Here’s why owls are dying around illegal marijuana farms in California

The anticoagulant rodenticide, a poison aimed at, you guessed it, rats, has long been documented to have negative effects on other wildlife which get inadvertently poisoned along with the rats and mice.

Most of the studies on the effects of AR have been in urban and semi-urban settings where wildlife are most likely the non-targeted group. But in recent years, the use of AR has become more common in places in remote forest settings in the western United States.

Specifically, the widespread use of illegal clandestine marijuana cultivation sites on public and tribal lands have been a significant source of wildlife exposures in California.

A new study by scientists at the University of California Davis and the California Academy Sciences  have found the circle of life and the circle of death that has led to the cause of unnatural death for owls who have been found dead near the illegal crops.

The bodies of owls, including the northern spotted owls, have been tested in the northwestern California counties of Humboldt, Mendocino and Del Norte and found they’ve been tainted by the rat poison.

The northern spotted owl is of particular concern because of its vital conservation importance. The NSO is listed as threatened under the California Endangered Species Act.  Initially their loss of population was linked to the loss of their habitat. But the northern spotted owl now has a number of fronts to fight in order to survive. One of the challenges to their viability is having to compete with the barred owl BO which has moved into California from its historical range in eastern North America.

The barred owl and the northern spotted owl now compete for habitat and food in California which has also seen an increase in the number of illegal marijuana farms spring up.

About 40 per cent, or 34 of the 84 dead barred owls collected by the scientists, tested positive for AR. The rodenticide reduces the ability of animals to clot blood leaving them with internal bleeding and ultimately death. The number was even higher among the northern spotted owl. Of the 10  NSO carcasses examined by the scientists, seven of them had been exposed to AR.

Like people, rodents and mice are attracted to the aroma of the marijuana and the rodenticide is used to try and deter them from consuming the plant. All animals head to where the food is to be found. For rats and mice, that food mecaa are the illegal marijuana farms in remote areas in California. For hungry owls, who feed on the rats and mice, that becomes their go-to spot to find the food which ultimately kills them.


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Peg Fong is also in recovery from newspapers

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