Photos by Gay Miller and Stepháne Poulin

Signs of Spring
Desert Museum welcomes new arrival of baby bighorn ram

A baby bighorn ram made his debut at the Arizona-Sonora Desert Museum and has joined his parents in the Museum's bighorn sheep exhibit - just in time for Mother's Day. He was born April 25, 2003 at 6:35 a.m.

"We weren't positive that the ewe was pregnant, because we've never had one give birth so late in the Spring," said Shawnee Riplog-Peterson, the Museum's Curator of Mammalogy & Ornithology. "They typically give birth in February or March."

The baby and its mother were placed in an off-exhibit holding area for three days to make sure that the pair would bond properly and that both were doing well physically. The new baby is the offspring of a ram and ewe that were acquired by the Museum in late 2001.

In addition to the new ram, there are seven prairie dog babies and three baby hummingbirds that were born at the Museum this spring.

Bighorn Sheep Facts

What are the horns made of and how do they grow?
The horns are actually a bony outgrowth of the skull with a sheath of keratin, growing throughout the sheep's life. The ram's horns and skull may weigh 20 to 30 pounds. An adult ram's horn may measure more than 30 inches in length and reach 15 inches in circumference at the base.

What are the desert bighorns' biggest conservation challenges?
Bighorn sheep in Arizona have declined over the last century due to a variety of human-related factors including livestock diseases, habitat destruction and human disturbance. A number of the reestablishment efforts have been successful, such as the bighorn population now in the Silver Bell Mountains, west of Tucson. The natural population in the Kofa Mountains in western Arizona is one of the few stable natural populations of desert bighorn. These populations are managed today to ensure their survival.

The sheep that occupied Pusch Ridge near northwestern Tucson in the Santa Catalina Mountains have virtually vanished. Surveys of the Pusch Ridge population have been reduced to anecdotal observations.

What is the life span of a bighorn sheep?
Rams typically live nine to 12 years, while ewes usually live 10 to 14 years.

How much do bighorn sheep weigh?
An adult desert bighorn ram weighs approximately 160 pounds and a ewe weighs approximately 105 pounds.

What do bighorn sheep eat?
Although the diet of bighorn sheep varies according to the habitat and season, bighorn primarily eat grasses and browse, such as mesquite and palo verde leaves. Generally, bighorn sheep are opportunistic feeders that adapt their diet to the forage available.

What are the natural predators of bighorn sheep?
Mountain lions, bobcats, coyotes and golden eagles are predators of bighorn sheep. Eagles have been known to prey upon lambs. Predation is not a problem for healthy populations. However, when populations are suppressed by other factors, predation can be a limiting factor.

When is the breeding season for bighorn sheep?
The breeding season, or rut, generally occurs from late summer to early fall. It is during this time that rams clash heads to establish dominance and to gain access to breeding females. All bands of rams have a dominance order, and the higher- ranking (alpha) rams do most of the breeding. Most ewes give birth to one lamb per year after about a six-month (175 days) gestation period.

When is the lambing season?
Lambs can be born from January to June, with the majority of births in February and March. Prior to giving birth, adult ewes isolate themselves in secure, steep rocky areas. Newborn lambs weigh eight to 10 pounds and can walk within hours after birth. Precipitous, rough terrain helps protect lambs from predators. Lambs follow their mothers for the first year of life to learn their home range and sheep behavior.

Where might I see sheep in the wild around Tucson?
The Silver Bell Mountains has an estimated population of 50 sheep. With the establishment of the Ironwood Forest National Monument under the management of BLM, one of the expectations of this new preserve is enhanced management for these prominent creatures.

One natural population that most recently disappeared is in our own backyard, the bighorn on Pusch Ridge in the Santa Catalina Mountains. Only a few sheep from this natural relic population have been seen in the last couple of years. There are a number of hypotheses why they disappeared, but all the hypotheses are related to human-caused habitat changes and disturbances.

Who owns the Museum's desert bighorn?
A generous donation from the Desert Bighorn Sheep Society and the permission of the Arizona Game and Fish Department made possible the acquisition of these two sheep. The Museum's bighorn are on permanent loan to the Museum from the Arizona Game and Fish Department.

Learn more about Bighorn Sheep