Bighorn sheep seen along the Colorado River

Deep in the heart of the desert, in one of the hottest, driest and most inhospitable places in Arizona, lives a majestic desert dweller: the bighorn sheep.

A group of 31 people boarded boats at Willow Beach, 10 miles south of Hoover Dam, and braved the heat to try to get a look at these incredibly adaptable creatures along the shores of the Colorado River Saturday – and they were not disappointed.

Host David Boyd, Arizona Game and Fish Department information and education program manager at the Kingman office, told the group assembled for a workshop the evening before the excursion that he could not guarantee a sighting of the shy, elusive bighorn.

But he need not have worried about anyone being disappointed.

Sightings of rams, and ewes with their lambs along the Colorado River from Willow Beach to Hoover Dam, were plentiful against the splendor of the river and its surroundings.

Nancy Brosius, who attended the field trip with her husband, Jim, said she enjoyed the trip.

"My husband and are park docents.

Now when people ask us a question about desert bighorn sheep, we can give them an answer," she said.

Those who attended were also required to attend a two-hour workshop the evening before to learn about the sheep.

"There are not many places to see bighorn sheep.

Mohave County has one of the highest populations of bighorn sheep in the world," Boyd said.

Desert bighorn sheep can vary in size with the male weighing in at about 250 pounds and the female at about 140.

The skull and horns of a ram can weigh up to 40 pounds.

Both the male and female have horns - not antlers - which consist of a bony core with a sheath covering and the impressive horns can show growth rings similar to tree rings.

Rams use the horns to engage in head-butting and posturing, sexual traits related to establishing dominance among rams and to attract ewes for breeding.

The ram develops a spongy tissue that becomes inflated during prolonged bouts of head-butting that acts to absorb some of the shock of the head-butting blows.

The blows have been known to cause concussions, however.

At the workshop Boyd told the group about a large ram found dead in the desert.

A necropsy (an autopsy done on animals) revealed that the animal had died of a concussion.

Boyd explained that when bighorn go into their breeding season, which is just beginning, rams tend to engage in more aggressive head-butting behavior.

Special adaptations have helped desert bighorns to not only survive their harsh desert habitat, but to thrive.

Physical adaptations include a specialized hoof that works like a suction cup, allowing the bighorn to climb steep, rocky terrain.

The outer edge of the hoof is hard and sharp, while the inner part is soft and protruding for gripping rock surfaces.

Their agility helps them to navigate their steep terrain to evade predators, which include mountain lions, bobcats, coyote and even eagles.

They can also run more than 30 mph.

Another advantage bighorns have is large eyes positioned on the sides of their heads to help them spot predators sneaking up from behind, and their exceptional eyesight - comparable to eight power binoculars, Boyd told the group at the workshop.

But the desert bighorn's specialized adaptations to high temperatures and low water availability, allowing it to withstand high body temperatures of up to 107 degrees, is what makes it able to survive the desert temperatures.

The bighorn also have a high concentration of blood vessels in its underside, which allows the animal to quickly lose excess body heat, Boyd said.

Bighorns are able to go for long periods of time without water, losing up to 30 percent of their body weight in water (more than a camel) and then replenishing this loss in one drink of 4.5 gallons of water in fewer than two minutes.

However, if water is available, they normally drink more often, Boyd said.

In Arizona bighorn sheep are found in the Mohave and Sonoran deserts and are primarily browsers, feeding on a wide variety of leaves, twigs, flowers, grasses and cacti.

They tend to be more active in the hot summer than any other time of the year because the summer months are the only months that they breed, Boyd said.

During breeding season rams sometimes become aggressive toward other rams in an attempt to compete for ewes.

Those on the boat trip witnessed a display of this aggressive behavior when two rams in a group of about eight bighorns began to butt heads, but there were no injuries.

Started 10 years ago as teacher workshops, Boyd said the public soon became interested in learning about the unique bighorn sheep.

"This is the start of the breeding season for bighorn sheep and the group can see the rams with the ewes drinking water," he said.

"When in a boat, the sheep allow people to get a little closer than they would on land, because they know they have an escape route."

In 1957 the Arizona Game and Fish Department began a program to reintroduce bighorn to parts of their historic range, where they had become obsolete.

The workshop and field trip is sponsored in part by the Heritage Fund and the Arizona Desert Bighorn Sheep Society.