National Wildlife Research Center (NWRC)

PROJECT GOAL: To assess the potential for CWD transmission at the interface between wild and domestic cervids, and develop methods that reduce or eliminate CWD transmission and spread.

Project Accomplishments 2008

Validation of Proximity Loggers to Study White-Tailed Deer Contact at Fine-Scales—Studies of deer behavior use techniques such as radiotelemetry, which does not have the spatial resolution needed for closely identifying contact behaviors.  NWRC scientists are determining if data-logging collars (Sitrack Tracking Solutions, Ltd., New Zealand) are reliable for collecting data at fine-scale resolution.  During 2007 and 2008, NWRC equipped 22 white-tailed deer (11 doe-fawn pairs) with the collars and conducted six 3–day trials in a 2–acre pen.  The scientists cross-referenced data from the data-loggers with visual observation data collected 1 hour before and after sunrise and sunset.  NWRC is now analyzing these data to determine whether disease transmission through direct contact between inter- and intra-related white-tailed deer increases when deer become concentrated at supplemental food sources provided by humans.  This question is critical for the regulation of deer baiting and supplemental feeding for hunting and wildlife viewing.  It is of special relevance in the Great Lakes and midwestern States where recent outbreaks of transmissible diseases, such as CWD and bTB, have occurred in captive and wild deer populations. 

Ecology of Male White-tailed Deer in the Missouri River Valley—Estimates of home range, movements, and survival are crucial to understanding white-tailed deer population dynamics.  Knowledge of these parameters can help wildlife managers establish harvest goals and design management strategies for monitoring and controlling diseases.  From 2004 to 2008, NWRC scientists evaluated the home ranges and movements of 85 radio-marked male white-tailed deer at the DeSoto National Wildlife Refuge (DNWR) in the Missouri River Valley (MRV) of eastern Nebraska and western Iowa.  The mean annual home range size was 489 hectare (ha).  Seasonal home ranges were smallest during summer (266 ha) and largest during the fall (465 ha).  Seventy-one percent of yearling males dispersed a mean distance of 14 km, with 1 ear-tagged yearling moving 121 km.   Longer-distance movements of adult males were less pronounced.  Two adult bucks migrated 3.0 and 4.5 km, and temporary excursions ranged from 1.3 to 6.0 km.  While deer dispersing from DNWR help maintain populations in outlying areas, they also create a potential risk for rapid transmission of disease throughout the MRV should they become infected.  

Resource Selection and Dispersal Direction of Sympatric Deer in Western Nebraska—Knowledge on interspecific relationships and directional movements of sympatric species such as white-tailed deer and mule deer is important, especially in areas where CWD is endemic.  The potential for contact, and thus transmission of disease, between species is related to their resource selection and spatial overlap.  In 2004, Morrill County, Nebraska, was positioned on the eastern edge of the core endemic area for CWD.  NWRC scientists initiated a 3–year study in the county to evaluate resource selection, home range size and location, movement patterns, and behaviors of mule deer and white-tailed deer relative to CWD transmission.  The scientists radio-collared 48 white-tailed and 43 mule deer and collected data from >16,600 locations from April 2004 through June 2007.  Quantifying the likelihood of interactions between white-tailed deer and mule deer (direct or indirect contact) is critical for determining interspecific transmission and spread of CWD. 

Biologists used resource selection functions to determine that 34 percent (1,500 km²) of Morrill County had a high annual probability of use by both sexes of white-tailed deer and mule deer, indicating a definite overlap in the relative use of space.  The data also showed differences in dispersal movements for white-tailed deer and mule deer.  White-tailed deer dispersed in directions parallel to river valleys, while mule deer often dispersed perpendicular to river valleys.  The differences in dispersal direction indicate that white-tailed deer infected with CWD are likely to remain within the river valley, whereas mule deer may spread CWD among river valleys. 

Evaluation of a Novel Electric Fence For Minimizing Contact of Deer With Cattle—Recent findings of bTB in cattle and free-ranging white-tailed deer in northwest Minnesota prompted NWRC to investigate alternative means for minimizing deer use of cattle pastures and stored cattle feed.  An easy-to-implement, temporary fence that can be effective when deer are food-stressed could serve to keep potentially infected deer from contacting cattle and cattle feed.  Researchers evaluated a candidate fence on 20 field sites just outside the bTB-core area in Minnesota.  The novel fence consisted of four strands of a bi-polar polytape that combined both charged and ground wires in one tape.  The polytape was coated with a peanut butter and molasses mixture to entice deer to approach and contact the fence, therefore receiving a substantial electrical shock.  The goal was to condition deer to avoid and not cross the fence.  Although NWRC has not yet fully analyzed the data, initial results show that the fence did not completely exclude deer at sites with the highest deer presence. 

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