Educational Overview
Educational
Overview
Texas’ Desert Bighorns
SPECIES HISTORY
The
origins of our desert bighorns can be traced to the wild sheep of Eurasia.
Probably less than 100,000 years ago their ancestors migrated to North America
over the Bering Land Bridge linking Siberia with Alaska. Sheep slowly colonized
most of the western mountain ranges as far south as the northern Sierra Madre
mountains of Mexico. Glaciers and
other habitat barriers isolated populations and resulted in the variances we see
in today’s bighorns. In general terms we can divide North American wild sheep
into two species, the thinhorns in the north, and bighorns in the south, with
each of these being further divided into two distinct sub-species.
In the northernmost parts of their range the white Dall’s sheep
sub-species dominates, giving way to the Stone’s sheep variety in the Yukon
and British Columbia provinces of Canada. Rocky
Mountain Bighorns range south from the Stone’s into the southern tier of the
American states, and in the hottest, driest mountains representing the southern
reaches of their range roam the uniquely adapted Desert Bighorns.
Archeological evidence
suggests that bighorns
arrived in the southwestern United States about 10,000 years ago. Pictographs
found at the Hueco Tanks between El Paso and Van Horn indicate that native
Americans admired sheep in the mountains of West Texas as much as 2000 to 4000
years ago, and other evidence suggests that most of the arid mountain ranges in
the state held wild sheep prior to the arrival of white settlers in the mid to
late 1800’s. Side effects of that
arrival quickly sealed the fate of native bighorns in Texas with the last
sighting of a ewe in the Sierra Diablo Mountains about 1960. Market hunting
associated with the arrival of the railroad in 1881 had a detrimental effect on
sheep populations, but the final blow was most likely dealt by exposure to
diseases brought in with domestic sheep herds and the habitat restricting
effects of the fences used to contain them in the mid 1930’s.
Although
hunting bighorns was officially outlawed in Texas in 1903, and the Sierra Diablo
Wildlife Management Area was established in 1945 for the expressed purpose of
protecting Texas’ remaining wild sheep, these efforts proved unsuccessful. In
1953 the U.S. Fish and Wildlife Service, the Boone and Crockett Club, the
Wildlife Management Institute, and the Game and Fish Departments of Arizona and
Texas teamed up to try and bring bighorns back to Texas. 1957 saw desert
bighorns from Arizona released onto the Black Gap Wildlife Management Area near
Big Bend National Park, and a second transplant followed in 1959. Populations
initially grew slowly, but the double threat of predation and disease eventually
overtook the herd and most of the remaining sheep were transplanted to the
Sierra Diablo WMA in 1971. The lack of success and costs involved eroded
political support for the reintroduction efforts and resulted in the abandonment
of the program.
Fortunately this result was deemed unacceptable
by a group of determined bighorn enthusiasts. In 1980 the Texas Chapter of the
Foundation for North American Wild Sheep (FNAWS) was started, and in 1981 The
Texas Bighorn Society was formed under the leadership of Dr. James (Red) Duke,
to try and restore support for bringing bighorns back to the mountains of the
Trans Pecos region. The first project for these die-hard sheep enthusiasts was
the construction of a brood pasture facility on the Sierra Diablo Wildlife
Management Area designed by TP&W biologist Jack Kilpatrick. Constructed at a
cost of over $200,000.00, and donated to the state in 1983, this facility has
raised and released over 170 sheep into the wild from brood stock obtained from
Nevada and Utah.
In 1985 the revitalized bighorn sheep program
attracted the attention of rancher C.G. Johnson, and inspired him to donate his
23,000-acre Elephant Mountain ranch to the state to be used as a wildlife
management area devoted to the propagation of wild sheep. Disease problems at
the Sierra Diablo facility led biologists to commit the remaining brood stock to
this new area. The wisdom of this move was illustrated by the largest transplant
of bighorns in the state (45 animals, out of a herd of about 155), in December
of 2000, from Elephant Mountain to Black Gap WMA. Elephant Mountain WMA now
serves as the primary source of bighorns for restocking efforts,
although the augmentation of the program with stock from other states may still
be used to help insure genetic diversity in the future.
At one time 15 mountain ranges in the state were
populated with desert bighorns. With a little luck and the continued hard work
of volunteers, landowners, and professionals from TP&W, this can happen
again. Current census figures show that there are about 1200 wild, free roaming
desert bighorns in Texas, numbers not seen in the state since the 1800's! Enjoyment
of this success should only be tempered by the realization that the job is not
finished.
HABITAT REQUIREMENTS
The
foremost requirement for maintaining healthy populations of wild desert bighorns
is access to large areas of remote mountain habitat. The ability to move freely
over vast distances in search of water, and adequate vegetation, is essential
for large mammals in any desert habitat, and this is especially true of
bighorns. In Texas this means that travel corridors between isolated mountain
ranges must be maintained free of net wire fencing or other man made barricades
to sheep migration. The resulting mixture of the gene pool facilitated by these
migrations is also a critical component of a healthy interconnected population,
particularly here in Texas where herds probably never were, or will be extremely
large.
Suitable habitat will contain multiple water
sources in most cases, rugged escape cover, and a variety of vegetation types.
Sheep have been documented to survive without water, but given the opportunity
will drink water on a regular basis. It is possible to supplement natural water
sources with man-made water catchment systems like those constructed by the
Texas Bighorn Society. These guzzlers allow sheep to use areas of their range
that might otherwise be under utilized, and provide water for a wide variety of
wildlife as evidenced by photos taken at a water development by the TBS web cam. 
Rugged, rocky mountainside terrain provides the necessary edge when
escaping from the mountain lions, bobcats, and eagles that prey on bighorns.
Bighorns are able to eat a wide variety of vegetation, including many types of
succulent plants, and most of the grasses that grow in these mountains, but are
best served by the new growth produced behind the infrequent rains that roll
through the area.
Native species have evolved to fill differing
niches of the environment successfully, with minimal competition for the scarce
resources available here. But this balance is easily upset when exotic species
are introduced into the equation. Species such as the Aoudad from Northern
Africa have been released onto Texas mountains’ and represent serious competition for
the native bighorns. The effects of this competition are magnified at the worst
of possible times, such as during a drought when the native wildlife is already
walking the fine line of survival.
THE FUTURE
Desert bighorns are masters of survival in the
harsh and unforgiving environment that makes up their range, requiring minimal
amounts of water, and able to thrive on the scant forage available in their
chosen habitat. But that said, human beings capacity for disrupting the natural
balances that allow wildlife to survive in the desert 
mountains pose serious
threats to the future of bighorns. Land management practices, competition from
exotic species, the effect of predators on newly released populations, use of
sheep range for military training, disruption of sheep habitat by wind power
generation turbines, loss of public support for the re-introduction effort, and
the effects of climate change are issues that must be addressed if we are to
continue on the path that has brought desert bighorns back from extinction in
Texas.
Anyone concerned about bighorns needs to be
aware that their voice is crucial to maintaining political support for the sheep
program. Landowners need to understand fully the consequences of management
decisions made on their land. Conservation organizations need to work together
to maximize the effect of their efforts. Ultimately success will depend on the
continued cooperation and tireless efforts that have characterized the last two
decades being carried forward into the new century.
WHAT YOU CAN DO
As individuals we need to study and learn everything we can about issues
affecting wild bighorn sheep. Bighorns serve as an effective indicator species
in the Chihuahuan desert landscape. Healthy populations are indicative of a
habitat that will support all associated wildlife species. Knowledge of this
fact will lead us to make decisions that bode well for the entire ecosystem. We
can join, and become involved with effective conservation organizations involved
in protecting this fragile environment, such as The Texas Bighorn Society. We
must also stay informed of political issues that have the potential for
adversely affecting bighorn populations, and contact the politicians involved
and voice our concern when these issues arise. The vote is a powerful tool for
change, both for good, and bad. Financial support of programs such as TP&W’s
“Lone Star Legacy” make it possible to insure the future of wildlife
management areas like Elephant Mountain, Black Gap, and Sierra Diablo, and the
crucial role they play in bighorn management.
As landowners in desert bighorn country, your
role in the future of bighorns cannot be overstated! The lack of public land in
Texas presents a set of circumstances unique in desert bighorn re-introduction
efforts. Again,
knowledge is crucial to making informed decisions with regard to range
management. As rugged as this country is, it is also surprisingly fragile.
Overgrazing, fencing, monopolization of water resources by domestic livestock, exposure to diseases transmitted from this livestock, and the
introduction of exotic species all represent serious threats to the success of
the desert bighorn program. Windmills for power generation, and the manipulation
of groundwater for irrigation and to support growing populations in the area are
more complicated issues, and must be considered carefully with regard to their
potential impacts on wildlife.
Organizations, both public and private, may well
hold the key role in the ultimate success of 
re-introduction efforts. The
development and dissemination of accurate information crucial to making
intelligent decisions should be a primary goal of these groups. The protection
of critical habitat thru outright purchase, and the use of tools such as
conservation easements, are really only possible thru these groups, or a very
select number of well-heeled individuals. Forming effective partnerships among
involved organizations, and combining their efforts into a cohesive, ecosystem
wide based approach, will insure that we get the most bang for our buck, and
minimize conflicts or duplication of efforts.
The common threads here become quite obvious. Increasing
Our Knowledge, and Getting Involved!!! Both
are easily accomplished as individuals, and magnified exponentially as we come
together!
RECOMMENDED
RESOURCES FOR LEARNING MORE ABOUT BIGHORNS AND THEIR HABITAT:
In Print:
On the Web:
The National Bighorn Sheep Interpretive Center: www.bighorn.org
