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The numbers of the acres of prairie dogs have decreased significantly this year in Theodore Roosevelt National Park.
Resource Management staff completed mapping all 23 prairie dog towns in the South Unit and the 2 prairie dog towns in the North Unit of the park in August. With a couple of exceptions, there was a decrease in acreage for all towns. Acreage in the North Unit decreased from 136.68 to 123.86 acres, or by approximately 9.4%, and acreage in the South Unit decreased from 1,743.92 to 1,420.59 acres, or approximately 18.5%.
The park maps prairie dog towns each year, mapping the outer boundaries of the towns as indicated by active burrows. This mapping effort provides the park with a very good picture of the area in the park that is occupied by the rodents.
"Because visitors see several large prairie dog towns along the loop road in the South Unit, they often assume that there are excessive numbers of prairie dogs in the park or that the towns are continually growing," said Superintendent Valerie Naylor. "However, the towns grow and shrink with environmental conditions."
Towns grew in 2008, but shrunk in size by about the same amount in 2009. The recent expansion may have been counteracted due to abundant precipitation that prevented the prairie dogs from keeping up with clipping the rapidly growing vegetation. Town size may also have decreased due to higher predation in the areas of high vegetation. other factors that can affect prairie dogs in the park are numbers of other herbivores (heavy grazing facilitates expansion, whereas light grazing can cause reductions) and disease.
"The decrease is acreage of prairie dogs is an example of a species responding to its environment," said Naylor. "In this case it was probably due to a marked increase in precipitation, and vigorous growth of vegetation in th towns that resulted in a fairly rapid decline in prairie dog acreage."