Chickens may kill each other due to stress, overcrowding, pecking order disputes, or health issues, leading to aggressive behavior and injury.
Chicken cannibalism is a disturbing but common behavior where birds peck, wound, or kill flockmates. This aggressive behavior stems from natural instincts gone wrong under poor conditions. Understanding why chickens attack each other helps prevent costly losses.
Primary Causes of Chicken Cannibalism
1. Overcrowding and Stress
Chickens need adequate space to establish territories. The recommended minimum is:
| Bird Type | Age | Space Needed |
|---|---|---|
| Large breeds | 8-16 weeks | 1.5 sq ft/bird |
| Bantams | All ages | 0.75 sq ft/bird |
Overcrowding triggers stress that leads to feather pecking and vent pecking. Rhode Island Reds, a common backyard breed, are particularly prone to aggression when crowded.
2. Establishing Pecking Order
Chickens naturally create a social hierarchy. Violent fights may occur when:
- Introducing new birds to an established flock
- Mixing different ages or breeds
- Removing dominant birds
As noted in our article on introducing chickens to a new coop, gradual introductions prevent deadly conflicts.
3. Nutritional Deficiencies
Key dietary imbalances that cause aggression:
- Protein deficiency (especially methionine)
- High-energy, low-fiber diets
- Mineral shortages (salt, calcium)
According to Penn State Extension, nutritional deficiencies account for 30% of cannibalism cases.
Less Common But Serious Causes
4. Bright Lighting
Excessive light (over 16 hours daily) or intense bulbs (above 40 watts) increases pecking behavior. Red bulbs are safer than white for brooders.
5. Boredom and Lack of Enrichment
Chickens with nothing to peck except flockmates develop bad habits. Provide:
- Hanging greens
- Scratch grains in litter
- Perches at varying heights
6. Injury or Illness
Chickens instinctively attack weak flockmates. Blood draws immediate pecking that can turn fatal. Isolate injured birds immediately.
Prevention Strategies
Environmental Controls
- Maintain proper temperature (95°F for chicks, decreasing 5°F weekly)
- Ensure adequate feeder/waterer space (1 linear inch per bird)
- Provide nest boxes (1 per 5 hens) with dim lighting
Behavioral Interventions
When pecking starts:
- Apply anti-peck sprays to wounds
- Use pinless peepers (blinders) on aggressive birds
- Re-evaluate flock density and enrichment
For severe cases, consider the methods in our guide on stopping chickens from pecking.
When Cannibalism Turns Deadly
Fatal attacks typically involve:
- Vent pecking leading to prolapse
- Head pecking causing brain damage
- Sustained attacks on subordinate birds
One backyard chicken keeper reported: “Found one hen dead, with no visible injuries. Another lying three feet away, barely able to walk, with blood on top of her head.” This matches classic cannibalism patterns.
Special Considerations
Breed Differences
Some breeds are more aggressive:
- Rhode Island Reds
- Gamefowl varieties
- Crested breeds (Polish, Houdans)
According to Backyard Chickens forums, mixed flocks often see more violence than single-breed groups.
Age Factors
Peak danger periods:
- 4-8 weeks (feather development)
- 16-20 weeks (sexual maturity)
- During molts (feather regrowth)
Proper management reduces cannibalism risks significantly. Address issues promptly at the first signs of feather pecking or aggression to prevent escalation.