Diving

Little penguins are expert divers and can easily dive to 50m whilst holding their breath for about 1.5 minutes.  They prefer, however, to dive to about 13 m for about 45 seconds.  Researchers from SARDI placed some dive loggers on the backs of some little penguins from two different island colonies.  The little penguins from both islands spent most of their time diving to about 13m, however the loggers showed different shaped dives from the two islands.  One island was surrounded by shallow water and some penguins dived to the bottom, swam along the bottom and then sped up to the surface (see graphs).  This is called a U-shaped dive. These few birds were probably catching young fish in the seagrass nurseries on the sandy seafloor.  The penguins from the other island, which was surrounded by deep water, did more V-shaped dives, where they dived down and then came straight back again because they never reached the bottom.  Fishing in deep water can be less successful because fish can sometimes escape by swimming deeper than the penguins can dive.  Occasionally we can see where a penguin has encountered a fish, and chased it at great speed to almost 50 m before speeding straight back to the surface (see graphs).  Penguins that live in shallow water therefore are likely to have better fishing success.

Dive loggers also record light levels, and we can see from the graphs below that penguins do not dive until the light levels are quite high.  This is because little penguins cannot see or fish in the dark.  They leave the colony just before dawn to give them time to swim out to the fishing ground before the sun rises when they can begin diving.  Little penguins dive constantly throughout the day, which means that when they are moving to new fishing areas, they are diving the whole way, always keeping an eye out for fish.