Do implanted data-loggers affect the time spent at sea by Little Penguins (Eudyptula minor) during winter?

Abdominally implanted data-loggers have been used to study the behaviour and physiology of birds, with no detectable negative effects. This technique has great potential for smaller and streamlined species, since these animals tend to be more prone to the negative effects that may be associated with externally attached devices. We conducted the first assessment of the impacts of abdominally implanted heart-rate data-loggers on a smaller species, the Little Penguin (Eudyptula minor), which weighs ∼1.1kg. The number and duration of trips to sea were recorded in male penguins implanted with a device (n≤10) and compared with a control group not implanted with a device (n≤10). Trips were recorded for the entire duration of the Penguins' winter non-breeding period, which for this species is the time of year when their energy budgets are most delicately balanced. The heart-rate data-loggers appeared to have no effect on percentage of time spent at sea, and the number and duration of overnight trips of 25 days or 626 days. Implanted Penguins undertook fewer trips of 1-day duration but the duration of these trips of 1 day was not affected. Individual Penguins showed highly variable foraging behaviour and the difference in the number of trips of 1 day may be attributed to individual specialisation in foraging behaviour. © 2010 Royal Australasian Ornithologists Union.