Identifying elk and mule deer parturition events.
We inferred elk parturition events from GPS-collared elk between 2016
and 2019 using the rolling minimum convex polygon (MCP) method described
by Nicholson et al. (2019) to estimate large herbivore
parturition events based on localized movements. We assigned a
parturition event for elk as the first day a rolling MCP (based on a
24-hour window) decreased to <30 hectares or less for a
minimum of 120 hours. If these conditions were not met, we assumed the
elk did not give birth. We validated the method using independent elk
GPS locations with known birth dates and locations (N = 30) from
a previous study in the same area (Long et al. 2016). The mean
discrepancy between birth dates determined from field investigations by
Long et al. (2016) and birth dates predicted by the rolling MCP method
was 18 hours.
Parturition events of mule deer were determined either by 1) monitoring
GPS-collared adult females for localized movement and then searching the
area for neonates where a cluster of GPS locations had formed, 2) using
vaginal implant transmitters (details in Jackson et al. (2021)),
or 3) using the rolling MCP inference method (Nicholson et al.2019). For the rolling MCP method, we assigned a parturition event for
deer as the first day a rolling MCP (based on a 24-hour window) was
<15 hectares or less for a minimum of 120 hours. We validated
the rolling MCP method for 14 deer parturition events determined from
field investigations and found a mean discrepancy of 33 hours.