Colorado State University Study Looks At Reproductive Inhibitors As Possible Control For Prairie Dogs
Thursday, October 16, 1997
FORT COLLINS--Does a sterile prairie dog still act like a
prairie dog?
Associate Professor William Andelt hopes to find out in a
study that begins this month on Fort Collins open space and
neighboring areas where prairie dogs make their homes.
The study, in cooperation with the U.S. Department of
Agriculturefls National Wildlife Research Center in Fort Collins,
will investigate whether surgically castrated male prairie dogs
still fill the designated role as defender of their home
territory.
If sterilization does not affect prairie dog behavior--and
pilot studies have shown that it does not--Andelt and graduate
student Aaron Schwartz believe that special baits or other
nonsurgical methods that cause sterility in prairie dogs could be
a more acceptable way of controlling the population than with
lethal means, such as poison bait or fumigation.
"We're not doing this to see if surgical castration is a
viable management tool for prairie dogs, because it would be
impractical on a large scale," Andelt said. "We want to find a
nonlethal way of controlling prairie dog populations--
particularly near urban areas of Colorado and the West, where
part of our public objects to poisoning them. That kind of
approach is in the best interest of the public and the prairie
dogs, because these animals can grow dramatically in number while
habitat diminishes."
This month, the researchers will begin marking over 200 male
and female prairie dogs. About 40-50 of the males will be trapped
and will undergo surgical castration under anesthesia, performed
by licensed veterinarians. Each prairie dog will receive an
analgesic after surgery, then released the same day to prevent
other males from taking over their territory.
During the study, Andelt and Schwartz will monitor the
castrated and uncastrated prairie dogs in the wild to see if
lower testosterone levels brought on by the surgery changes male
behavior. They also will determine if castrating yearling and
adult males increases or decreases dispersal of juvenile males
>from prairie dog towns and if castrated males have a greater or
lower tendency to disperse. It is typical for young males to
leave home and start a new one in another location. The
researchers also plan to monitor the marked females to determine
if they are bred by other unsterile males.
Prairie dogs live in colonies commonly referred to as
prairie dog towns. Small groups within the prairie dog towns,
called coteries, are generally composed of one or two adult
males, three adult females and six offspring. It's the
responsibility of adult males to fend off potential
invaders--including other male and female prairie dogs--but the
adult females and yearlings of both sexes also help.
Andelt and Schwartz do not think sterilization will have
much impact on prairie dogs, other than to possibly control their
numbers. In a pilot study this summer, five castrated male
prairie dogs showed no signs of behavioral changes by continuing
to defend their coterie territories, Andelt said. In fact, some
of the castrated prairie dogs were seen making territorial calls
the same day of surgery--an indication that surgery caused little
discomfort and that territorial tendencies were still intact.
Controlling prairie dog populations has been controversial
in Colorado and the West because of the three options used:
reducing populations by lethal means, relocating problem prairie
dogs to new habitat or excluding them with barrier fences, which
has not been completely successful.
Currently, an estimated 5 million prairie dogs occupy about
1 million acres of rangeland in Colorado. Rapid development is
taking place in areas that once were prime prairie dog habitat,
making relocation an even more remote option than it was in the
past. Few landowners want to accept relocated prairie dogs
because the animals compete with livestock for forage or
sometimes transmit plaque to pets and humans. As development
continues, encounters between humans and prairie dogs also is
becoming a public health concern. Prairie dogs, which are hosts
for fleas, occasionally carry bubonic plaque. Domestic cats can
transmit the plaque to humans via flea bites or by breath,
sometimes causing death.
However, prairie dogs are an important food source for
several species, including the endangered black-footed ferret,
badgers, coyotes and birds of prey. Their burrows serve as homes
for burrowing owls, cottontail rabbits, rattlesnakes and other
animals.
Exacerbating the problem is the prairie dogs' stealth
reproductive abilities. Each female usually gives birth to three
to five pups each spring, enabling a colony to grow by as much as
30 percent each year.
Andelt hopes that eventual use of reproductive inhibitors
will strike a balance between the need to control prairie dogs
that are a threat to public health with the need to keep healthy
prairie dog populations part of Colorado's natural environment.
Andelt said other scientists are currently working on
reproductive inhibitors that might specifically target prairie
dogs. Reproductive inhibitors are being developed for horses and
deer, but these have been delivered by injections, darts or
biodegradable bullets. A future challenge will be to develop a
practical way to administer reproductive inhibitors to prairie
dogs, such as through baits.
"We need to treat animals as humanely as possible. We think
this approach could really help sustain healthy prairie dog
populations in Colorado and still prevent them from being a
threat to public health or safety," Andelt explained.
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