Managing Mediterranean soil resources under global change: expected trends and mitigation strategies

Regional Environmental Change - The soils of the Mediterranean Basin are the products of soil processes that have been governed by a unique convergence of highly differentiated natural and...     

Foraging strategies of male Adélie penguins during their first incubation trip in relation to environmental conditions

Knowledge of habitat use by top marine predators in response to environmental conditions is crucial in the current context of global changes occurring in the Southern Ocean. We examined the at-sea locations of male Adélie penguins (Pygoscelis adeliae) breeding at Dumont d’Urville during their first, long incubation trip. Compared with the chick-rearing period, penguins performed longer trips, going to oceanic waters as far as 320 km from the colony. We observed 3 strategies: (1) five individuals covered large distances to the north, targeting open-ocean areas and following the currents of two persistent eddies; (2) five individuals foraged to the north-west, close to the Antarctic shelf slope at the limit of the pack ice; and (3) three individuals covered much shorter distances (northwards or eastwards). The foraging range also seemed to be limited by the body condition of the penguins before their departure to sea.     

Differential effects of increased corticosterone on behavior at the nest and reproductive output of chick-rearing Adélie penguins

Glucocorticoid hormones (GCs) are important mediators of physiological and behavioral responses to stress. While many studies have evaluated the environmental, behavioral, or physiological correlates of GCs and their effects on reproductive performances, further work is needed to clarify the relationship between GCs and fitness. Assessing the effects of increased GC levels on specific behaviors of breeding animals should improve our understanding of how GCs affect parental care. In this experimental study, we measured the effects of an experimental increase in corticosterone (CORT, the main avian GC) levels on the behavior of free-living male Adélie penguins (Pygoscelis adeliae) within the colony, their reproductive output, and the indirect consequences of both on the behavior of their partners. We show that increased CORT levels in males decreased their foraging time at sea while increased their attendance at the nest, although their attentiveness toward the nest itself decreased. In addition, treated males spent more time on comfort behaviors (e.g., preening), vocalizing, and engaging in positive social interactions relative to controls. Treatment further affected the behavior of their partners, but not chick begging and feeding rates. Penguins with increased CORT levels also exhibited decreased reproductive output. Previous studies of Adélie penguins in different life history stages and environmental conditions suggest that the consequences of CORT treatment on reproductive performance are context-dependent. In addition to the potential delay in the effects of increased CORT levels on reproduction, this context dependence should be taken into account when studying the behavior of free-living animals in relation to stress-inducing situations.     

Fatty acid evidence for the importance of myctophid fishes in the diet of king penguins, Aptenodytes patagonicus

We tested the usefulness of the fatty acid signature-method in investigating the diet of seabirds in conjunction with the conventional technique of stomach-content analysis. We compared the fatty acid composition of subcutaneous white adipose tissue (SWAT) of king penguin chicks (Aptenodytes patagonicus) during fattening periods to that of total lipids from their food. In both spring and autumn, the fatty acid composition of chick SWAT was identical to that of the dietary lipids. Because the diet of adult king penguins feeding for self-maintenance (i.e. not for their chicks) was essentially unknown, we subsequently analysed their SWAT fatty acid patterns after premolting and prebreeding foraging trips (during which they build up large energy reserves). The fatty acid composition of SWAT from adults was identical to that of chick adipose tissue and food. King penguin diet and SWAT were characterized by high levels of very long-chain mono-unsaturated fatty acids (20 to 24 carbon atoms, 16 to 23% by mass) and (n-3) poly-unsaturated fatty acids (19 to 27%); these consisted mainly of 20:1n-9 (5 to 8%) and 22:1n-11 (5 to 8%), and 22:6n-3 (10 to 13%) and 20:5n-3 (3 to 9%), respectively. Prey items identified from chick stomach contents indicated that the bulk of the food was oceanic myctophid fishes, mainly Electrona carlbergi, Krefftichthys anderssoni and Protomyctophum tenisoni. The fatty acid composition of four other species of myctophid fishes was similar to that of penguin diet and SWAT, but markedly different from that measured for a squid species and that reported for crustaceans. These findings indicate that adult king penguins prey on myctophid fish not only to feed their chicks but also for their own nutrition. The fatty acid signature-technique is therefore a reliable method to gain information on the food and feeding ecology of seabirds when more conventional techniques are of limited value. Such information is important to the understanding of trophic relationships between key species of the ecosystems, and also to provide insight into the nature of avian adaptations to the marine environment. Received: 11 December 1997 / Accepted: 25 July 1998