Wild pigs in California turn ‘neon blue’, trigger warnings

Game hunters have found surprisingly ‘neon blue’ meat inside wild hogs in California, triggering advisory statements over possible contamination.

“I’m not talking about little blue,” Dan Burton, owner of a wildlife control company, told Salvador Hernandez. Los Angeles Times.

“I’m talking about neon blue, blueberry blue.”

An investigation by local officials determined that the dramatic color change was caused by rodenticide poisoning, prompting them to issue a warning in the Monterey County area.

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Rat poison containing the chemical compound diphasinone is sold in blue for identification. The use of the compound is highly restricted in California starting in 2024.

Watch the video below for a summary:

“Hunters should be aware that meat from game animals such as wild hogs, deer, bears and geese may be contaminated,” says Ryan Borber, pesticide research coordinator for the California Department of Fish and Wildlife (CDFW).

“Rodenticide exposure may be a concern for non-target wildlife where applications occur in close proximity to wildlife habitat.”

Worryingly, this is not the first time wild boars in the region have had blue insides.

A popular rodent control in agriculture, diphasinone 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 the animal’s liver to produce enough clotting factors to stop internal bleeding.

Predators, including humans, who eat poisoned animals can become ill themselves; While the chemical degrades more quickly than second-generation rodenticides, diphasinone remains active in dead animal tissue for some time, even after cooking.

Wildlife groups worldwide have long urged us to stop relying on chemical pesticides because of the collateral damage these toxins cause. From owls to bees, pesticides are wreaking havoc on wildlife.

Non-target animals either consume it directly or are affected by secondary exposure by eating other animals that ingest the poison, adding further stress to already endangered species.

Diphacinone is found in the systems of many venomous predators, including raptors, mountain lions, bobcats, foxes, as well as the endangered northern spotted owl and San Joaquin kit fox.

Although the prognosis is generally poor, anticoagulation toxicity in animals can be treated if caught before symptoms appear and vitamin K is given as an antidote.

But its devastating effects on wildlife prompted its strict control in California.

“Pesticide users are urged to take precautions when applying rodenticides so that wildlife is not exposed,” CDFW advises.

“Prior to application, it is important to ensure that non-target wildlife are not using the area where the pesticide is applied. It is also important to use appropriate bait stations and application methods that do not reach non-target species.”

California feral pigs—which are a hybrid between domestic pigs and European wild pigs that were deliberately released a century ago—are voracious omnivores, so they happily eat both poisoned rodents and bait.

Since March of this year, Dan Burton, a local trapper, has seen many feral hogs go out of their way to obtain rodenticide-infested oats used in squirrel traps.

The corresponding dye appears to affect only the pig’s fat, leaving the rest of their tissues normally colored.

Pesticides are also harmful to exposed humans. They are linked to decreased sperm rate, diabetes, cancer, Alzheimer’s, and other health conditions.

A recent US study found that the commonly used pesticide chlorpyrifos causes structural brain abnormalities and reduced motor function in children and adolescents.

Many of these pesticides have been used on a large scale without adequate long-term studies of their effects on human health.

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“Excessive and uncontrolled pesticide use results in food contamination as well as environmental, agricultural, and aquatic pollution,” concludes the 2024 Scientific Review on Pesticide Use.

“To address the global threat posed by pesticides, international coordination and cooperation among nations is essential.”

Integrated pest management aims to reduce the risk of such dangerous animal control practices by combining several safe strategies. This includes encouraging natural predators and building fences, nets and other barriers such as crawlspace vents.

Other animal distractions may include the targeted use of light and sound, such as playing a talkback radio, or applying scents, such as peppermint essential oil.

CDFW is urging anyone who encounters blue animals or other abnormalities to report them to the Wildlife Health Laboratory; Details are here.

A previous version of this article was published in August 2025.

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