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.