A seasonal pulse of ungulate neonates influences space use by carnivores in a multi‐predator, multi‐prey system

Abstract

The behavioral mechanisms by which predators encounter prey are poorly resolved. In particular, the extent to which predators engage in active search for prey versus incidentally encountering them has not been well studied in many systems and particularly not for neonate prey during the birth pulse. Parturition of many large herbivores occurs during a short and predictable temporal window in which young are highly vulnerable to predation. Our study aims to determine how a suite of carnivores responds to the seasonal pulse of newborn ungulates using contemporaneous global positioning system (GPS) locations of four species of predators and two species of prey. We used step‐selection functions to assess whether coyotes, cougars, black bears, and bobcats encountered parturient adult female ungulates more often than expected by chance in a low‐density population of mule deer and a high‐density population of elk. We then assessed whether the carnivore species that encountered parturient prey more often than expected by chance did so by shifting their habitat use toward areas with a high probability of encountering neonates. None of the four carnivore species encountered GPS‐collared parturient mule deer more often than expected by chance. By contrast, we determined that cougar and male bear movements positioned them in the proximity of GPS‐collared parturient elk more often than expected by chance which may provide evidence of searching behavior. Although both male bears and cougars exhibited behavior consistent with active search for neonates, only male bears used elk parturition habitat in a way that dynamically tracked the phenology of the elk birth pulse suggesting that maximizing encounters with juvenile elk was a motivation when selecting resources. Our results suggest that there is high interspecific and intersexual variability in foraging strategies among large mammalian predators and their prey.

Logging, linear features, and human infrastructure shape the spatial dynamics of wolf predation on an ungulate neonate

“…Deer fawns weigh ~2.8–3.0 kg when born and can be almost wholly consumed by predators in as little as 20–60 min (unpublished data; Carstensen et al, 2009), leaving scant evidence of a kill event to be found when searching clusters of GPS locations from collared predators (Palacios & Mech, 2011). Thus, the behavioral strategies wolves and other predators use when hunting ungulate neonates have remained largely unresolved (Ruprecht et al, 2022). Researchers have shown intensive methods such as using detection dogs can locate kill sites of small prey (Petroelje et al, 2021); however, we have found that the combination of high‐frequency GPS‐fix intervals and highly trained field personnel can also successfully locate small prey kills (Gable et al, 2016, 2020, 2021; Gable & Windels, 2018), and ultimately help advance our understanding of the strategies wolves (and probably other predators) use to hunt ungulate neonates.…”

“…Predation risk for deer during the summer can be very high, with one study indicating fawns can be at risk for predation nearly daily (Mech, Morris, & Barber-Meyer, 2015). However, the exact strategies wolves and other predators use to locate hidden fawns are not well known (Ruprecht et al, 2022). Because deer fawns primarily remain motionless while bedding during the early fawning season, wolves probably use active searching strategies to seek out and locate fawns in contrast with the cursorial strategies wolves use when hunting large ungulates (i.e., out-running and outlasting prey).…”

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

“…Coyotes are one of the primary predators of neonate mule deer, with predation being a potential contributor to population dynamics, particularly within multi‐predator, multi‐prey systems where predators exhibit prey‐switching behaviours (reviewed by Forrester & Wittmer, 2013, and relevant to our study area Brunet et al., 2023). Neonate mule deer often are most vulnerable to predation during the period of early life associated with pulsed parturition (Huggler et al., 2023; Petroelje et al., 2014; Ruprecht et al., 2022) and are actively defended from predation by maternal females (Lingle, 2005; Lingle & Pellis, 2002; Wenger, 1981).…”

“…Neonate mule deer often are most vulnerable to predation during the period of early life associated with pulsed parturition (Huggler et al, 2023;Petroelje et al, 2014;Ruprecht et al, 2022) and are actively defended from predation by maternal females (Lingle, 2005;Lingle & Pellis, 2002;Wenger, 1981).…”

“…In targeting these seasonally available prey, predators (particularly smaller‐bodied predators) may employ an ephemeral shift in habitat use away from more persistent primary prey (e.g. small mammals; Huggler et al., 2023; Ruprecht et al., 2022). Proximity or overlap in habitat between prey species may facilitate use by predators and correspondingly increase risk for ungulates (Brunet et al., 2023).…”