Consistent Site-Specific Foraging Behaviours of Yellow-eyed Penguins/Hoiho Breeding on Stewart Island, New Zealand

Abstract

The endangered yellow-eyed penguin/hoiho (Megadyptes antipodes) predominantly forages benthically within its mainland range and shows high foraging site fidelity. Identifying consistencies in foraging locations can allow effective conservation, especially when managing bycatch risk. This study investigated the at-sea distribution of penguins breeding on Stewart Island to explore site-specific foraging strategies and inform fisheries management. During the 2020/21 season, 19 adult breeding yellow-eyed penguins from Port Pegasus, Paterson Inlet, and Codfish Island were fitted with GPS-TDR dive loggers to track their movements and diving behaviours. A total of 25,696 dives were recorded across 91 foraging trips. Birds from Port Pegasus reached significantly greater depths, spent longer at the seafloor, and performed longer dives. They also had the smallest foraging distribution, with most activity concentrated inshore. Compared to Port Pegasus, foraging radii and trip lengths were twice as large for Paterson Inlet and four times larger at Codfish Island. Despite differences in available foraging habitat, considerable individual and intra-site consistency for preferred foraging locations was observed. Localised behaviour and inter-site differences in dive metrics suggest significant plasticity in foraging ecology across their mainland range; however, individual behaviour and preferred foraging locations were extremely predictable. Thus, risk of mortality from fisheries can be quantified and managed accordingly.

Staying close to home: Marine habitat selection by foraging yellow-eyed penguins using spatial distribution models

“…However, quantification of these threats and dynamic processes or temporal variability (e.g., after extreme weather events, El Niño Southern Oscillation) is not easily represented in species distribution models. For instance, since there is little evidence that foraging distances have changed significantly over time (Ellenberg and Mattern, 2012;Muller et al, 2021;Elley et al, 2022;Young, 2022), studies comparing diving behaviour (e.g., dive depth, bottom time) and diet over time may more clearly identify patterns of environmental change. Additionally, high quality environmental and commercial fisheries data are often unavailable or inaccessible, and the overall risk from fisheries interactions (e.g., overfishing, bycatch) remains largely unknown.…”

“…While penguin habitat use may be different throughout the year, their tolerance for certain environmental conditions might remain consistent. Several studies have analysed yellow-eyed penguin diving behaviour (Mattern et al, 2013;Mattern et al, 2007;Chilvers et al, 2014;Muller et al, 2020;Elley et al, 2022) and foraging range (Moore et al, 1995;Moore, 1999;Muller et al, 2021;Young et al, 2022). However, this is the first study that investigates the environmental drivers influencing marine habitat selection.…”

“…By quantifying the current distribution of yellow-eyed penguins and identifying the environmental predictors that best explain their patterns of marine habitat use, we can anticipate the impacts of future environmental change, predict how penguins might adapt or respond to such changes, and inform specific, effective conservation methods to avert localised extinctions. several projects and collated for the purpose of this research (Mattern, 2006;Mattern et al, 2007;Mattern et al, 2013;Mattern, 2020;Elley et al, 2022;Young, 2022), including Department of Conservation's Conservation Services Programme contracts (POP2016-05, POP2018-02, and POP2020-05). Fieldwork was conducted at 22 colonies across the South Island, New Zealand, including Stewart Island and Codfish Island/Whenua Hou (Figure 1).…”

“…70 g). For data collected after 2016 (Elley et al, 2022;Young, 2022), Axy-Trek marine GPS-TDR loggers were used (Technosmart, Rome, Italy). The Axy-Trek loggers varied in size (L x W x H = 65 x 39 x 14 mm or 69 x 40 x 14 mm) and mass (46-59 g) depending on battery size.…”