grounds allows us to analyze the causes and consequences of shifting space use as a wide-ranging animal adapts to a changing climate.