Rats, cats, and mustelids introduced to seabird nesting islands devastate breeding colonies — causing mass mortality with profound welfare consequences for animals with no evolutionary predator defense.
Seabirds on islands without evolved predator responses have no behavioral defenses against rats and cats. Chicks are killed in their burrows; eggs are consumed; incubating adults are attacked. The breeding failure is near-total in heavily infested colonies — birds return year after year to nest in environments that have become death traps. Individual suffering during predator attack — particularly the prolonged terror experienced by chicks killed by rats — represents welfare harm at scale that predator eradication programs directly address.