November 11, 2013 at 10:39 pm #955MikeKeymaster
By J. Harry Jones
UNION-TRIBUNE STAFF WRITER
August 27, 2005
A recent surge in deaths among an endangered bighorn species in
Southern California has biologists and environmentalists worried that
an epidemic could be killing off the animals.
Two weeks ago, seven Peninsular bighorn sheep were found dead from
pneumonia in the San Jacinto and Santa Rosa mountains near Palm
EDUARDO CONTRERAS / Union-Tribune
About 700 Peninsular bighorn, such as these in Anza-Borrego Desert
State Park, live in the mountains from I-8 to Palm Springs.
Yesterday, a helicopter survey of herds in the same area determined
that at least 20 of a group of 75 sheep were missing and believed
dead, said Jim DeForge, the director of the Bighorn Institute in Palm
Wildlife officials fear that the pneumonia might be caused by a
virus, which could spread by nose-to-nose contact. They say it is
unclear how many animals might be affected but that several have
exhibited troubling symptoms.
To determine whether a virus is to blame, officials have proposed
capturing one or two sick bighorn for testing.
But because reintroducing those bighorn into the wild or putting them
in a zoo further risks infecting other animals, officials say they
would have to kill the animals after the tests.
The state listed the Peninsular bighorn sheep as an endangered
species 34 years ago, nd the animals’ numbers continued to decline,
according to the Palm Desert-based Bighorn Institute’s Web site. A
decade ago, about 300 were left.
The animals gained federal protection in 1998, when the U.S. Fish &
Wildlife Service determined they were in danger of extinction from
factors including disease, parasites, mountain lions, automobiles,
and loss of habitat from development such as golf courses.
About 700 Peninsular bighorn live in nine groups in the mountains
from Interstate 8 north to Palm Springs. More than half of those live
in San Diego County, the majority in Anza-Borrego Desert State Park.
“For the past few years, things have been going in the right
direction,” said Walter Boyce, director of the University of
California Davis Wildlife Health Center. “This is the first
significant blip in the recovery effort in the past few years. We’re
concerned this is the beginning of an epidemic.”
Desert bighorn sheep forage for various grasses and shrubs. Adult
rams weigh 150 to 200 pounds and have large spiral horns that grow
throughout their lives. They can be as old as 12. Females, or ewes,
have slender, straighter horns, weigh 100 to 125 pounds and can live
to be 14.
Animals in large herds of various bighorn species across the western
United States have historically died from pneumonia. But experts say
an epidemic among the Peninsular bighorn would be devastating because
the herds are so small.
Last year, DeForge said, wildlife officials counted 15 lambs near the
northern boundaries of the Peninsular bighorn’s habitat, but
yesterday they could account for only four or five year-old sheep.
“We’re the only ones doing intensive field work (in that area) right
now,” DeForge said. “How widespread is this? Is it throughout all the
ranges? We just don’t know.”
Boyce said an aerial survey Thursday over all of the bighorn’s
habitat was more encouraging. It showed that 48 of 50 animals with
radio tracking collars on their necks were alive.
Until recently, mountain lions were the primary cause of death among
the Peninsular herd, which had been relatively disease-free.
Officials say there are two main theories about how the sickness is
spreading. If caused by bacteria, the disease probably is transmitted
by biting gnats or black flies, whose numbers have increased
significantly because of more than 2½ inches of summer rain in the
desert, said Mark Jorgensen, superintendent of Anza-Borrego Desert
If that is the case, Boyce said, little can be done to protect the
But if the cause is viral, the goal would be to keep the nine groups
of sheep separated. Although the herds tend not to mix, some of the
larger rams often roam among nearby groups.
Jorgensen said that if one or two of the groups in the mountains near
Palm Springs are found to be infected with a virus, officials could
take unprecendented steps to stop rams from mingling with other
For example, the territory where four of the northern groups roam is
bounded by roads, he said, so “theoretically, you could erect some
temporary fencing along a paved highway.”
“It’s an extreme move and it may never happen, but it is an idea,”
But experts must first find out what is killing the bighorn.
Boyce said the next step is to find a sick sheep and to take saliva
and blood samples before it dies. Those samples should provide the
biological information needed to determine the cause of the disease.
But getting the samples could prove difficult, DeForge said
yesterday, because they must be taken from live sheep.
“One of the problems is they appear to be fine right up until they
die,” he said.
If scientists decide to try to capture one or more sick bighorn, the
animals will be taken to a lab in San Bernardino for testing. DeForge
said biologists also might try to take blood samples from bighorn
from all over their range.
Concerns about the sheep in San Diego County were first raised last
An annual watering hole population survey in July in the Anza Borrego
park found a low number of lambs, Jorgensen said. A number of bighorn
also were observed to be coughing, indicating respiratory problems.
In addition to the Peninsular bighorn in Southern California, a
separate herd of 2,000 to 2,500 sheep live in the mountains of Baja
California. Jorgensen said there have been no sightings of bighorn in
the United States south of Interstate 8 for 15 years, making it
unlikely that a virus, if it exists, could spread to the Mexico
J. Harry Jones
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