As part of an effort to recover the North American plains bison population, two "genetically-pure" female bison calves were born at the Minnesota Zoo this spring--the first in 20 years.
The zoo says an estimated 30 to 60 million bison roamed North America's great plains before European settlement. The massive animals were hunted near extinction in the 1800s until a recovery effort interbred bison with cattle in the 1900s, posing a serious threat to the long-term conservation of pure wild bison.
The Minnesota Department of Natural Resources says the only evidence of the once great herds are an occasional deposit of bones, shallow depressions which were formed by wallowing buffalo and large boulders worn smooth by thousands of bison as they rubbed off their shaggy winter coats.
Now, only about 19,000 plains bison in 54 herds exist, most managed by governments and environmental organizations.
The zoo is working with the Minnesota Department of Natural Resources to conserve the threatened species.
A project started in 1961 has created a herd of nearly 100 "pure" bison at Blue Mounds State Park in southwest Minnesota. They welcomed their first calf in April.
Bison have been on display at the zoo since 1980 and currently 10 bison reside on the Northern Trail. The two new calves are planned to be released into Minnesota state parks in the fall of 2014.