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A prairie dog town established in a short- or mixed-grass prairie
resembles a serene battlefield, with its mounds of dirt and burrows
pocking the grassland. But the towns are actually rich and diverse
islands of life in a wide, windswept sea of grass. In fact, one study
identified over 140 animal and plant species associated with prairie
dog towns. Bison and cattle are attracted to the many plants that
thrive on the aerated, mineral-rich soil created by the prairie dogs'
excavations. Insects and small rodents, finding travel easier on the
town's bare dirt than in the surrounding prairie, are plentiful. They
feed on the rich variety of leaves and leftover seeds and make use
of abandoned burrows. For meadowlarks and grasshopper sparrows, the
open ground is better for spotting seeds and insects. And, of course,
attracted to all of this life are the predators -- golden eagles,
hawks, foxes, coyotes, bobcats, rattlesnakes, badgers, and owls.
Because both the prairie dog and and burrowing owl are relatively
small animals living on wide and potentially dangerous open terrain,
good visibility of the surrounding prairie is essential. Prairie dogs
keep the grass trimmed, spending most of each day during the spring
and summer foraging. Traditionally bison, and now cattle, help the
prairie dogs keep the grass short around the town, giving both the
owls and the prairie dogs a better view of predators from lookouts
atop the mounds.
Burrowing owls and prairie dogs respond similarly to the approach
of a predator. Alarm calls are sounded, the prairie dogs barking and
the burrowing owls giving their cak-cak-cak-cak call. Depending on
the location and type of predator, owls and prairie dogs may scatter,
scrambling in crisscrossing beelines for burrows; or, if the danger
is less imminent, the prairie dogs begin a chorus of barking, and
the owls begin bowing and chattering. This bowing, strangely formal
and controlled given the situation, may arise from a balance between
the impulse to hide and the impulse to escape. Often the owl will
bob up and down and rather comically turn its back on the predator
as if attempting to make it simply disappear. This may be a move by
which the owl readies itself to flee. Needless to say, a prairie dog
town is a curious sight when all of this posturing and protest is
underway.
Life in a prairie dog town is thrown into full gear by the melting
of the snow in spring. In March and April the owls, which in the northern
part of their range migrate south for the winter, return, both singly
and in pairs. Each male of an already mated pair reclaims its burrow
from the year before. Unmated males find vacant burrows and set to
work cleaning them, kicking dirt backwards out the entrances with
their feet. Courtship display takes place most commonly beginning
an hour before dusk. In that delicate twilight, one can often just
barely make out the owls. The prairie dogs have gone to sleep in their
burrows. The heat of the day is subsiding. Over the western horizon,
a clear blue-white sky is tinted with faint pastels, but the rest
of the prairie is giving in to night. A high-pitched cooing begins,
higher than that of a mourning dove. Then another. And from all sides,
others. The darkened prairie is made wide again by the varying distances
of the calls, some near, some far, just as the sky is made spacious
by the gradual appearance of the stars. The male owls are singing.
At one burrow, a female is dimly visible sitting in the entrance near
her mate. She suddenly gets up, and as she does the male stops singing.
Like an uncomfortable adolescent, he stretches his wing and then his
leg, then his wing again. The female joins in, showing that this is
not simply some sort of shy shuffling but, like so much of courtship
display, perhaps a display of "certificates of health,"
proof of soundness of wing and limb. The male begins singing again,
this time stopping abruptly when the female makes a rasping sound.
He suddenly flies off, but returns shortly with a kangaroo rat in
his beak and approaches the female. She rasps even more insistently,
and he sets it down near her. She continues rasping, and the male
flies off again. This time he returns with a moth and gives that to
his mate. The female is finally satisfied after the third trip. It
is tempting to interpret this behavior as a ritualized test of capability
to rear a family. She ceases rasping, and the two begin to nip gently
at one another's bills.
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