I don't want to muck up Duck-Slayer's deer hunting post but do want to provide more information on domestic goats and respiratory disease in wild sheep.
Although evidence suggests that domestic goat strains of
Mycoplasma ovipneumoniae (MOVI) are less virulent to wild sheep than strains found in domestic sheep, it's not accurate to say there is no risk. Just like humans who contract Covid-19, the outcomes for wild sheep with MOVI are not binary (live/die). Low-grade, sub-lethal infection can persist in the adults of a herd and trigger fatal pneumonia outbreaks each summer among susceptible lambs in nursery groups, leading to low recruitment for years or decades.
A paper published a little more than a year ago looked at the genetic structure of MOVI from 594 isolates collected from domestic sheep, domestic goats, bighorn sheep, and mountain goats across the west. Researchers found that domestic goat strains of MOVI form a distinctive clade, and three strains from the domestic goat clade were identified in bighorn isolates from CO, NV, and WA, suggesting at least three spillover events. The abstract of the paper is below, and you can download the open-access paper at
this link.
The Rio Grande Gorge bighorn sheep herd is a good recent example. The Gorge herd grew from approximately 150 animals in 2012 to about 400 last year. Individuals from the herd have been tested for MOVI many times over the years and were free of the bacterium. In February 2020, 24 sheep were captured and trucked to UT to use as source stock for the Antelope Island reintroduction. All the sheep were tested and quarantined until results came back. To the biologists' dismay, 6 individuals tested positive for a domestic goat strain of MOVI and were subsequently euthanized. The remaining sheep were held in quarantine but were euthanized in March after beginning to show signs of disease.
Lamb recruitment in the Gorge is typically around 75%, which is quite good and also what has led to the outstanding growth of the population. In the summer of 2020, observers noted adult bighorns from the Gorge herd coughing, but there were no mortalities noted among collared or uncollared bighorns. However, as the summer wore on, it was clear that the lamb crop did not fare as well as in past years. An update I received just this morning indicated that recruitment in 2020 was around 30%. Hunters in the Gorge last fall reported seeing adults coughing and looking sick, yet adult mortality has still not been documented. Those who apply will notice that both ram and ewe licenses have been reduced in 2021.
Now the spillover event in the Gorge was almost certainly the result of a ram wandering and finding a domestic goat hobby flock rather than from contact with pack goats. But this event underscores the concern about the effects from even a less virulent strain of MOVI.
The risk of a spillover event from pack goats in the high country is certainly far lower than having thousands of domestic sheep grazing under the control of one herder and a couple of dogs, but it is not non-existent. As the saying goes, "stuff happens." The incident below occurred in northern Colorado last August. Unfortunately, Rambo, Tarzan, Moe, and Al were never found.
View attachment 172595
A lost goat could certainly wander around bighorn sheep country and stumble into a bighorn. Would a bighorn sheep even approach domestic goats if it encountered them? The picture below was taken in northern New Mexico (far from the Gorge) in December 2017. The nearest bighorn herd was in southern Colorado, about 50 miles away. NM Game and Fish euthanized the ram due to the risk of disease.
View attachment 172596
Even the most careful goat packer could encounter an issue in the backcountry beyond his control. Imagine climbing out of your tent in the morning and finding a young bighorn ram standing with your low lined goats. Now you know you need to report the contact, but you're 8 miles from the nearest road and don't have cell service. You have to contact the appropriate wildlife department personnel with your Inreach, explain the situation and your location, and hope they are able to respond and euthanize the bighorn before he wanders off. Good luck.
As I've told Matt in private conversation, I would like to see goat packers, federal agencies, and wild sheep advocates work together to come up with some kind of annual certification process for pack goats in wild sheep habitat, but there are many hurdles to overcome. In the meantime, we can marvel at how the federal agencies I mentioned in Matt's post have conceded the risk from pack goats and have banned their use while continuing to permit thousands and thousands of domestic sheep to graze across the landscape each year.
