GPS data loggers
Despite many studies on yellow-eyed penguins we know little about their habits at sea – their foraging patterns and where they are feeding and travelling. Interpretation of the species’ population dynamics, and consequently conservation measures, are primarily based on what can be observed on land. Today with the aid of modern satellite technology, studying penguin behaviour at sea through miniature GPS logging devices attached to their backs has opened a new window of opportunity to examine all aspects of the penguins’ biology.
The GPS-loggers are manufactured by a German company, earth&OCEAN Technologies, the only manufacturer able to make these to the required specifications. The Trust purchased three of these at an approximate cost of $15000 (funded by part of the 2002 Contact Energy ‘Community Conservation Challenge’ donation).
The loggers, which are activated by transmission to satellites, record the penguins’ dive depths at given intervals (usually 1 second) as well as their geographical position after each dive. The devices are attached using adhesive cloth tape, which allows for easy detachment without causing any damage to the penguin’s plumage. The average battery life of a GPS-logger is approximately 3 days (depending on battery life), so only short-term attachment is done.
In collaboration with the University of Otago’s Zoology Department and the Department of Conservation’s Southland Conservancy, the Trust attached these loggers on yellow-eyed penguins during periods of this year’s breeding season. These devices allowed us to record a bird’s geographic position as well as its dive behaviour. Trialled on three birds at Bushy Beach near Oamaru in 2003 by PhD student Thomas Mattern (pictured right), the results showed a ‘map’ of travel in which the penguins appear to use underwater landmarks to guide them to the best foraging areas.
In 2005, research was carried out on the Stewart Island population, which has different oceanographic environments to those off the Otago coastline. Yellow-eyed penguins breed mainly along the northern and north-eastern coast of Stewart Island where the shelf is located more than 100km offshore. This is a wide shelf area compared to the North Otago shallow and narrow continental shelf, which is less than 50km offshore.
By studying the foraging behaviour of yellow-eyed penguins breeding at locations with different oceanographic features, we may shed light on a greatly unknown component of their biology. This will allow better understanding of the species’ population status, and development of customised management strategies for the species’ different habitats.
