Evaluating risks associated with capture and handling of mule deer for individual‐based, long‐term research

Abstract

Capture and handling techniques for individual-based, longterm research that tracks the life history of animals by recapturing the same individuals for several years has vastly improved study inferences and our understanding of animal ecology. Yet there are corresponding risks to study animals associated with physical trauma or capture myopathy that can occur during or following capture events. Rarely has empirical evidence existed to guide decisions associated with understanding the magnitude of capture-related risks, how to reduce these risks when possible, and implications for mortality censoring and survival estimates. We used data collected from 2,399 capture events of mule deer (Odocoileus hemionus) via helicopter net-gunning to compare daily survival probabilities within a 10-week period centered on a capture event and evaluated how animal age, nutritional condition (body fat), and various handling methods influenced survival before, during, and following a capture event. Direct mortality resulting from

Shifts in risk sensitivity and resource availability alter fat stores for a large mammal following extreme winter conditions

“…As part of a long‐term, longitudinal study of mule deer in western, Wyoming, USA, we repeatedly sampled individuals each spring and autumn from March 2013 to December 2021 to evaluate how their nutritional condition (i.e., fat levels) during different seasons relate to a suite of life history and environmental characteristics. During this study, the population experienced unprecedented and harsh winter conditions during the 2016–17 winter, a winter much more severe than anything animals had experienced in nearly two decades (LaSharr et al, 2023). During this winter, animals were exposed to high snowpack and extended periods of low temperatures; and consequently, adult survival dropped substantially from what is typical for large ungulates (from survival of ~90% to 70%; LaSharr et al, 2023).…”

“…During this study, the population experienced unprecedented and harsh winter conditions during the 2016–17 winter, a winter much more severe than anything animals had experienced in nearly two decades (LaSharr et al, 2023). During this winter, animals were exposed to high snowpack and extended periods of low temperatures; and consequently, adult survival dropped substantially from what is typical for large ungulates (from survival of ~90% to 70%; LaSharr et al, 2023). Population density dipped significantly (~30%), providing us with a unique opportunity to test how density and severe winter conditions influence acquisition and allocation of resources by individuals (Figure 2).…”

“…Each year following that initial capture event, we recaptured surviving individuals and captured new individuals to maintain a sample size of 70 animals in mid‐March (i.e., spring) and early December (i.e., autumn) until December 2021. At the initial capture of any new animal, we extracted one incisiform canine to estimate age using cementum annuli (LaSharr et al, 2023). At each capture event, we collected data on nutritional condition, measured body mass and fit all animals with a GPS radiocollar programmed to take satellite fixes every 5 h from 2013 to Mar 2015, every 2 h from Mar 2015 to Mar 2018 and every 1h from March 2018 to the end of the study (Advanced Telemetry Systems, Isanti, Minnesota, USA; Telonics, Mesa, Arizona, USA; and Vectronic Aerospace, Berlin, Germany).…”

Spatial prey availability and pulsed reproductive tactics: Encounter risk in a canid–ungulate system

“…We captured adult (>1 year old) female mule deer using helicopter net gunning during April 2018and 2019(LaSharr et al, 2023. We fitted mule deer with GPS collars (Advanced Telemetry Systems Inc.…”

Behavior, nutrition, and environment drive survival of a large herbivore in the face of extreme winter conditions

“…Deer in the Wyoming Range experienced two particularly harsh winters (2016-2017 and 2018-2019) with extreme snowpack. During these winters, survival (~65% and 70%) fell far below what is typical for this population (~90%; LaSharr et al, 2023). These severe winters were extraordinary; animals in this population had never experienced winter conditions that harsh during their lifetime; thus, it presented a novel opportunity to evaluate whether animals can mitigate the effects of harsh environmental conditions by shifting behaviors and how dependent survival is on internal state.…”