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Predator Densities and White-Tailed Deer Fawn Survival
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.
Journal Article
Predation by coyotes on white-tailed deer neonates in South Carolina
Coyotes (Canis latrans) are novel predators throughout the southeastern United States and their depredation of white-tailed deer (Odocoileus virginianus) neonates may explain observed declines in some deer populations in the region, but direct evidence for such a relationship is lacking. Our objective was to quantify neonate survival rates and causes of mortality at the United States Department of Energy's Savannah River Site (SRS), South Carolina to directly evaluate degree of predation in this deer population. From 2006 to 2009, we radio-monitored 91 neonates captured with the aid of vaginal implant transmitters in pregnant adult females and opportunistic searches. Overall Kaplan—Meier survival rate to 16 weeks of age was 0.230 (95% CI = 0.155—0.328), and it varied little among years. Our best-fitting model estimated survival at 0.220 (95% CI = 0.144—0.320). This model included a quadratic time trend variable (lowest survival rate during the first week of life and increasing to near 1.000 around week 10), and Julian date of birth (survival probability declining as date of birth increased). Predation by coyotes was the most frequent cause of death among the 70 monitored neonates that died, definitively accounting for 37% of all mortalities and potentially accounting for as much as 80% when also including probable coyote predation. Predation by bobcats (Felis rufus) accounted for 7% (definitive) to 9% (including probable bobcat predation) of mortalities. The level of coyote-induced mortality we observed is consistent with the low recruitment rates exhibited in the SRS deer population since establishment of coyotes at the site. If representative of recruitment rates across South Carolina, current harvest levels appear unsustainable. This understanding is consistent with the recent declining trend in the statewide deer population. The effects of coyote predation on recruitment should be considered when setting harvest goals, regardless of whether local deer population size is currently above or below desired levels, because coyotes can substantially reduce fawn recruitment. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.
Journal Article
Deer fawns
\"In Deer Fawns, emergent readers learn about baby deer in the forest. Carefully crafted text uses high-frequency words, repetitive sentence patterns, and strong visual references to support emergent readers, ensuring reading success by making sure they aren't facing too many challenges at once.\"-- Provided by publisher.
Book
Survival of white-tailed deer fawns on Marine Corps Base Quantico
Some jurisdictions in the eastern United States have reduced harvest of white-tailed deer (Odocoileus virginianus) because of perceived declines in recruitment and population size over the last decade. Although the restoration of American black bears (Ursus americanus) and the colonization of coyotes (Canis latrans) have increased fawn predation in some areas, limited information exists on how temporally dynamic resources and weather influence fawn survival. Therefore, we evaluated fawn survival probability, cause specific mortality, and if factors such as oak (Quercus spp.) mast abundance, winter severity, precipitation, and landscape composition influenced mortality risk on Marine Corps Base Quantico in northern Virginia, USA, from 2008 to 2019. We tracked 248 fawns outfitted with very high frequency radio-collars and predation was the leading cause of mortality (n = 42; 45%). We estimated survival to 133 days and survival pooling all years (2008–2019) was 0.50 (95% CI = 0.42–0.60). Increased annual red oak (Quercus spp.) mast abundance from the previous fall reduced mortality hazard for fawns. The longevity of our study revealed a link between fawn survival and a specific maternal resource (red oak mast) only available during gestation. Our results highlight the importance of oak mast in eastern deciduous forests and, more broadly, overwinter maternal condition on white-tailed deer recruitment.
Journal Article
Farrah the shy fawn
It is the beginning of summer and Farrah the fawn wants to look beautiful for the petal parade, but when she tries the leaves of a supposedly magical plant they just seem to make her sick, and the superfairies have to rescue her.
Book
Landscape-Level Patterns in Fawn Survival Across North America
A landscape-level meta-analysis approach to examining early survival of ungulates may elucidate patterns in survival not evident from individual studies. Despite numerous efforts, the relationship between fawn survival and habitat characteristics remains unclear and there has been no attempt to examine trends in survival across landscape types with adequate replication. In 2015–2016, we radiomarked 98 white-tailed deer (Odocoileus virginianus) fawns in 2 study areas in Pennsylvania. By using a meta-analysis approach, we compared fawn survival estimates from across North America using published data from 29 populations in 16 states to identify patterns in survival and cause-specific mortality related to landscape characteristics, predator communities, and deer population density. We modeled fawn survival relative to percentage of agricultural land cover and deer density. Estimated average survival to 3–6 months of age was 0.414 ± 0.062 (SE) in contiguous forest landscapes (no agriculture) and for every 10% increase in land area in agriculture, fawn survival increased 0.049 ± 0.014. We classified cause-specific mortality as human-caused, natural (excluding predation), and predation according to agriculturally dominated, forested, and mixed (i.e., both agricultural and forest cover) landscapes. Predation was the greatest source of mortality in all landscapes. Landscapes with mixed forest and agricultural cover had greater proportions and rates of human-caused mortalities, and lower proportions and rates of mortality due to predators, when compared to forested landscapes. Proportion and rate of natural deaths did not differ among landscapes. We failed to detect any relationship between fawn survival and deer density. The results highlight the need to consider multiple spatial scales when accounting for factors that influence fawn survival. Furthermore, variation in mortality sources and rates among landscapes indicate the potential for altered landscape mosaics to influence fawn survival rates. Wildlife managers can use the meta-analysis to identify factors that will facilitate comparisons of results among studies and advance a better understanding of patterns in fawn survival.
Journal Article
Vaginal Implant Transmitters as a Tool for Pronghorn Fawn Capture
During a pronghorn (Antilocapra americana) translocation study in New Mexico, USA, in 2014, we outfitted 26 pregnant female pronghorn with vaginal implant transmitters (VITs) to better understand cause-specific fawn mortality. All VITs were equipped with both temperature and photo (i.e., light) sensors. Partial expulsions were detected from VITs in April 2014, at least 2 weeks prior to fawn observations. In these instances, VITs were exposed to ambient daylight activating the photo sensor, which was “reset” daily after sunset. These false signals likely compromised both battery life as well as detection of actual fawn births as a result of time spent tracking false expulsions rather than focusing efforts on fawn capture. We tracked VITs of 19 females (n = 16 confirmed expelled). Expelled VITs assisted with fawn captures (n = 12) from 8 females. We were unable to capture fawns from some females with VITs because fawns were too old to capture or VIT signal failure limited our ability to correctly determine whether a birth occurred. Failure here is defined as a signal we were unable to hear due either to battery failure or geographic location of the VIT post-expulsion. We also opportunistically captured fawns, either by monitoring and observing females outfitted with very-high-frequency (VHF) collars or using long-range observations of unmarked females. Opportunistic captures resulted in fawn captures (n = 4) from 3 females with only VHF collars, and 13 fawns from 13 unmarked females. Fawn capture success from females whose VIT expelled was greater because fawns were smaller and less likely to flee. To minimize false expulsion signals in VITs, we recommend 1) modification of VIT wings to maintain position inside the vaginal canal until parturition, and 2) change VIT design to specifically fit pronghorn (i.e., design VITs using specific pronghorn vaginal canal measurement to ensure better VIT fit) to prevent premature partial or total expulsion.
Journal Article
Landscape Heterogeneity Reduces Coyote Predation on White-Tailed Deer Fawns
Coyote (Canis latrans) predation on white-tailed deer (Odocoileus virginianus) fawns in southeastern North America has led to deer population declines in some areas. Research or management efforts initiated in response to coyote predation on fawns have primarily focused on implementation of reduced antlerless deer harvest or coyote control to mitigate population declines. Vegetation characteristics may influence coyote hunting efficiency, but the potential influence of land cover at large scales in the southeastern United States is underexplored. We investigated whether mortality risk was affected by landscape characteristics within fawn home ranges for a sample of 165 fawns on the United States Department of Energy’s Savannah River Site (SRS), South Carolina, 2007–2012. We monitored fawns every 8 hours to ≥4 weeks of age and 1–3 times daily to 12 weeks of age. We included only surviving or coyote-predated fawns in the dataset. The most supported model describing hazard ratios included the length of edge (i.e., area where 2 land cover types joined) in fawn home ranges. Probability of coyote predation increased 1.26 times for each 968-m decrease in edge within a fawn’s simulated home range (29.1-ha circular buffer) under this model. Further, fawns with the least edge in their home ranges were >2 times more likely to be depredated by a coyote than fawns with the greatest edge availability. Support for other models was relatively low, but informative variables (e.g., mean patch fractal dimension, Shannon’s diversity index, mean forest patch size) supported a general trend that as fawn home ranges became more homogeneous and contained larger patches with less edge and fewer cover types, predation risk increased. These findings are consistent with similar work in the midwestern United States, despite landscape differences between regions. The combined weight of evidence suggests maintenance of a heterogeneous landscape consisting of relatively small dispersed patches may reduce fawn losses to coyotes. This information may also be used to identify areas susceptible to greater fawn predation rates across large spatial scales. However, the relatively long forestry rotation lengths and large scale of consistent forest management on the SRS are uncommon in the southeastern United States and the mechanism for the pattern we observed is unclear. Therefore, our results may not be applicable to sites with different forest management practices.
Journal Article