field notes
tough Glove
Patricia Freeman and Cliff Lemen, bat researchers at the
University of Nebraska-Lincoln’s School of Natural Resources,
tested the puncture resistance of a variety of gloves worn when
handling bats. Using steel indenters inserted into a compression device, researchers simulated bat teeth and bite force to
test the effectiveness of leather made from cow, deer, elk, goat,
and pig. When handling bats larger than 40 grams, Freeman
and Lemen found that split-leather cowhide work gloves,
typically with a rough suede finish on both sides, are the most
puncture resistant, being tougher and less easily punctured
than the more widely-used top grain with a smooth finish.
More surprising, the researchers found that deer skin was
the best material for handling both medium and small-sized
bats, mainly because it is durable enough to withstand bites
but supple enough to allow easy, gentle handling. Goat skin,
although tough, is best used only when handling small bats.
Non-leather, “puncture-resistant” gloves proved ineffective
against bats’ thin, needle-like teeth.
Fortunately for bat researchers, deer-skin gloves are now
widely available and inexpensive. “For $12 you can get a good
pair,” Freeman says. Before buying, however, it’s wise to slip
on the gloves and feel for thin spots in the leather. One parting
tip: In addition to using safer gloves, try using a crochet hook
when handling bats. “Even with gloved hands, that little hook
can untangle the thinnest thread of mist net from the bat, better even than bare fingers do it,” Freeman says.
–As reported by Freeman and Lemen 2009
credit: cliff lemen
Resilient deer-skin gloves—most effective when handling medium and small-sized
bats—protect researcher Patricia freeman from the sharp teeth of a 16-gram
medium-sized pallid bat (Antrozous pallidus).
Building a Better duck trap
Each year the U.S. Fish and Wildlife Service and the Canadian
Wildlife Service collaborate in an effort to trap and band
thousands of migratory ducks. The cooperative program has
typically used a Benning II trap, which funnels ducks into a
single entrance and has two compartments where they remain
until banded. Charles Dieter, a professor at South Dakota
State University, wondered if there might be a trapping
method that captured more ducks without increasing mortality. One of Dieter’s graduate students found four alternative
trap designs in the literature and crafted them from wire mesh
panels. Two were oval in shape, one with a “lead” that guides
ducks to the trap; the others were cloverleaf and star shapes.
Each design had a different number of entrances and compartments where the ducks were held. Researchers learned that
the traps with more entrances also had more escapes, and
those with sharp corners increased the likelihood of injury or
death. After several tests of the designs, the researchers found
that the oval-shaped trap with a lead caught up to twice as
many ducks as the Benning II and up to five times more than
the other shapes. Importantly, all of the traps had low rates
of duck mortality, with the oval trap having among the lowest
rates—“just an added benefit” of the design, Dieter notes.
–As reported by Dieter et al. 2009
two Cannons Are Better than one
While working as a wildlife population technician with the
Idaho Department of Fish and Game, Joseph Bridges figured
out a more efficient way to scare hungry ungulates away from
farmers’ crops. When he deployed a single propane cannon
near a field, its loud explosion would chase away browsing
elk. However, the animals quickly learned that the noisy cannon did them no harm, and returned to the fields after just a
few days. To ensure a longer-lasting aversion result, Bridges
rigged two cannons near a field, intending them to explode
simultaneously. The timing accidentally got off track, which
turned out to be fortunate: Bridges found that when the cannons went off in unpredictable intervals—sometimes together,
sometimes alternately—elk took longer to become habituated
to the noises and, if they were caught before they settled in to
forage, they might simply stay away. Bridges grants that “this
is not the golden arrow to addressing depredation concerns on
crops,” and says early detection is key to increasing the likelihood of modifying animal behavior with this method. Costing
roughly $800, the two-cannon method is nevertheless a useful
and relatively cost-effective tool for managers working to deter
problem wildlife.
–Idea submitted by Joseph Bridges, now a wildlife biologist at the
University of California-Berkeley
