An innovative temporary escape ramp for deer and other wildlife

Concrete-lined water conveyance canals can be a significant source of mortality for ungulates and other wildlife, which can drown or become entrapped. Various types of wildlife escape structures have been deployed in canals with limited success. From 2011 to 2018, we used camera traps to monitor mule deer (Odocoileus hemionus) use of three different temporary wildlife escape structure designs with the goal of developing an effective escape structure for fawns. We monitored three to five locations at a hydroelectric water conveyance canal, operated by Pacific Gas and Electric Company in the foothills of Central California on the Sierra National Forest, in which trapped fawns had been detected previously during the maintenance period when the canal was dry. Mule deer activity and ramp use varied by year. During the monitoring period, deer were detected in the canal in all years except 2016 and 2017. Fawns and adults used the temporary escape structures to exit the canal in four of these years and 50% of mule deer detections showed ramp use overall. No deer were detected using the escape structures until jute netting and debris were added to the surface of the escape ramps in the third monitoring year. Prior to this modification, fawns were detected trapped in the canal investigating the ramps, but not using them to exit the canal. Deer may be more likely to utilize ramps covered with materials that mimic native ground cover. Seven other wildlife species were detected entering and exiting using the ramps with a general increase in use over years. Our temporary escape ramp design for small canals, when dry, appears to be novel and may be applicable in other areas. When compared to fencing or covering the canal, it is a relatively low-cost solution to reduce animal entrapment.

De novo chromosome level assembly of the mule deer (Odocoileus hemionus) genome

The mule deer (Odocoileus hemionus) is an ungulate species that ranges from western Canada to central Mexico. Mule deer are an essential source of food for many predators, are relatively abundant, and commonly make broad migration movements. A clearer understanding of the mule deer genome can help facilitate knowledge of its population genetics, movements, and demographic history, aiding in conservation efforts. While mule deer are excellent candidates for population genomic studies because of their large population size, continuous distribution, and diversity of habitat, few genomic resources are currently available for this species. Here, we sequence and assemble the mule deer genome into a highly contiguous chromosome-length assembly for use in future research using long-read sequencing and Hi-C. We also provide a genome annotation and compare demographic histories of the mule deer and white-tail deer using PSMC. We expect this assembly to be a valuable resource in the continued study and conservation of mule deer.

Spatio-temporal analyses reveal infectious disease-driven selection in a free-ranging ungulate

Infectious diseases play an important role in wildlife population dynamics by altering individual fitness, but detecting disease-driven natural selection in free-ranging populations is difficult due to complex disease–host relationships. Chronic wasting disease (CWD) is a fatal infectious prion disease in cervids for which mutations in a single gene have been mechanistically linked to disease outcomes, providing a rare opportunity to study disease-driven selection in wildlife. In Wyoming, USA, CWD has gradually spread across mule deer ( Odocoileus hemionus ) populations, producing natural variation in disease history to evaluate selection pressure. We used spatial variation and a novel temporal comparison to investigate the relationship between CWD and a mutation at codon 225 of the mule deer prion protein gene that slows disease progression. We found that individuals with the ‘slow’ 225F allele were less likely to test positive for CWD, and the 225F allele was more common in herds exposed to CWD longer. We also found that in the past 2 decades, the 225F allele frequency increased more in herds with higher CWD prevalence. This study expanded on previous research by analysing spatio-temporal patterns of individual and herd-based disease data to present multiple lines of evidence for disease-driven selection in free-ranging wildlife.

Wolf predation patterns following recent recolonization in a multi-predator, multi-prey system

Predator-prey interactions are among the most fundamental of ecological relationships. Recolonizing gray wolf (Canis lupus Linnaeus, 1758) populations present new challenges for wildlife management in multi-prey, multi-carnivore systems. We documented diet composition and kill rates for wolves in a recently recolonized area over winter and summer seasons (2014-2015). Elk (Cervus canadensis (Erxleben, 1777)) were the primary ungulate prey (63%) located at wolf kill sites. Deer (mule deer (Odocoileus hemionus (Rafinesque, 1817)) and white-tailed deer (O. virginianus (Zimmermann, 1780)) were less prevalent than elk in wolf diets, but the amount of deer in diets (40-50%) varied by pack and season. Juvenile elk were the most prevalent class of prey in wolf diets during summer (63.3%) and winter (36.3%), with adult elk (32.5%) observed nearly as often as juveniles in winter. Kill rates varied by season, with rates 2.3 times higher in summer (x ̅= 3.5 ungulates/week/pack) than winter (x ̅ = 1.5 ungulates/week/pack), consistent with increased availability and use of neonate prey. Prey biomass acquisition did not vary by pack or season (summer = 243 kg/week/pack; winter = 182 kg/week/pack). Our study quantified predation patterns for a recolonizing wolf population, and patterns we documented were similar to other multi-prey systems in North America.