Macaroni penguins are the world's most numerous penguin species but face accelerating population decline driven by krill availability collapse linked to both climate change and commercial harvesting pressure.
Macaroni penguins experiencing prey scarcity during breeding suffer the compound welfare cost of extended foraging trips, reduced chick provisioning, and eventual chick starvation in poor years. Adults that invest significant energy in the 5,000 km round-trip migration to breeding grounds then face inadequate local prey face severe physiological stress. Chicks that receive insufficient food develop slowly, are more vulnerable to cold and predation, and often die before fledging. Colony-level breeding failures, while representing population loss, also represent the accumulated welfare cost of thousands of individual animals whose breeding investment returns nothing. The geographic concentration of krill harvesting near sub-Antarctic penguin colonies compounds natural climate-driven prey scarcity.