The effect of carrying devices on breeding royal penguins

The impact of Time Depth Recorders (TDRs) and VHF transmitters, deployed on Royal Penguins (Eudyptes schlegeli) to examine foraging behavior, was assessed during all stages of the breeding season. Models of the devices were attached to penguins and compared to control birds with no devices. There were no impacts from transmitters on probability of return from a foraging trip, foraging trip duration, mass gained, water influx, or body composition, but substantial impacts from the TDRs. Attachment of TDRs (1) reduced the likelihood that penguins would continue the breeding attempt, (2) increased foraging trip duration, (3) increased water influx, and (4) decreased fat levels. The effects varied with sex and stage in the breeding season, which appeared to be related to the energetic demands of the stage in the breeding season. TDRs probably increased drag, affecting swimming speed and foraging success. The differential impact of the devices is most likely related to their cross-sectional area and streamlining, with TDRs being larger and less streamlined than transmitters.