RESUMO
Rapid environmental changes can dramatically and durably affect the animal's foraging behavior. In the Ross Sea (Antarctica), calving of the Nansen Ice Shelf in 2016 opened a newly accessible marine area of 214 km2. In this study, we examined the foraging behavior of Adélie penguins from the nearby Inexpressible Island in December 2018, by tracking 27 penguins during their at-sea trips using GPS, depth and video loggers. The penguins mainly foraged within 88.2 ± 42.9 km of their colony, for 23.4 ± 6.8 h. Five penguins headed south to the newly exposed habitat along the Nansen Ice Shelf, whereas 22 penguins exploited previously available foraging areas. There was no significant difference in any of the foraging trip or diving parameters between the two penguin groups; however, in the calved region the penguins were diving into shallow areas more often than did the other penguins. These results show that Adélie penguins on Inexpressible Island had explored the newly exposed area after calving. We conclude that the penguins respond to newly available habitat following stochastic environmental events, either through information sharing at the colony, and/or by balancing prey availability per capita across the foraging sites. Considering that this penguin breeding area is under investigation for the establishment of an Antarctic Specially Protected Area (ASPA), the results of this study may provide insights for evaluating the ecological importance of this area and formulating an ASPA management plan for conservation.
Assuntos
Comportamento Alimentar , Spheniscidae , Animais , Regiões Antárticas , EcossistemaRESUMO
Theory predicts that sympatric predators compete for food under conditions of limited resources. Competition would occur even within the same species, between neighboring populations, because of overlapping foraging habits. Thus, neighboring populations of the same species are hypothesized to face strong competition. To test the hypothesis that intra-specific competition is more intense than inter-specific competition owing to a lack of niche partitioning, we estimated the foraging area and diving depths of two colonial seabird species at two neighboring colonies. Using GPS and time-depth recorders, we tracked foraging space use of sympatric breeding Chinstrap and Gentoo penguins at Ardley Island (AI) and Narebski Point (NP) at King George Island, Antarctica. GPS tracks showed that there was a larger overlap in the foraging areas between the two species than within each species. In dive parameters, Gentoo penguins performed deeper and longer dives than Chinstrap penguins at the same colonies. At the colony level, Gentoo penguins from NP undertook deeper and longer dives than those at AI, whereas Chinstrap penguins did not show such intra-specific differences in dives. Stable isotope analysis of δ13C and δ15N isotopes in blood demonstrated both inter- and intra-specific differences. Both species of penguin at AI exhibited higher δ13C and δ15N values than those at NP, and in both locations, Gentoo penguins had higher δ13C and lower δ15N values than Chinstrap penguins. Isotopic niches showed that there were lower inter-specific overlaps than intra-specific overlaps. This suggests that, despite the low intra-specific spatial overlap, diets of conspecifics from different colonies remained more similar, resulting in the higher isotopic niche overlaps. Collectively, our results support the hypothesis that intra-specific competition is higher than inter-specific competition, leading to spatial segregation of the neighboring populations of the same species.
RESUMO
In contrast to their terrestrial call, the offshore call of penguins during their foraging trips has been poorly studied due to the inaccessibility of the foraging site-the open ocean-to researchers. Here, we present the first description of the vocal behaviour of penguins in the open ocean and discuss the function of their vocal communication. We deployed an animal-borne camera on gentoo penguins (Pygoscelis papua) and recorded their foraging behaviour during chick guarding. From the video recordings, we collected 598 offshore calls from 10 individuals in two breeding seasons (2014-2015 and 2015-2016), and we analysed the acoustic characteristics and behavioural contexts of these calls, including diving patterns, group association events, and foraging behaviour. The offshore calls varied in their dominant frequency and length, and penguins produced calls of different lengths in succession. Group associations were observed within one minute following an offshore call in almost half of the instances (43.18%). Penguins undertook dives of shallower depths and shorter durations after producing an offshore call than those before producing an offshore call. Our findings show that penguins may use vocal communication in the ocean related with group association during foraging trips.