The winter of 2010-2011 was considerably snowier than usual across much of the West, but how did that affect animals such as the bison in Yellowstone National Park?
Scientists have released the results from the park's annual summer bison population count, and it offers some answers.
According to the survey, the population this summer is estimated to be 3,700 bison. For purposes of comparison, the population was estimated at 3,900 bison last summer. The peak population estimate of 5,000 bison was recorded in the summer 2005.
There are an estimated 2,300 bison on the Northern Range this summer, with 1,400 in the Central Interior herd. The counts are based on a series of aerial surveys.
Winter mortality for the past year was estimated at 500 bison. There were 583 calves-of-the-year observed in a June aerial survey.
A park spokesperson notes, "The observed rate of population change this past year is within the natural range of expectation for wild bison. The rate at which wildlife populations increase in abundance is a reflection of the combined effects of reproduction and mortality, and is heavily influenced by age structure of the population, and environmental conditions encountered over the course of time."
"This population estimate is used to inform adaptive management strategies under the Interagency Bison Management Plan (IBMP). Specific management actions may be modified based on expected late winter population levels as corroborated by the summer population estimate."