Nevada Department of Wildlife (NDOW) biologists continue to find bighorn sheep that have died due to complications brought on by pneumonia in the East Humboldt Range and in the Ruby Mountains.
"We have found 74 dead bighorn sheep in the East Humboldt's (hunt unit 101) and 28 in the Ruby Mountains (hunt unit 102) for a total of 102 sheep over the last 4 months," says Caleb McAdoo, NDOW big game biologist. "Unfortunately, this disease event isn't showing any signs of abating."
While the numbers make it appear that the East Humboldt herd is doing much worse than the Ruby Mountain herd, McAdoo explains that the mortality detection rate on the winter range in hunt unit 102 is lower due to terrain.
"It is very possible the die-off in unit 102 is just as severe as the event in the East Humboldt's," cautions McAdoo. "We are concerned that as many as 80% of each herd may succumb before the winter is over."
NDOW biologists are also concerned about the survival of any lambs born this spring. In past disease events, young lambs appear to have been exposed to pneumonia that is still present in the adults and then die within the first couple of months of life because they don't have any natural defense to the disease.
Because of issues like this and other concerns, NDOW biologists and veterinarians have put together a plan to monitor and study the sheep for the next few years. They have tagged and placed radio collars on a number of sheep as well as administering a broad spectrum antibiotic to some of the animals.
Biological samples have been taken from dead and healthy sheep for comparison to see if minerals, forage quality or even genetics play a role in determining which animals may live and which may die. NDOW personnel will follow the marked animals trying to see if there is anything that separates those sheep that survive from those that didn't.
Soil and forage samples are also being taken to explore what affect forage quality and trace minerals in the forage may have on both diseased and healthy animals.
"Unfortunately, there is no known cure, or treatment for pneumonia in bighorn sheep," said McAdoo, "but we are going to use the data collected from this disease event to assist in future outbreaks."
To avoid putting more stress on the animals than is necessary, work is being done from the ground as much as possible, as helicopters cause the animals to try to evade and escape using up precious energy. The full extent of the die-off may not be known for months depending on the success of follow-up surveys from the ground or from the air once the sheep have had time to recover from the winter.
So far only one Rocky Mountain goat has been found that has died from pneumonia. Preliminary survey data indicates that the goats have not been as negatively impacted by the disease.
With the coming of warmer weather and snowmelt, the public is anxious to get out of the house. But McAdoo is asking the public to please give the bighorn sheep space and avoid the areas they are in so as not to stress them.
"We are still within a critical time for these animals," says McAdoo, "as the weather warms and forage starts to green up, they have a chance to build some strength. Any extra energy demands placed on the sheep may decrease their chances of survival."
The Nevada Department of Wildlife (NDOW) protects, restores and manages fish and wildlife, and promotes fishing, hunting, and boating safety. NDOW's wildlife and habitat conservation efforts are primarily funded by sportsmen's license and conservation fees and a federal surcharge on hunting and fishing gear. Support wildlife and habitat conservation in Nevada by purchasing a hunting, fishing, or combination license. For more information, visit www.ndow.org