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Part III – Invasion of the Aliens hits Bighorn Sheep

 “Watch this,” Ron Thompson was driving back to the researchers bungalow when he spotted a half dozen oryx hanging by the side of the road near a fence line. We’d stopped to watch them as they nonchalantly eyed us back . Huge, bulky, like a hefty elk with 40” scimitar-shaped horns, their beautiful and unusual black and white facial pattern reminded me of a Rorschach test. A black triangle framed their noses with mirrored white splotches on either side. Sharp black edged body markings and tan bodies, oryx have a regal exotic appearance. The animals stood and stared at the truck, just a few feet away.

“They love to race trucks. As soon as we start, they’ll run, then cut across us.” 

Oryx in Africa

My pup Hintza was in the back seat. I called to alert him to what was about to take place. As Ron gunned the truck, the oryx take off. Hintza had a happy moment watching them run, his head out the window. But the oryx don’t speed off into the horizon like the pronghorn I’m used to in Wyoming. They quickly get bored and resume standing and staring on the opposite side of the road.

We’re not in Africa where oryx are native to the Kalahari desert. This is the Chihuahuan Desert of New Mexico. Oryx, also known as Gemsbok, were brought here in the late 1960s. Frank Hibben, avid big game hunter, controversial archaeologist, professor at University of New Mexico, and chairman of the New Mexico Game and Fish Commission, had the bright idea of bringing oryx in for a big game hunting experience. To hunters, the barrenness of the Missile Range must have appeared as if they needed filling up. Researchers believed they’d simply stay within the Tularosa Basin, never growing beyond 500 to 600 animals. Mountain lions would control them, they said. But in Africa, prides of lions hunt them. Our solitary lions would rather take their chances on smaller, less formidable prey.

Ninety-three oryx were brought to the Missile Range between 1969 and 1973. Oryx barely need water, they eat anything with or without leaves, have no natural predators, and breed year round. Instead of self-limiting, the oryx thrived. The Land of Enchantment was now theirs for the overtaking. Six thousand today roam in southern New Mexico, and they need more and more room. Oryx inhabit not just the dry basins, but wander through mule deer and sheep habitat, stand on bajadas, invade washes, intrude on private lands, and comingle with bighorn sheep.

Looking from the Armendaris Ranch. Oryx inhabit these dry stretches of desert

Lindsay Smythe, San Andres Refuge Manager, tells me the Refuge allows depredation hunts from September through March. Hunters are escorted to the field, and told which one to shoot. Males have harems and the animals are difficult to sex.

Smythe is also concerned about disease transfer. “I will tell you on our bighorn sheep survey, I saw a lot of oryx up in sheep country. I started to count them, but finally gave up. We’re going to burn up too much fuel (in the helicopter) counting oryx instead of bighorn. They don’t get up into the highest steepest areas, but they do definitely interact.”

She wonders if the scabies outbreak that brought the sheep almost to extinction in the 1990s might not have been transferred from oryx. The timeline certainly fits, with precipitous drops in the bighorn population around ten years after the oryx introduction. Even so, the Refuge still has issues with other diseases common to bighorns which oryx definitely do transmit. Plus the science is still learning about the entire disease complex in bighorn sheep transmissible from other ungulates.

Even with over 1000 hunt tags issued every year, the NMGF can’t keep the oryx in check.

Nearby, on the Turner Armendaris Ranch, biologists are concerned about over browsing due to oryx. The Ranch holds oryx hunts every year, with reduced rates in the Fra Cristobals, bighorn country. Turner has one of the largest bighorn herds in New Mexico. The browse pressure from oryx compounds other thorny problems like drought and climate change.

Over in Nevada, a similar problem exists but with a more recognizable species. I called Mike Cox of Nevada Department of Wildlife to discuss bighorns there. Nevada once held the largest desert bighorn population in the West. The state’s classic basin-range topography was considered one huge metapopulation. When I began by asking about his biggest concern, he said “if you love wildlife in Nevada, the biggest problem that should be on the top of your to-do list is feral horses. We have more biomass of wild feral horses than the combined wild ungulate populations in the state of Nevada.”  I asked Cox where those horses were concentrated. Were they in bighorn country?

Historical range of bighorns in NV 1860, 1960, 2019

“They’re everywhere. They’re in the Mohave Desert, they’re in the Great Basin Desert, they’re in the sub-alpine, they’re in the alpine.”

“How many horses do you have?”

“About 60,000. Way too many cows, way too many horses. Our ecosystem is being destroyed as we speak. (Nevada) is going to be unable to move into the future if you overlay climate change.”

Even when I asked him about Nevada’s policies on mountain lion controls for bighorns, his response was telling.

“We shut a couple of bighorn herd hunts down, not because of disease, but because of lion predation and (Cox’s emphasis) feral horses.”

When I thought he was speaking solely of habitat destruction, he corrected me.

“They drink all the water. A bighorn will never go back to a water source that has a horse, ever. It’s their behavior. Because of that they get hugely impacted and die of thirst because the horses guard the water source for four months of the year.”

Cox segued into mountain lions and water sources. “When they have to go to a water source, mountain lions have such a great learned behavior and very efficient, so they can take their toll on the population. Mountain lions are not the reason that bighorns are in trouble, just the tip of the spear. There are a lot of things that contribute to bighorns not doing well.”

The overpopulation and mismanagement of wild horses and open range livestock is an enormously controversial topic. This essay isn’t about tackling or outlaying solutions for proper management, but to shine a light on how large, free-ranging, non-native ungulates imperil our ecosystems and our native wildlife across the West.

How to Age a Bighorn Sheep

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