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A black-backed jackal at Addo Elephant National Park in South Africa, where the remains of dozens methomyl-poisoned jackals were recently found. Image: Arthur Chapman, Flickr.

Earlier this month, officials at South Africa's third-largest national park, the Addo Elephant National Park in the country's Eastern Cape, began making some grisly discoveries: multiple carcasses of black-backed jackals were found strewn along a 17km stretch of road within its borders, the cause of death a mystery. But toxicology reports carried out on tissue samples taken from the dead animals soon brought some answers. The jackals had been killed by poison. The culprit? A highly toxic insecticide known as methomyl.  

When it comes to poisons, methomyl is no lightweight. The US Environmental Protection Agency (EPA) labels it a 'Class 1' toxin, with "high acute toxicity to humans". Symptoms of exposure make for a scary list: even small doses can cause weakness, blurred vision, chest discomfort and muscle tremors. Severe exposure can be deadly. Not surprisingly, the pesticide is also highly toxic to wildlife, including fish, birds and non-target insects like bees, and it's been found to contaminate groundwater. Despite these hazards, products containing methomyl remain in use, mainly for the control of various crop pests, in more than 70 countries – including in South Africa and the US (although in both countries its use is restricted).

And South Africa is not the only place where the poison has been making headlines. Back in 2012, a Greenpeace investigation exposed dangerously high traces of methomyl on Lipton herbal tea products being sold at markets in China (the pesticide is banned for use in tea production by the Chinese Ministry of Agriculture). That same year, consumer groups called for the poison to be banned in the Philippines after laboratory tests found high residues of methomyl on vegetables.

In the case of the poisoned jackals in South Africa, the animals almost certainly died as a result of illegal use of the pesticide – park officials still need to complete their investigations, but they suspect the poisoning was deliberate and malicious since toxins like methomyl are never legitimately allowed to cross into the park. Still, the deaths serve to illustrate just how devastating the poison's effects can be.

Methomyl misuse that targets wildlife is a problem in the US as well, where methomyl-laced fly bait granules mixed with cola are often used by home owners to control 'nuisance' wildlife like raccoons, a tactic that's both illegal and deadly to any number of animals (wild or domestic) that may come into contact with the lethal concoction. 

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The Center for Biological Diversity is seeking protection from dangerous pesticides for 119 endangered and threatened species throughout the US, including animals like the black-footed ferret. Image: USFWS Mountain-Prairie.

But even when used legally, pesticides like methomyl have the potential to do irreparable harm to ecosystems and wildlife, and particularly to endangered species. Just a few weeks ago, a major conservation NGO in the US, the Center for Biological Diversity, succeeded in its demands for that country's government to analyse the impacts of five common pesticides – including methomyl – on endangered wildlife across the nation.

"We don’t think these chemicals should even be in use, but at the very least, measures to protect endangered wildlife should have been put in place when these chemicals were first approved," said the center's attorney Collette Adkins Giese at the time.  

With that win under its belt, the Center's fight against the irresponsible use of pesticides in the US is continuing. Its legal team recently fought a round in a San Francisco court as part of the most comprehensive legal action yet to protect threatened animals from pesticides. The organisation wants wildlife authorities in the US to assess the impacts of dozens of pesticides on 119 endangered and threatened species – including Florida panthers, California condors, piping plovers, black-footed ferrets, arroyo toads, Indiana bats and Alabama sturgeon.

"For decades, the EPA has turned a blind eye to the disastrous effects pesticides have on America’s rarest species," said Giese in a statement. "With more than a billion pounds of pesticides applied each year in this country – the highest pesticide usage rate in the world – the harms to America’s endangered wildlife are enormous."

Back in South Africa, the number of jackal carcasses found in Addo Elephant National Park has grown from an initial count of 21 to 36. Dead crows have also been found (along with bat-eared foxes, though this is unconfirmed). So far, attempts to track down the source of the pesticide have failed, and there is fear that the poison, which can take up to 90 days to break down, may continue spreading to other animals as scavengers feed off contaminated carcasses. 

Top header image: CIAT, Flickr