Seasonal Foraging Ranges and Travels at Sea of Little Penguins Eudyptula minor, Determined by Radiotracking

Abstract

The travels at sea, and by implication the foraging ranges, of Little Penguins Eudyptula minor from Phillip Island, Victoria, were examined within a period of 18 months in the first seasonal radiotelemetric study of penguins at sea. Two typical travelling patterns are evident: short-term, localised trips of a single day's duration; and long-term trips of several or many days duration and up to many hundreds of kilometres away from the burrow site. Each Little Penguin was capable of both kinds of trip; short-term trips were typical during the breeding season and long-term trips typical during the non-breeding season. Birds undertaking long-term trips generally had lower body masses than birds doing short-term trips. Port Phillip Bay was a favoured destination for long-term trips during winter. In other seasons, long-term trips elsewhere of up to 710 kilometres away from the burrow were recorded. On short-term trips, the mean maximum radius of travel was 7.9 km from the burrow and 95% of the recorded penguin-time was within a radius of 15 km of the burrow and 9 km of the coast. When prey was scarce Little Penguins appeared to range further on short-term trips. The mean net travelling speed on short-term trips was 1.5 km^-1 (range 0-6.9 km.h^-1, measured over 0.5 h intervals), and 0.7 kmkl on long-term trips (range 0.01-3.3 km.h^-1 measured over 21-126 h), although one penguin travelled at least 113 km in 34.5 h. On longterm trips, in the open sea of Bass Strait, about 74% of the records of telemetered Little Penguins were within 20 km of the coast. For the benefit of wildlife managers, I predict three zones that should contain most of the activity of Little Penguins from southern Phillip Island, including birds from the internationally known 'Penguin Parade'.