Bison in The Nature Conservancy's Broken Kettle Grassland Preserve are thriving.
Scott Moats, Broken Kettle Grasslands' preserve manager, said the bison, which moved into the preserve in October 2008, have survived the winter very well.
He said there has been very little management of the herd with only a mineral supplement provided for the bison.
"We stopped breaking up ice when it became obvious that they were not using the water provided but eating snow," Moats said in a press release. "The calves from the fall look great and the cows are fat. We expect new calves in mid to late April."
Moats expects eight to 10 calves in the spring. The bison herd has 12 mature cows, with an expectation that 70-75 percent are bred.
The 28 bison have spent most of the winter on more than 150 acres.
With the opening of another gate the animals will have access to 275 more acres to graze.
The small herd will have then have access to about 500 acres, but will be less visible to the public as they are able to go farther back into the grasslands.
Opening sections of the grasslands and removing interior fencing allows the bison to be acclimated to new pastures.
The conservancy expects to reach 250 adult bison, the capacity at Broken Kettle, on 2,500 acres by October 2014.
"We expect that the herd will cover every corner of their current pasture, creating an interesting mosaic of grazing pattern, which will result in ecological benefits," Moats said. "Eventually, the herd will have access to areas that will be easily seen from the scenic overlook on Butcher Road."
The bison, which originated from the Wind Cave National Park herd, have shown no breeding with cattle as determined by current DNA testing.
The Conservancy is working closely with Texas A&M University, in College Station, Texas, to determine the best course of action to conserve that genetic integrity.
Disturbance in prairies and grasslands caused by bison grazing will mean a diversity of seeds, more light penetration for plants and a good environment for small animals like reptiles and amphibians to thrive.
The 8,000 acres at Broken Kettle Grasslands are the largest contiguous open prairie in Iowa and are part of less than .1 percent of original prairie remaining.
Broken Kettle Grasslands is in the southwestern part of Plymouth County in the northern-most portion of the Loess Hills.