Survival at sea
Blue penguins have many adaptations ensuring their survival at sea. They have special salt glands located above the eyes allowing them to excrete excess salt they ingest with their food.
The feathers are particularly important for ensuring the penguins stay warm enough at sea. The outer part of the feathers are hard and act as a wind-breaker, the penguins use oil from a gland near their tail to waterproof the outer part of the feathers. The inner part of the feather is downy and traps a layer of insulating air.
Underneath the skin the penguins have a layer of fat which also helps to keep them warm.
Blue penguins at Oamaru eat mainly slender sprat; a small, schooling, inshore fish. When foraging at sea the penguins dive on average 800 times a day and mostly feed in the top 10m of the water column, staying under the water only 20-30 seconds at a time. They can swim up to 8km per hour and during the breeding season cover on average 50km in a day.
The penguins have a very strong bite, a hook on the end of their bill and have spiny spikes on their tongues pointing towards the back of the mouth, all these features help them to hold and swallow slippery prey.
Predators of blue penguins at sea are sharks, sea-lions and leopard seals. The dark blue feathers on the penguins backs help to hide them when predators look down into the dark water. The white feathers on their underside merge them with the lighter water as the predator looks up.