Mysterious antelope deaths lead scientists to toxic yew

2010-01-14T22:20:00Z Mysterious antelope deaths lead scientists to toxic yewThe Associated Press The Associated Press
January 14, 2010 10:20 pm  • 

CHEYENNE  — It was a pretty normal morning for Todd Kittel — normal by game warden standards in that nothing is ever quite normal.

A snowstorm had come in the previous week, a mid-October bruiser, which left residents and wildlife digging out. After coming into the office, he planned to get caught up on some paperwork.

Then, the phone rang.

It was a resident on the south side of Cheyenne, calling about some antelope in his yard. When he had looked out the window, there had been two of them. Thirty minutes later, one was dead.

Kittel went to investigate the scene.

It appeared as if the animal had simply bedded down and died. There were no other clinical symptoms, no wounds or gunshots.

While Kittel didn’t know it at the time, the same thing had happened earlier that weekend. Someone had called in about another dead antelope in the area. At the time, there had been reports of a dog chasing wildlife, so the warden, Kittel’s partner, figured the animal had succumbed to exhaustion. Nothing really seemed to be awry, so he had disposed of the animal without further probing.

But now there were more dead animals.

After talking with his partner, Kittel noticed a series of similar events. The animals had been fine one minute and dead the next.

So they began looking around. Within a two-block radius, seven more animals were found.

Each scene was similar. Fresh snow was disturbed around the area, showing signs of seizures. Some had regurgitated the contents of their stomach, an indication of poison.

Kittel sent the animals in to the lab for testing, where Cynthia Tate, wildlife veterinarian for the Wyoming Game and Fish Department, examined the contents of the rumen.

The adult antelope were in good condition and the fawns were a little skinny, but not emaciated. The animals had enlarged, flabby hearts, and there was evidence of blood leaking out of the vessels into other parts of the body such as the lower abdomen and the space between muscles.

Looking at the rumen, she noticed some leaves.

“I’d never seen this in rumen before,” she said.

She showed the contents to another toxicologist who had spent many years working in Missouri. He recognized the plant immediately. It was the yew, a highly toxic plant used in landscaping.

The yew is found across the United States in many varieties; however, it is more prevalent on the West Coast, in the Southeast and the Midwest. Its range is usually confined to the lower elevations. Wyoming was always thought to be far too high for the plant.

The plant contains a cardio-toxin. While the specific process is unknown, it typically affects the heart.

“It pretty much just causes the heart to be unable to pump blood efficiently,” Tate said. “Organs get engorged with blood because the blood is not moving around. That’s about all we know.”

She said the find was surprising.

“It’s odd that these are there,” Kittel said. “This is the first known case with this toxicosis with any animal, really.”

He noted that there may have been other deaths that went unnoticed.

The plant is incredibly toxic to wildlife. He said it only takes six to 10 ounces to kill a cow or horse. Antelope have evolved to consume a lot of things, he said, but they haven’t evolved to handle this.

“Fortunately, they were able to identify what it was that killed them,” he said.

About a month later, another snowstorm came. With it came more dead antelope, this time on the other side of Cheyenne. When investigating the scenes, another yew bush was found.

“Initially, when we first had it, we assumed the things must have been newly planted,” Tate said.

But in each case, the bushes had been there for years, both homeowners being unaware of its presence. One plant was in poor condition and the other seemed to be thriving in a relatively sheltered spot.

The discovery of yet another bush, which did not have wildlife mortalities associated with it, raised some questions. If the bushes had been there for years, what was making them appealing to antelope? And why here? Why now?

“My hunch is that the weather pushed those animals in,” Kittel said.

There are a few theories on the antelope deaths, most of which point to a variety of factors. First there was the weather, driving animals into increasingly urban areas, even into parts of town itself.

Then there is the issue of urban sprawl. With the increase of rural housing and subdivisions, antelope and other wildlife are finding their former range taken up by humans. In some cases, this pushes them out, but in others they adapt, becoming less fearful.

“I’ve had people tell me that when they stepped out their front door, they almost stepped on an antelope,” Kittel said.

Add to that an increase in herd size, and you have a new ballgame. Currently all southeastern antelope herds are either at or above objectives set by the Game and Fish.

So was it a perfect storm of events? It’s hard to say. Tate said she has a feeling this is only the beginning of the story.

As botanists come up with new varieties, making plants more durable, cheap and hardy for different climate zones, we will be seeing plants that never used to grow here. And homeowners need to be wary of that, Kittel said.

“We’re already a detriment just by general pressure, but to introduce these plants ...” he said. “We need to minimize impact. We need to be responsible landowners.”

Copyright 2015 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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