When the Forest Turns Toxic

Bright Blue Flesh in California Wild Pigs Traces Back to the Ingestion of Dyed Rodenticide

Photo from Wikimedia Commons / CC BY-NC-ND 2.0

A startling discovery in Monterey County, Calif. has put hunters, wildlife officials and conservationists on high alert: wild pigs with bright blue colored flesh and internal organs. The freaky phenomenon has now been confirmed by the California Department of Fish and Wildlife ( CDFW) and multiple news outlets. 

In March 2025, a wildlife trapper in Monterey County reported several pigs showing unusual blue muscle and fat, an observation that started a formal investigation. Lab tests at CDFW Wildlife Health Lab and the California Animal Health and Food Safety Laboratory in Davis confirmed the presence of rodenticide Diphacinone in the liver and stomach contents of one of the affected pigs. 

The culprit appears to be dyed rodenticide bait, typically used by farmers and pest control operators to manage rodents, that wild pigs ingested directly or via contaminated prey. The dye stains fat, muscle and internal organs after digestion, producing the vivid blue color. 

The poison is highly toxic not only to pigs, but also to other wildlife. As an anticoagulant, Diphacinone interferes with the body’s ability to clot blood, increasing risk of fatal internal bleeding in exposed animals. 

Hunters have been warned to steer clear of any wild pig, deer, bear or goose with blue tissue. The coloration is a warning sign of contamination. CDFW officials say that any animal with discoloration should not be consumed. 

The danger extends beyond the hunted pigs. Predators or scavengers, including raptors, foxes, bobcats and others that feed on poisoned carcasses risk secondary poisoning, which raises broader ecological food concerns. 

In response, CDFW has issued statewide advisories suggesting that hunters, farmers and pesticide applicators remain vigilant. Under current regulations, Diphacinone use was largely banned in 2024, but there are still agricultural exemptions. Tighter controls and more responsible application practices, including the use of secure bait stations and integrated pest management are being implemented to minimize risk to non-target wildlife.

Officials say that while bright blue coloration is a confirmed sign of rodenticide ingestion, the absence of discoloration does not guarantee safety: animals may still be toxic even if their meat looks normal. 

As the studies continue, the warnings also uncover deeper environmental and public health concerns from wildlife mortality to food chain contamination and human exposure.