When discussing issues impacting bighorn sheep in the United States, three main issues dominate the conversation.
- Domestic Sheep Disease Transference
- Habitat Loss/Degradation
And those should be the three primary concerns but there is a growing threat in the Western United States.
Originally brought over by Spanish explorers in the 1500s, feral hogs have taken a foothold in 31 states and there is no question they will eventually move into all of the Lower 48.
According to an article published by the U.S. Department of Agriculture (USDA), feral hogs are a major threat to wildlife through water pollution.
“Water polluted from feral swine wallowing can be contaminated with parasites and bacteria such as giardia, salmonella, and pathogenic E. coli that could be transmitted to humans and other animals. This can happen when feral swine use an agricultural water source, such as an irrigation pond…”
They noted since hogs lack sweat glands, wallowing in mud and water is an instinctual behavior necessary for them to maintain a healthy body temperature.
“Unfortunately this behavior has cascading impacts, not only to water quality in individual streams, ponds, and wetlands, but to entire watersheds and ecosystems.”
Looking at a current distribution map, it is easy to see hogs are already established in the entirety of desert bighorn habitat in Texas and California and are also growing in numbers in New Mexico, Arizona, Colorado and Oregon.
In drought years in particular hogs will impact ponds, stock tanks, streams and guzzlers. These of course are crucial to bighorns and other wildlife.
Feral hogs can also carry pseudorabies.
According to USDA officials, pseudorabies is a disease of swine that can also affect cattle, dogs, cats, sheep, and goats.
“Pseudorabies virus (PRV) is a contagious herpesvirus that causes reproductive problems, (abortion, stillbirths), respiratory problems and occasional deaths in breeding and finishing hogs. Infected newborn pigs may exhibit central nervous system clinical signs.”
It is typically spread through direct contact but there are other ways transmission can occur.
“If present on inanimate objects, such as boots, clothing, feed, trucks, and equipment, the virus can also spread from herd to herd and farm to farm.”
Could hogs transfer PRV to domestic sheep that in turn transfer to bighorns?
And that’s a frightening prospect for animals already facing great challenges.
Another potential threat from hogs is predation.
According to officials with the Texas Parks & Wildlife Department, “wild hogs may prey on fawns, young lambs, and kid goats.”
There is no question hogs could prey on bighorn lambs, especially desert bighorn lambs in the early days of their life. I have found no concrete evidence of hog/wild sheep predation but it remains a possibility.
I will dig more into hog predation on other ungulates in another post but for now just consider what has been presented here.
No one thought 30 years ago feral hogs would now be hunted in New Jersey and more hogs would be killed by hunters in Texas than whitetails.
Could a growing population of hogs in the western United States put more stress on bighorn populations?
I believe it is a possibility, especially the water pollution and disease aspects.
I’ll let you know more as soon as I do.
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