Evergreen yews can poison livestock, pets
Stressed for food this winter, a herd of pronghorn antelope ventured into some Idaho homes to browse the landscaping. They found tasty evergreens sheared into nice conical forms. All the antelope died where they fed.
Fish and game experts arrived to discover what had caused it. They examined the animal’s mouths and digestive systems to see what they had been eating. In the esophagus they found sticks and leaves of that nearby evergreen. Identified as Japanese yew (Taxus cuspidata), it was found throughout the digestive tract by the time death occurred, proving no immediate ill effects for discouragement.
This sparked recollected lore in an old tree book describing how cattle in England were found dead after escaping pasture to feed on 1,000-yearold yews (Taxus baccata) at a nearby churchyard. Churchyard yews are the few ancients left of more extensive stands gradually depleted over millennia to create grazing land free of poison risk. Both English yew and Japanese yew are both members of the same toxic genus that also resulted in the cancer drug Taxol.
The incident with the antelope and another with eight dead elk a few weeks earlier demonstrates how animals both wild and domestic can change their feeding habits when under stress, be it weather, boredom or inadequate feed. When they come upon ornamental plants, they will all sample and continue, or if unpalatable, they move on.
The bigger problem is that Taxus in gardens can kill your horses, cows, chickens and goats, too. Most folks can’t identify plants in their yard so you probably have no idea if Taxus species are there. Bring pets and kids and livestock into contact with yews where it’s certain they’ll sample plants, and poisoning has resulted.
What it really shows is folks who share country with game animals should always be aware of potential toxicity of all ornamentals. While browsers may not feed upon the yew for years, something can change their pattern and they will browse upon new plants without warning.
This is particularly true of deer, which are much more problematic during any kind of climatic anomaly. It’s also why some deer-proof plants get eaten … sometimes.
The major offender here is Japanese yew, which experts say is even more toxic than the English species. One study determined the lethal dosages in grams of raw yew for farm animals based on a long history of livestock poisoning, which proves just how little it takes to kill. For horses and sheep it’s 100 to 200 grams, dogs and poultry at just 30 grams, with pigs and cows in between.
Goats often get in fatal trouble browsing yews outside the edges of their pastures. This is true of bored or hungry horses that tend to chew wood as well as leaves. Be aware that the cuttings of pruned or sheared yews are equally dangerous as animals chew on the dead slash as well. It was the cause of three tortoise deaths after eating leaves that had fallen a year earlier, yet still contained enough to kill them.
Yews are far more common in colder regions due to their winter hardiness. However, they are all over Los Angeles, too, proving climate is no regulator of where they grow. If you’re in wild areas with game and already have them on your property, wrap securely with burlap each winter to discourage game. Otherwise, simply remove and replace with junipers or other less toxic evergreens.
While losing a herd of 50 antelope is bad enough, the real tragedy is they are poisoned. That means they can’t be harvested as they do in Maine and Alaska because this toxin could affect the meat. Let this be a lesson to everyone that plants are quite powerful things, and how they interact with your life and that of other creatures can cause painfully unexpected consequences.