Why are California’s wild pigs turning blue inside? and what it means for the pork on your plate

Hunters in California have reported a disturbing phenomenon: wild pigs with “neon blue” flesh. The unusual cases were traced back to Monterey County, where authorities now warn of potential contamination risks in game animals consumed by humans.

Investigations by the California Department of Fish and Wildlife (CDFW) revealed that the blue coloration stems from rodenticide poisoning. The toxin, often dyed for identification, has been restricted in California since 2024.

In an advisory, CDFW Pesticide Investigations Coordinator Dr. Ryan Bourbour said, “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,”.


The chemical identified in recent cases is diphacinone, a first-generation anticoagulant rodenticide that causes severe internal bleeding.

What is Diphacinone?

Diphacinone was developed as a method to exterminate rodents. It is an anticoagulant with delayed effects, which is significant because it allows multiple rodents to consume the bait without immediately feeling threatened.

First invented in 1962, diphacinone was widely utilized across the United States to control rodent populations. The toxin works by preventing blood from clotting, ultimately leading to internal bleeding and death.

Unfortunately, while diphacinone is highly effective at killing the animals that ingest the bait, it can also unintentionally harm or kill other animals through secondary poisoning.

This poses a risk of exposure to humans as well. To address this concern, a safety feature was added to diphacinone: a blue dye that clearly indicates when an animal has consumed the toxin.

Risks to wildlife and humans

While diphacinone breaks down faster than more powerful second-generation rodenticides, it can remain active in animal tissues even after death, and cooking does not eliminate the risk.

This makes predators and humans vulnerable if they consume contaminated meat. Wildlife groups have long warned that pesticides, from owls to bees, harm non-target species by spreading through the food chain.

Similar cases were documented as far back as 2015. Wild pigs, omnivorous hybrids of domestic pigs and wild boars, often scavenge poisoned rodents or consume bait directly, increasing the chance of secondary poisoning.

According to a-z-animals, some potential health issues that may arise from eating meat contaminated with diphacinone include:

• Coughing up blood
  
• Blood in urine
  
• Bloody stools
  
• Nose bleeding
  
• Gum bleeding
  
• Excessive bruising
  
• Dizziness
  
• Abdominal pain
  
• Back pain
  
• Shortness of breath
  
• Blue skin coloration
  
• Low blood pressure
  
• Fever

Diphacinone is both an anticoagulant and a poison, which is why reports of animals found with diphacinone should be taken seriously. Before consuming any meat, it is important to test it for the presence of rodenticide to ensure it is safe to eat, regardless of whether it displays a blue color.