It's a tough year for elk calves in Custer State Park.
A research study on elk in the park and portions of the Black Hills National Forest reached over to the Hills City area indicates that 70 percent of the 30 elk calves born this spring and fitted with radio-transmitter collars have already died.
Most were killed by mountain lions. And some of the calves had barely been born when they became meals for the predatory cats.
"There was a pulse of kills right away," said Gary Brundige, resource program manager for Custer State Park. "We had five or six of the calves killed in the first few days of life. Those were calves basically in the bedding stage."
The carnage slowed down as the elk calves grew out of that most vulnerable stage, became more mobile and could be moved away from the generally secluded bedding area and back to the company of other elk. But it did continue, and CSP wildlife specialists were able to confirm 15 lion kills out of the 30 collared.
They also presume that some of the 10 calves that slipped free of their transmitting collars - probably when they caught on barbwire fences - were killed by lions.
Figuring that in, CSP wildlife managers came up with an estimated mortality rate of 69 percent on the calves so far, with lions being the overwhelmingly dominant cause of death.
It's easy to presume that lions are the reason the elk herd in the 71,000-acre park has dwindled in recent years from more than 1,100 elk to about 225. And there's no doubt that the cats are killing elk calves and sometimes adult elk.
One of the 40 elk cows collared in the study was killed by a lion at an "elk jump," a lower area of the CSP fence that allows the animals to move in and out. The cow was presumably moving out of the park to calf last spring when the lion killed it.
But along with lions, elk in the park have struggled with lower pregnancy rates in past year. And some are believed to have migrated out into surrounding forest in a movement that could have substantial impact on the park herd.
The initial phase of the elk study showed that 10 of the 40 collared cows moved out of the park to calf last spring. The cow killed at the jump likely would have been the 11 to do that.
And they went quite a ways.
"They moved 12 to 15 miles out from where they were captured, and they stayed," Brundige said. "It's reasonable to assume that some of our reduction in numbers in the park is from movement."
It's also an open question as to whether the heavy lion predation on the elk calves is common in the park, or throughout the Black Hills. Brundige said continuing work with the collared elk next year, including following the calving process again, should provide more information on that.
Meanwhile, an expanded lion hunt in the park is aimed at reducing lion numbers there, and perhaps reducing their toll on elk and deer.
Contact Kevin Woster at 394-8413 or Kevin.firstname.lastname@example.org