field trip to
This field trip was attended by Lee McDowell and Valerie
Janis.† Conservation biology instructor
Steve Platt and Mammalogy class instructor Jim Taulman were also present.†
Wildlife Biologist Dan Roddy explains aspects of ungulate ecology to Lee, Steve, and Valerie.
Marie described the three main vegetation issues currently being addressed through †research and monitoring at the park:† 1) protection of hardwood species that serve as important nutritional browse for ungulates, 2) control of noxious and introduced weeds that tend to outcompete native grasses, and 3) enhancing the vigor of native grasses in order to provide abundant resources for the grazing mammals here.
Of the 20% of the plants in the park that are exotic, many of those are troublesome or noxious weeds.† Four of the eight thistle species are non native plants.† Canada thistle is a particularly problematic species that park biologists have had some success controlling with the stem gall fly, a host specific insect parasite.† Leafy spurge is treated with a specific flea beetle that attacks it and consumes leaf tissue.† Other non native weeds, such as spotted knapweed are attacked by the stem mining weevil and other biological insect control parasites.
Botanist Marie Curtain describes a project in which some 45 acres have been fenced to protect an aspen grove that was in danger of being overbrowsed and eliminated.
The capacity of the park to support its ungulate population (the bison, pronghorn antelope, mule deer, white-tailed deer, elk) as well as other important herbivores like the black-tailed prairie dog, is determined by sampling grasses during summer and estimating total grassland forage availability.†
Woody browse important to ungulates at the park.
About 31 million pounds of foods are provided by the grasses in the park during the growing season, but hot all of that is available to the wildlife there.† Ecologists know that it is important to allow about half of the grasses to remain ungrazed in order to maintain adequate ground cover and allow the grass species to reproduce and sustain the health of the grassland community.† And about half of the forage available for grazers may be lost to various environmental factors, such as insect infestation, damage by trampling, or hail storms or other weather.†
A summer hail storm on the prairie will cause damage to grasses and even may harm birds and other wildlife.
So only about 25% of the grassland forage produced each summer is available to be eaten by the mammal populations in the park.† This quantity of food amounts to about 10,000 animal use months (AUM), a unit that allows evaluation of the ability of the parkís grassland to feed the animals living there.
Research ongoing at the park will determine the number of AUMs of forage needed by individual animals of each of the grazing species in the park. †That will allow accurate estimation of the carrying capacity of the park for each species.† It has already been determined that a bison requires about 1.2 AUM of forage and there are currently in the range of 450-500 bison in the park.† If biologists decide that the park has more bison than it can support, individuals will be sold to tribes or individuals with other private herds.†
Bison cow and calf at the park.
In addition, the bison herd is currently in excellent health.† The last known case of Brucellosis was found in 1984 and the herd has been disease free since then.
Dan and Marie told us about the situation with chronic
wasting disease (CWD) in the deer and elk herds in and around the park.† Apparently the disease was first detected in
an elk population brought to the Casey ranch adjacent to the park, where the
first elk with CWD were detected in the late 1990s.† All 250 elk in that herd were killed and
their carcasses burned and buried.† Since
then about 3 additional wild elk have been found with CWD.† Research conducted in the park on deer by
Kristin Schuller, a graduate student at
The elk population in the park has grown to about twice the size that is desired.† Since CWD has been found to occur in local elk, even though the incidence is low, elk cannot be live shipped to other areas.† The best strategy for dealing with this large population is currently being studied and a management plan will be created with professional and public input.
Looking like part of the grassland, this porcupine travels cross country to another forest patch.
We also discussed the role of prairie dogs at the park and in the shortgrass prairie ecosystem.† While prairie dogs clearly clip and eat much of the grass around their burrows, this clipping also invigorates grasses to grow and produce a more nutritious shoot.† The same effect is seen in suburban lawns that are mown regularly.†
Dan discusses the role of prairie dogs in the grassland ecosystem with Valerie, Steve, and Lee.† Valerie is planning on doing a study of prairie dog ecology and habitat use on the Pine Ridge reservation for her masterís thesis.
Prairie dogs provide a wide range of ecological benefits to the grassland and are an essential component of the shortgrass prairie ecosystem.† Their burrows provide needed refuges and nesting habitat for a diverse community of species, such as burrowing owls, snakes, amphibians, insects, and others.† In addition, prairie dogs are an important food resource for such predators as raptors, badgers, coyotes and foxes, black-footed ferrets, and snakes.
Prairie dogs provide valuable ecological benefits to the shortgrass prairie community.
Our visit with biologists Dan Roddy and Marie Curtin was
very enjoyable and instructional.† This
park is providing an example of how to properly manage our native wild mammals
being released into the