Consistent foraging routes and benthic foraging behaviour in yellow-eyed penguins

Abstract

Yellow-eyed penguins Megadyptes antipodes seemingly forage at discrete marine locations over the continental shelf, where they are believed to feed predominantly at the seafloor. Such behaviour would distinguish them from most other penguin species that generally employ pelagic foraging strategies. From 2003 to 2005 we studied the foraging behaviour of yellow-eyed penguins breeding near Oamaru, New Zealand. We used 2 types of data loggers: GPS loggers recorded geographical position and dive depth at set intervals, while time-depth recorders (TDRs) recorded only dive depth. The penguins performed day trips (range: 12 to 20 km from the coast) or shorter evening trips (range: < 7 km). Consecutive foraging trips of individuals revealed remarkably consistent foraging routes. Birds travelled along similar -at times congruent -paths, markedly changed course at distinct locations, and revisited certain locations on separate trips, indicating skilful navigation. Three trip stages could be distinguished on one-day trips. During the outgoing (seaward travelling) and incoming (shoreward travelling) stages the birds followed linear courses. These stages were separated by a period of midday activity in which birds exhibited higher dive effort and often tended to stay within confined areas. The diving behaviour revealed an exclusive bottom-foraging strategy, with 87% of all dives being benthic dives; the majority of non-benthic dives occurred during the last 2 to 3 h of the trip, indicating primarily travelling behaviour. Furthermore, yellow-eyed penguins employ benthic dives not only when feeding but also frequently when travelling. We suggest that benthic dives might facilitate navigation and, consequently, account for the consistent foraging patterns of yellow-eyed penguins.

Advances in the tracking of marine species: using GPS locations to evaluate satellite track data and a continuous-time movement model

“…For example, an average of 51 in-water locations per day were acquired when tracking nesting loggerhead sea turtles Caretta caretta using an increased sampling rate (Schofield et al 2007). Mattern et al (2007) were able to receive on average a location every 2.7 min when tracking yellow-eyed penguins Megadyptes antipodes with GPS instruments, which closely matches the average dive durations measured.…”

Flexible foraging behaviour of a sexually dimorphic seabird: large males do not always dive deep

“…Dive data were analysed with custom-written software as described in Mattern et al (2007). Dive analysis encompassed identification of dive events and calculation of basic dive parameters for every dive.…”

Coupling GPS tracking with dive behavior to examine the relationship between foraging strategy and fine-scale movements of northern fur seals

“…For example, both gentoo Pygoscelis papua and Adélie penguins P. adeliae feed on epipelagic prey, whereas yellow-eyed penguins Megadyptes antipodes forage benthically (Croxall et al 1988, Naito et al 1990, Mattern et al 2007. Leatherback sea turtles Dermochelys coriacea feed on epipelagic, soft-bodied invertebrates such as jellyfish, whereas mature green turtles Chelonia mydas feed primarily on benthic sea grasses and algae (Hochscheid et al 1999, Hays et al 2006.…”