A biologist uses an antenna to locate a desert bighorn fitted with a radio telemetry collar.
August 29, 2013
Two weeks ago, sick bighorn sheep were discovered for the first time in the Marble Mountains, about 30 miles south of Old Dad Mountain where the original outbreak of pneumonia was discovered. Tests confirm that bighorn in the Marble Mountains have the same strain of pneumonia as the Old Dad Herd. The Marble Mountains are located just south of Interstate 40 on the east side of Kelbaker Road, on lands managed by the Bureau of Land Management.
November 14, 2013
During the week of November 3rd, an interagency team of scientists worked with a contract animal capture expert to place Global Positioning System (GPS) and radio-telemetry monitoring collars on bighorn sheep in twelve mountain ranges in the Mojave Desert. The investigation was an interagency collaboration directed by the National Park Service and California Department of Fish and Wildlife. The team placed collars on 72 desert bighorn sheep, and biological samples were collected from each animal.
The goal of the investigation is to help scientists better understand the distribution of the disease, monitor its spread, and learn about demographic effects of the disease on bighorn herds. This information will allow both agencies to make well informed management decisions regarding bighorn sheep in the future.
As part of this investigation, the team had intended to capture, euthanize, and necropsy animals displaying clinical signs of the disease. Surprisingly, few animals were encountered showing any signs of the disease.
Using visual assessments, scientists were unable to detect any spread of the disease beyond the known areas of Old Dad Peak and Marble Mountains. However, laboratory analysis of biological samples may provide more definitive information. (See April 2, 2014 update below)
The only mountain where carcasses were found was the Old Dad Peak area. Most of these were old carcasses from earlier in the year. However, the overall encounter rate and total number observed during the operation were approximately one-third to one-half of expectations based on past experience. This could be in part due to other factors unrelated to disease, such as movement to areas of better forage or dispersal over a wider area that would make the animals more difficult to detect.
Data collected over the coming months from the bighorn that were collared during this operation will provide essential information about the extent and effects of this disease outbreak and will better inform management decisions.
April 2, 2014
Laboratory analysis of biological samples taken from bighorn during the November 2013 collaring effort demonstrated that the pneumonia outbreak is present across the research area. Impacted herds now include those in mountain ranges within Mojave National Preserve; the South Bristol, Marble, and Clipper Mountains south of I-40; and the Spring Mountains in Nevada. A different strain of pneumonia has been detected in the River Mountains near Boulder City, Nevada, and into Arizona. Plans for stepping up observations of herds within Death Valley National Park are underway.
Of the 72 sheep collared in November 2013, only six have died, and scientists report that they observed fewer sick and dying sheep in the mountain ranges south of I-40, even though laboratory analysis show this herd is carrying the bacteria that cause this disease. Scientists continue to monitor collared sheep, with a focus on lambing and disease transmission to young animals.
The next major helicopter survey of the entire region is planned for fall 2014.