California Wild Pigs Found With Startling Neon Blue Flesh From Rodenticide

Game hunters in California have discovered striking ‘neon blue’ flesh inside wild pigs, leading authorities to warn of possible contamination.

“I’m not talking about a little blue,” Dan Burton, who owns a wildlife-control company, told Salvador Hernandez at The Los Angeles Times.

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

Local officials investigated the unusual colouring and determined that it resulted from rodenticide poisoning. They have consequently issued an alert across Monterey County.

Neon blue wild pigs linked to rodenticide in California

Rat poisons made with the chemical compound diphacinone are commonly coloured blue so they can be identified. California has placed tight restrictions on the compound since 2024.

Watch the video below for a summary:

“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.”

Worryingly, this is not the first instance of wild pigs in the area having blue-stained internal tissue.

Widely used for rodent control in agriculture, diphacinone is a first-generation anticoagulant rodenticide that causes extensive internal haemorrhaging.

It binds to an enzyme responsible for recycling vitamin K. As a result, less vitamin K is available, preventing animal livers from making sufficient clotting factors needed to stop internal bleeding.

Predators - humans included - can become unwell after consuming an animal poisoned by the toxin. Although diphacinone breaks down more quickly than second-generation rodenticides, it can stay active in a dead animal’s tissues for a period of time, including after cooking.

Diphacinone threatens wildlife beyond its intended targets

Wildlife organisations around the world have long called for less dependence on chemical pesticides because of the unintended harm they cause. Pesticides are damaging wildlife ranging from owls to bees.

Animals not targeted by these chemicals may eat them directly, or suffer secondary exposure by eating creatures that have consumed the poison. This places further pressure on species already at risk.

Diphacinone has been detected in numerous poisoned predators, including raptors, mountain lions, bobcats and foxes, alongside the endangered northern spotted owl and San Joaquin kit fox.

While the outlook is generally poor, anticoagulant poisoning in animals can be treated if it is identified before symptoms develop and vitamin K is given as an antidote.

Its destructive effects on wildlife were the reason California imposed strict controls.

“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.”

California’s wild pigs - hybrids of domestic pigs and European wild boars deliberately released a century ago - are voracious omnivores. They will readily consume both poisoned rodents and bait.

Since March this year, local trapper Dan Burton has seen several wild pigs make a point of seeking out rodenticide-laced oats used in squirrel traps.

The colouring agent apparently affects only the pigs’ fat, with their other tissues retaining their usual colour.

Pesticide exposure and safer pest-control options

Pesticides can also harm people who are exposed to them. They have been associated with lower sperm rates, diabetes, cancers, Alzheimer’s and other health conditions.

A recent US study found that chlorpyrifos, a widely used insecticide, produces structural abnormalities in the brain and reduces motor function in children and adolescents.

Many of these pesticides have been deployed on a large scale without sufficient long-term research into their effects on human health.

“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 seeks to reduce the hazards of such dangerous animal-control methods by using a combination of safer alternatives. These include supporting natural predators and installing fences, traps and other barriers, such as crawlspace vents.

Additional deterrents may involve carefully targeted light and sound, including playing talkback radio, or scents such as peppermint essential oil.

The CDFW asks anyone who finds blue animals or other abnormalities to notify the Wildlife Health Lab; details are here.

An earlier version of this article was published in August 2025.