Disease could devastate region’s endangered herds

  • November 11, 2013 at 10:39 pm #955

    By J. Harry Jones


    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
    State Park.

    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,”
    Jorgensen said.

    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

    • This topic was modified 9 years, 7 months ago by admin.

The forum ‘Strange Animal Deaths’ is closed to new topics and replies.