The Wildlife Professional

Cost-saving Sentinels

A new report in Emerging Infectious Diseases (v. 14/12) could prove useful to cattle ranchers and hunters concerned that bovine tuberculosis (TB) is killing off cattle and deer. Wild deer can harbor bovine TB and pass it to neighboring livestock. When an outbreak of the disease struck Michigan’s Lower Peninsula in the 1990s, wildlife

Credit: Centers for Disease Control

managers increased the deer harvest, which
^and ^Preventionhelped greatly reduce the incidence of
bovine TB among both cattle and deer. The
disease still persists in about 2 percent of
the region’s deer, however. With infection
rates so low, conducting surveillance
becomes a difficult and expensive endeavor.
To address this problem, USDA-APHIS
researchers led by Kurt VerCauteren tested
the efficacy of using coyotes (Canis latrans),
which also carry bovine TB, as sentinels in
disease surveillance. Coyotes’ social scaven-
ger status means that several coyotes may
feed on one infected deer, and all become
infected. VerCauteren and his colleagues
sampled 175 coyotes in Michigan’s bovine
TB-endemic region and found infection
rates between 19 and 52 percent—much
higher than the prevalence rates in deer—
making it easier and more cost-efficient for
managers to monitor the waxing and waning
of bovine TB in wildlife populations.

Tracking Beavers

Researchers may have discovered a new way to use telemetry to track beavers, according to a study in Wildlife Biology (v. 14/3). With fat bodies, small heads, and an aquatic lifestyle, beavers (Castor canadensis and C. fiber) have long foiled biologists’ attempts to fit them with tracking devices that stay put for long-term studies. Aiming to rectify the

Copyright 2008 Wildlife Biology
situation, a team of researchers led by Wendy
Arjo of USDA-APHIS Wildlife Services tested
a total of six different radio transmitter
designs to see which worked best at long-
term tracking without causing undue burden
to the beavers. According to the study, the
best design involved taking what is typically
used as an ear tag, covering it in plastic, and
attaching it to a beaver’s tail. After a field trial
on 36 individual beavers in Arizona, the tail
transmitter stayed in place for an average of
344 days, tripling past records of tracking
beavers with transmitters. The authors hope
the new device will help reveal the mysteries
of beaver dispersal and movement.

Bird Strikes

Finding a dead bird next to a shiny glass window is an all-too-common experience for some office workers. But under what circumstances do building collisions become more frequent? To find out, biologists led by Augustana College’s Stephen Hager evaluated bird mortality at university buildings in northwestern and

Reprinted with permission from the
southwestern Illinois from 2002 to 2006.
Wilson Ornithological Society

Mortality at the two campuses was 24 and 55 birds per building per year, respectively, the team reports in The Wilson Journal of Ornithology (v. 120/3). Overall, the study suggests that window strikes at commercial buildings may be responsible for up to five times more bird deaths than previously believed. Though earlier studies have linked bird window collisions with bird density, another important factor was landscaping: Structures surrounded by plants that provide food and shelter to birds had more window strikes. The authors recommend taking the practical steps of installing external window screening, placing feeders away from buildings, and reducing window reflectivity by mounting them at an angle to cut down on bird deaths.

Credit: USDA Forest Service

Separating Sheep Researchers and managers have known for more than a quarter century that domestic sheep (Ovis aries) and bighorn sheep (O. canadensis) don’t mix. Massive die-offs since the 1800s have severely reduced bighorn populations in the West, and research has tied some of these deaths to respiratory infections passed from domestic to wild populations. Timothy Schommer and Melanie Woolever reviewed the current scientific understanding of disease transfer between the two populations and published their findings in a USDA Forest Service Rocky Mountain Research Station General Technical Report (209). Contact and inoculation experiments indicate that domestic sheep (and goats) often harbor pathogens that are potentially devastating to bighorn sheep. Though the precise organisms and mechanisms of transmission remain unclear, the authors recommend that managers waste no time in implementing practices that separate domestic sheep and goats from bighorn sheep in space and time to conserve bighorn populations.