Bighorn Sheep

Ovis canadensis

Bighorn sheep are most noticeable by the massive horns for which they are named, as well as their ability to maneuver steep rocky cliffs. Weighing in at 200-300 pounds, they are one of the largest animals found in the Los Padres National Forest. They are also one of the rarest mammals in our region, with one small herd roaming deep within the Sespe Wilderness.

Image courtesy Chuck Graham; chuckgrahamphoto.com

Image courtesy Chuck Graham; chuckgrahamphoto.com

An adult ram’s set of horns often weighs over 30 pounds (which is roughly the weight of two bowling balls). Size is dependent on gender, but rams can weigh up to 300 pounds and females (called “ewes”) weigh up to 200 pounds. Bighorn sheep have a fur coat ranging in color from light brown to grey to dark brown which helps them blend in with the steep rocky slopes they inhabit. Their sharp cloven hooves are specialized to help them maneuver throughout steep cliffs and as a result, bighorn sheep can use footholds as small as two inches and climb cliff faces at speeds up to 15 mph.

Habitat

Bighorn sheep are divided into three subspecies: Rocky Mountain bighorn sheep, Sierra Nevada bighorn sheep, and Desert bighorn sheep (O. c. nelsoni), the latter of which is found in the Los Padres National Forest. All bighorn sheep inhabit areas with steep mountain slopes and cliffs so they can evade predators. The cliffs are often near open grazing areas where the sheep can graze with good visibility and flee to the safety of the cliffs or “escape habitat” when threatened. When available, bighorn sheep graze on green forbs and grasses; otherwise they can eat a variety of plants such as cacti or woody shrubs such as sagebrush. Bighorn sheep maximize nutrition extraction from food through a complex nine-step digestive process, much like that of a cow. In years of high rainfall, they can extract all the water they need from the grasses they consume. Otherwise, the trek to water can be the most dangerous part of a bighorn sheep’s life. In the absence of water-rich food sources, adult sheep can drink as little as once every three days but lambs must drink every day … making the first few years of life especially perilous.

Life Cycle

In the fall, rams battle for dominant rank and mating rights by clashing horns. These battles can sometimes be heard from over a mile away and can last over 20 hours; ram fitness and greater horn size are the largest determinants of victory. After the rutting season, pregnant ewes give birth to one (occasionally two) lamb(s). A lamb can walk after one day, but typically it will not begin to follow its mother until it is a week old. By following its mother, a lamb learns to navigate the rocky slopes of its habitat using the safest and most efficient routes. The sheep with the best routes are more likely to survive and pass them on. This way the bighorn sheep become experts at navigating their habitat over generations of time. Lambs are fully weaned by six months old, but will follow their mother for up to a year. Only one-third of lambs survive the difficulty of their first summer. Male lambs will stay in their mother’s herd for the first two to four years of their life and then join a male herd, while female lambs will stay in their mother’s herd for life. Bighorn sheep are able to breed at about two to three years old, but males are not strong competitors in the rut until about seven years old. Most bighorn sheep live to be over ten years old with a maximum lifespan of 20 years.

History of Bighorn Sheep within the Los Padres

“Even people familiar with the Sespe backcountry are surprised to learn of the mountain sheep on the slopes above the creek. Truly, their presence is something of a miracle, a testament to the rejuvenative grace of wild places. Once lost, now found, sheep in the Sespe are hope on the hoof.”

– Bradley John Monsma, The Sespe Wild

Desert bighorn sheep are native to the mountains of our region, yet went extinct around the year 1914 due to a combination of hunting and diseases transferred from domestic livestock. However, in 1985 the California Department of Fish and Game (DFG) transplanted 37 sheep from a stable population in the San Gabriel Mountains to the Sespe wilderness. Initially, the transplanted bighorn sheep had difficulties in the foreign habitat, but some survived to form a small but somewhat stable population. Yet in the early 1990s bighorn sheep within the Sespe Wilderness were becoming more and more difficult to find. In 1992, the last official survey by the DFG found only two sheep. At the same time, the San Gabriel population crashed from about 700 to only 35, which shifted conservation focus away from the Sespe bighorn sheep, causing the herd to somewhat fade into memory. Years later, starting in 1999, hikers began to report sightings of bighorn sheep within the Sespe Wilderness, and the current population is expected to be about 30 individuals (there are however no official numbers).

Image courtesy Craig R. Carey

Image courtesy Craig R. Carey

Threats

Bighorn populations have declined by 66% (90% decline in desert bighorn sheep) over the past century, which has been primarily due to unsustainable ranching, habitat loss, fire suppression, and climate change. Disease contracted from domestic livestock is historically one of the largest causes of mortality within bighorn sheep. In addition, free-roaming grazing livestock reduce the amount of available food for bighorn sheep. Habitat loss due to development is most likely the largest current threat because bighorn sheep inhabit a very specialized habitat, and any loss of it could be devastating to the remaining populations. Fires are essential to the survival of bighorn sheep because they clear away underbrush which allows for grasses to grow, exposes more escape habitat along the cliffs, and increases visibility so sheep can watch for predators. Finally, bighorn sheep populations are threatened by climate change, especially in the lower elevations, due to increasing temperatures and decreasing annual rainfall which means less food and water for the bighorn sheep.

Conservation

Conservation strategies are mostly focused upon protecting and preserving current bighorn sheep habitat. This means allowing fires to take place naturally in wild areas, restricting livestock grazing in bighorn sheep habitat, and protecting existing habitat and wild areas. Within the Sespe Wilderness, the DFG — now the California Department of Fish and Wildlife —  is hoping to reach a population size of 100 sheep, but currently there is a need for more research to understand the population size and dynamics.

Los Padres ForestWatch is proud to steward our local bighorn sheep populations and is committed to preserving and protecting our wild lands for the generations of all species to come. We’re working with state and federal biologists to develop a survey plan for bighorn sheep, in hopes that more attention and resources are devoted to this forgotten population.