Unwelcome guests at our table
ELISABETH M. BROWN
We hear a lot of bad news about declining populations of native birds
and mammals. The good news is that some native species are thriving,
but when their burgeoning populations conflict with human activities
some people do not celebrate their success.
The latest too-successful animals profiled in the media are Canada
geese and prairie dogs. Following the lead of mallard ducks, some
Canada geese have given up their migratory ways to live year round in
parks and golf courses, where they overgraze the grass, leaving in
exchange a lot of slippery droppings.
Prairie dogs in Colorado fields and schoolyards do what our local
Beechy ground squirrels do in Heisler Park: dig holes, chew
irrigation systems, rechannel runoff, and eat grass down to the dirt.
A company that literally vacuums up prairie dogs from their burrows
is thriving.
Another native animal whose recent success is not universally
celebrated is the coyote. Suburban dwellers object when their cats
and small dogs are treated as fast food by passing coyotes, who are
taking advantage of a food source in what used to be their hunting
territory.
Natural selection and evolution operate everywhere, not just in
wilderness, although we may not like the outcome. Humans create
conditions that certain animals can exploit. We give the edge to
these species, then try to get rid of them when they are successful.
I’ve watched Canada geese trying to dig through deep snow in
January to get to the dead grass beneath. It’s no wonder they choose
to stay where we keep the grass green all year long.
In the West, we replaced native grazers like buffalo and elk with
cattle and sheep, in the process converting tall-grass prairies to
short-grass ranges.
Prairie dogs, like other ground squirrels, prefer short grass. It
enables them to keep lookout for their main predators -- hawks. This
isn’t a new problem; in the old West, prairie dog holes were a
constant problem for cowpunchers’ horses.
The success of life on this planet depends on the ability of
animals and plants to evolve in response to environmental change, or
life would not have rebounded after the cataclysms in the deep past.
Humans are a direct result of climate change long ago in Africa that
shrank the forests and opened the grassy plains. Now we are now such
a dominant force on the planet that we affect most of the other
species, directly or indirectly.
We must find creative ways to manage the animals too happy with
our human environment. For now, the vacuumed prairie dogs are
delivered to endangered black-footed ferrets, their natural
predators. Ultimately, the success of the ferrets depends on the
reestablishment of a balance between prairie dogs and ferrets,
beginning by restoring the tall-grass prairie. When 100 years of
grazing ended in Laguna Coast Wilderness Park in 1993, a gradual
decline in the ground squirrel population began. Surely the same
thing could happen in Colorado.
Introduced peregrine falcons are used to control pigeons in the
steel canyons of Manhattan. Maybe we can figure out how to use those
hungry coyotes to control the ducks and geese of our urban parks.
* ELISABETH M. BROWN is a biologist and the president of Laguna
Greenbelt Inc.
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