A bighorn sheep grazes.
CO082906_D001 A bighorn sheep grazes. © Tim Sullivan

Stories in North Dakota

North Dakota Nature Notes

November brings out one of the best spectacles of nature in North Dakota – bighorn sheep battles.

In November, bighorn sheep undertake their fall breeding behavior called the rut. Most hoofed mammals are “in rut” earlier; pronghorn are among the first, starting their rut in September. Bighorn sheep are among the last to breed and the competition between rams for ewes can make for spectacular wildlife watching.

The rut is when antlers and horns are put to use – it is this headgear that can decide who gets to mate. Antlers are shed after the rut and grow back before the next breeding season. Horns, however, are not shed. They grow incrementally year-by-year and older bighorn rams can have an impressive pair. One record-setting ram had horns each of which were more than 45 inches long and were greater than 16 inches in circumference at their base. Ewes have horns too, but they are slender, and so short they do not extend for more than a half-circle. Some rams have horns so massive that their forward curl may actually reduce the ram’s side vision.

Rams and ewes keep apart until fall: the rams in bachelor herds and the ewes with their lambs in larger nursery herds. By October, these two groups begin to intermingle and soon the rams are competing for mates. Smaller rams give way to the older males but more evenly matched males do not yield without a fight. Their contests are most frequent in November. Battling males gradually approach each other until 30 or 40 feet apart when they simultaneously rear up on their hind legs then lunge forward to collide head-on. The loud crack of their smacking horns can be heard a mile away on a calm day. The dazed rams pause, recover, then repeat the charge. The contest can continue for hours, ending only when one of the rams yields.

Bighorn sheep were admired by early explorers to the Dakotas – in 1843, Audubon described the sheep he saw near the Missouri River and the subspecies native to the region bears his name. Sadly, subsequent explorers and settlers admired the sheep too well: by 1905, Audubon’s bighorn sheep was extinct in North Dakota. The subspecies is gone forever, but bighorn sheep from other parts of North America have been reintroduced into their range. Today, the population in the state is estimated at a few hundred animals, and one of the best places to see them is on the Moody Plateau, along the Little Missouri National Grassland automobile tour that begins in Medora, not far from Theodore Roosevelt National Park.