low-cost trick to Check traps
Traps that automatically transmit a signal when occupied
may save man-hours for trap checking, but at up to $700 a
piece they may also be cost-prohibitive. Biologist Brian Dirks
and graduate student Lucas Wandrie have developed
a cost-effective solution. To capture fishers (Martes pennanti)
in Oregon’s Camp Ripley military training center, they took
working radio collars from
previous field studies and
attached them to cage traps
using zip ties. They then glued
a metal clamp (the kind used
to hang mirrors) to the transmitter to hold a small magnet,
which prevented transmission
of radio signals. Next they
connected the magnet with a
20-pound fishing line to the
trap door. When an animal
triggered the door to snap
shut, the fishing line pulled
the magnet off the transmitter, which then began to
emit a signal. This device
significantly cut the time required to check traps, reduced
human scent at traps sites (as fewer walk-ins were needed),
was quick to set up (less than 10 minutes), was inexpensive
(less than $2 per trap), and only improperly signaled without
door closure 35 times in 2,524 trap nights.
–Idea submitted by Lucas Wandrie, a graduate student at Minnesota
State University-Mankato, Brian Dirks, animal survey coordinator at
the Minnesota National Guard Camp Ripley Environmental Department, and William E. Taber, a natural resources instructor at Central
Lakes College.
credit: lucas Wandrie
An old radio collar gets new life as a
part of a signaling trap.
distinguishing Pen-reared from
Wild northern Bobwhite
Paul Castelli of the New Jersey Division of Fish and Wildlife
and Lisa Reed of Rutgers University’s Center for Vector Biology designed a stable isotope analysis to distinguish between
pen-reared and wild northern bobwhite (Colinus virginianus)
in New Jersey. “The idea came from a larger study of the
population dynamics of northern bobwhite in southern New
Jersey, where they’ve greatly declined,” Castelli says. Although
it’s standard practice to stock pen-raised northern bobwhite
into wild bobwhite habitats, Castelli and Reed noted that there
wasn’t a technique to differentiate between the two groups
when they’re recaptured or harvested. “We reasoned that birds
raised in a pen would eat different things than birds raised in
the wild,” Castelli says. Hoping that the different diets would
help them tell the two groups apart, Castelli and Reed obtained
104 feather samples from three game farms and three hunters
in the state and assayed for carbon, nitrogen, sulphur, and hydrogen isotopes. The commercially prepared diet of pen-reared
bobwhites resulted in nitrogen and carbon ratios that differed
enough to distinguish between the two groups 100 percent of
the time. In short, Castelli concludes, “The whole technique
comes down to ‘you are what you eat.’”
–Idea Submitted by Paul Castelli
easier Wolf scat sampling
For nearly two decades, researchers have extracted DNA
from wild animal scat to identify and track individuals non-invasively. This works well in freezing cold weather, which
keeps DNA intact. But in the heat of summer, genetic material tends to “go downhill pretty fast,” says Trent University’s
Linda Rutledge. This is particularly problematic in the field,
where freezers may not be available. To address this problem,
Rutledge and fellow graduate student Josh Holloway tried
something new for a study of wolves in Ontario. Rather than
take an intact piece of scat for analysis, they twirled a cotton-tipped swab along the surface of relatively fresh scat. The
reason: Wolf scats have an outer coating of mucous, which
is theoretically richer in wolf DNA and less likely to be contaminated with prey DNA than the inner feces. In the field,
Holloway swabbed wolf scats that were less than 36 hours old
and placed the samples in a lysis solution. There, the samples
could be easily stored without refrigeration and shipped
back to the lab, where Rutledge found ample wolf DNA for
her analyses. She believes that the technique “opens up huge
possibilities” for conducting non-invasive genetic studies in
less-than-ideal field conditions.
–As reported by Rutledge et al. 2009
credit: Warren Schaffer
Twirling a cotton
swab across the
mucous-coated
surface of a
wolf scat allows
researchers to
sample mainly wolf
dNA, not prey dNA,
ensuring high-quality
genetic testing.
