Predator densities and white‐tailed deer fawn survival

Abstract

Predation is the dominant source of mortality for white‐tailed deer (Odocoileus virginianus) <6 months old throughout North America. Yet, few white‐tailed deer fawn survival studies have occurred in areas with 4 predator species or have considered concurrent densities of deer and predator species. We monitored survival and cause‐specific mortality from birth to 6 months for 100 neonatal fawns during 2013–2015 in the Upper Peninsula of Michigan, USA, while simultaneously estimating population densities of deer, American black bear (Ursus americanus), coyote (Canis latrans), bobcat (Lynx rufus), and gray wolf (Canis lupus). We estimated fawn predation risk in response to sex, birth mass, and date of birth. Six‐month fawn survival pooled among years was 36%, and fawn mortality risk was not related to birth mass, date of birth, or sex. Estimated mean annual deer and predator densities were 334 fawns/100 km2, 25.9 black bear/100 km2, 23.8 coyotes/100 km2, 3.8 bobcat/100 km2, and 2.8 wolves/100 km2. Despite lower estimated per‐individual kill rates, coyotes and black bears were the leading sources of fawn mortality because they had greater densities relative to bobcats and wolves. Our results indicate that the presence of more predator species in a system is not entirely additive in its effect on fawn survival. © The Wildlife Society, 2019

Interference competition between wolves and coyotes during variable prey abundance

“…Most of the study area was forested (86%) with dominant land cover types including deciduous hardwood forests, woody wetlands, and mixed forests (Appendix, Table A1 [2011 National Land Cover Data, Jin el al., 2013]). Coyote densities were about 10 times greater (23.8 individuals/100 km 2 ) than wolf densities (2.8 individuals/100 km 2 ) during 2013–2015 (Kautz et al., 2019). Densities or abundance indices for other predator and prey species in the study area include American black bears ( Ursus americanus , 25.9/100 km 2 ), bobcats ( Lynx rufus , 3.8/100 km 2 ), white‐tailed deer (571/100 km 2 [Kautz et al., 2019]), and beaver ( Castor canadensis , 0.11 colonies/km of river [J. Belant, unpublished data]).…”

“…Coyote densities were about 10 times greater (23.8 individuals/100 km 2 ) than wolf densities (2.8 individuals/100 km 2 ) during 2013–2015 (Kautz et al., 2019). Densities or abundance indices for other predator and prey species in the study area include American black bears ( Ursus americanus , 25.9/100 km 2 ), bobcats ( Lynx rufus , 3.8/100 km 2 ), white‐tailed deer (571/100 km 2 [Kautz et al., 2019]), and beaver ( Castor canadensis , 0.11 colonies/km of river [J. Belant, unpublished data]). Elevations ranged from 401 to 550 m. Monthly average May–August temperatures ranged from highs of 24.5°C during July to lows of 2.0°C during May, and average rainfall during May–August was 34.4 cm (National Oceanic and Atmospheric Administration, 2020 1981–2010 Climate Normals).…”

“…We estimated probability of occurrence by adult female and fawn deer across the landscape using a resource utilization function (RUF; Marzluff et al., 2004) to regress the occurrence distribution (OD) of individual deer on landscape covariates thought to influence their use. To estimate ODs, we used VHF relocation data from radio‐collared adult female white‐tailed deer ( n = 113) captured using Clover traps (Clover, 1956) and neonate fawn deer ( n = 100) captured using vaginal implant transmitter guided searches or opportunistically during 2013–2015 (Kautz et al., 2019, 2020). We used Brownian bridge movement models (BBMM) in package “BBMM” (Nielson et al., 2013) for program R (version 3.01, R Development Core Team, 2018) to produce a 99% OD for each deer/time period (i.e., PPP, LMP, SMP) combination (Figure 1).…”

“…We used Brownian bridge movement models (BBMM) in package “BBMM” (Nielson et al., 2013) for program R (version 3.01, R Development Core Team, 2018) to produce a 99% OD for each deer/time period (i.e., PPP, LMP, SMP) combination (Figure 1). We included adult female deer with ≥20 VHF locations or fawn deer with ≥5 VHF locations, as neonates were subject to greater predation during the first 16 weeks after birth (Kautz et al., 2019) and including only fawns with ≥20 locations would bias the average RUF toward individuals that survived. A total of 87, 89, and 94 adult female deer during PPP, LMP, and SMP, respectively, and 39 and 37 fawns during LMP and SMP, respectively, had adequate locations for analyses.…”

“…Consideration for activity and spatial segregation between these species at finer spatial and temporal scales than the home range may provide a mechanism for coexistence. In addition, diet may be important to consider as across much of eastern North America, white‐tailed deer ( Odocoileus virginianus ) are an important prey of wolves and coyotes (Arjo et al., 2002; Ballard et al., 1999), though deer age classes selected may differ between species (Arjo et al., 2002; Kautz et al., 2019; Mech & Boitani, 2003; Patterson et al., 1998). The onset of white‐tailed deer parturition provides a large influx of vulnerable prey (Petroelje et al., 2014) that exhibits immobility and hiding behavior for about 5 weeks postparturition, followed by increased mobility and social behavior (Ozoga et al., 1982).…”