Game hunters have found startlingly ‘neon blue’ flesh inside of wild pigs in California, triggering advisory statements on potential contamination.
“I’m not talking about a little blue,” Dan Burton, owner of a wildlife control company, told Salvador Hernandez at The Los Angeles Times.
“I’m talking about neon blue, blueberry blue.”
An investigation by local authorities found the dramatic color change was caused by rodenticide poisoning, prompting them to issue a warning throughout the Monterey County area.
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Rat poisons containing the chemical compound diphacinone are often sold dyed blue for identification. The compound’s use has been highly restricted in California since 2024.
Watch the video below for a summary:
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“Hunters should be aware that the meat of game animals, such as wild pig, deer, bear, and geese, might be contaminated if that game animal has been exposed to rodenticides,” says pesticide investigations coordinator Ryan Bourbour from the California Department of Fish and Wildlife (CDFW).
“Rodenticide exposure can be a concern for non-target wildlife in areas where applications occur in close proximity to wildlife habitat.”
Concerningly, this isn’t the first time wild pigs in the region have had their innards tainted blue.
A popular rodent control in agriculture, diphacinone is a first-generation rodenticide that acts as an anticoagulant, causing severe internal bleeding.
It works by binding to an enzyme that recycles vitamin K. This reduces available vitamin K, making it impossible for animal livers to produce enough of the clotting factors crucial to prevent internal bleeding.
Rodenticide bait. (CDFW)
Predators, including humans, who eat an animal poisoned with the toxin can become ill themselves; while the chemical breaks down faster than second-generation rodenticides, diphacinone remains active in the dead animal’s tissues for some time, even if it’s cooked.
Wildlife groups globally have long been urging us to stop relying on chemical pesticides because of the collateral damage these poisons inflict. From owls to bees, pesticides are causing great harm to wildlife.
Non-target animals either consume it directly or are impacted by secondary exposure when eating other animals that have ingested the poison, adding further strain on already endangered species.
Diphacinone has been found in the systems of many poisoned predators, including raptors, mountain lions, bobcats, foxes, as well as the endangered northern spotted owl and San Joaquin kit fox.
Though prognosis is typically poor, anticoagulation poisoning can be treated in animals if caught before symptoms appear and vitamin K is administered as an antidote.
But this devastating impact on wildlife is what prompted its strict control in California.
“Pesticide applicators are urged to take measures when applying rodenticides so as not to expose wildlife,” the CDFW advises.
“Prior to application, it is important to ensure non-target wildlife are not using the area where the pesticide is to be applied. It is also important to use appropriate bait stations and application methods that exclude access to non-target species.”
A wild pig with blue innards discovered in 2015. (GlendilTEK/imgur)
California’s wild pigs — which are hybrids between domestic pigs and European wild boars that were intentionally released a century ago – are voracious omnivores, so would happily eat both the poisoned rodents and the bait.
Since March this year, a local trapper, Dan Burton, observed multiple wild pigs going out of their way to obtain oats baited with rodenticide, used in squirrel traps.
The associated dye appears to affect only the pigs’ fat, leaving the rest of their tissues normally colored.
Pesticides are harmful to exposed humans as well. They have been linked to declining sperm rates, diabetes, cancers, Alzheimer’s, and other health conditions.
The meat of a contaminated pig remains a standard pink, while the fat is stained blue. (GlendilTEK/imgur)
A recent US study found that the commonly used insecticide chlorpyrifos causes structural brain abnormalities and reduced motor function in children and adolescents.
Many of these pesticides have been used at large scales without adequate long-term studies of their impacts on human health.
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“Excessive and uncontrolled pesticide use resulted in food contamination as well as environmental, agricultural, and aquatic pollution,” a 2024 scientific review on pesticide use concludes.
“To address the worldwide threats posed by pesticides, international coordination and cooperation between nations are essential.”
Integrated pest management aims to mitigate the risks of such dangerous animal control practices by combining multiple safer strategies instead. These include encouraging natural predators and constructing fences, traps, and other barriers, like crawlspace vents.
Other animal deterrents can include the targeted use of light and sound, such as playing talkback radio, or applying scents, such as peppermint essential oil.
The CDFW is urging anyone who encounters blue animals or other abnormalities to report them to the Wildlife Health Lab; details are here.
An earlier version of this article was published in August 2025.