Effects of Individual Pre-Fledging Traits and Environmental Conditions on Return Patterns in Juvenile King Penguins

Despite the importance of early life stages in individuals' life history and population dynamics, very few studies have focused on the constraints to which these juvenile traits are subjected. Based on 10 years of automatic monitoring of over 2500 individuals, we present the first study on the effects of environmental conditions and individual pre-fledging traits on the post-fledging return of non-banded king penguins to their natal colony. Juvenile king penguins returned exclusively within one of the three austral summers following their departure. A key finding is that return rates (range 68–87%) were much higher than previously assumed for this species, importantly meaning that juvenile survival is very close to that of adults. Such high figures suggest little juvenile dispersal, and selection occurring mostly prior to fledging in king penguins. Pre-fledging conditions had a strong quadratic impact on juvenile return rates. As expected, cohorts reared under very unfavourable years (as inferred by the breeding success of the colony) exhibited low return rates but surprisingly, so did those fledged under very favourable conditions. Juvenile sojourns away from the colony were shorter under warm conditions and subsequent return rates higher, suggesting a positive effect of climate warming. The longer the post-fledging trip (1, 2 or 3 years), the earlier in the summer birds returned to their natal colony and the longer they stayed before leaving for the winter journey. The presence of juveniles in the colony was more than twice the duration required for moulting purposes, yet none attempted breeding in the year of their first return. Juvenile presence in the colony may be important for acquiring knowledge on the social and physical colonial environment and may play an important part in the learning process of mating behaviour. Further studies are required to investigate its potential implications on other life-history traits such as recruitment age

Brood patch temperature during provocation of incubating common eiders in Ny-Ålesund, Svalbard

In this short note we describe the behaviour and body changes of three incubating female common eiders (Somateria mollissima) during provocation made by humans approaching the nest. The study site was near the settlement of Ny-Ålesund, Svalbard. Temperture transmitters were implanted subcutaneously at the brood patch and data recorded using a VHF receiver. We found that the female experiment exhibited a passive defence response (“freezing”), accompanied by a significant drop in brood patch temperature (0.6 °C) during provocation; this temperature drop lasted for 5 minutes. These accord with other studies of the physiological changes which the passive defence response in birds and other animals

Marine animal behaviour: neglecting ocean currents can lead us up the wrong track

Tracks of marine animals in the wild, now increasingly acquired by electronic tagging of individuals, are of prime interest not only to identify habitats and high-risk areas, but also to gain detailed information about the behaviour of these animals. Using recent satellite-derived current estimates and leatherback turtle (Dermochelys coriacea) tracking data, we demonstrate that oceanic currents, usually neglected when analysing tracking data, can substantially distort the observed trajectories. Consequently, this will affect several important results deduced from the analysis of tracking data, such as the evaluation of the orientation skills and the energy budget of animals or the identification of foraging areas. We conclude that currents should be systematically taken into account to ensure the unbiased interpretation of tracking data, which now play a major role in marine conservation biology

Ornamental colors reveal age in the king penguin

We investigated whether delayed plumage maturation occurred in king penguins (Aptenodytes patagonicus). Therefore we examined the relationships between age and sex on spectral properties and size of two colored plumage patches and a UV-reflective beak spot, using known-age cohorts. Unlike the colored patch on the breast, we found age differences in ear and beak coloration. These results suggest that head ornaments in king penguins could signal sexual maturity or social status. No sex differences were found in the intensity of colored ornaments, which can result from mutual mate choice or genetic correlation between sexes. Size of colored patches did not relate to age or sex

Preliminary investigations of prey pursuit and capture by king penguins at sea

Prey pursuit and capture by king penguins (Aptenodytes patagonicus) were investigated with multiple data recorders in the Crozet Archipelago during the 1995/96 austral summer. Birds were fitted with a swim speed and depth data logger that sampled every second making possible fine-scale analyses of underwater behavior. Data were obtained for two birds for periods of 2.5 and 2.9 days, respectively. During each dive deeper than 30m, the swimming speed was constant at around 2m/s, defined as "cruising" speed. However, steep acceleration events ("dashes") were observed. These dashes occurred in "U", "W" and "Plateau" shaped dives. Based on their shape, these dashes were separated into "Rushes" (28% of all dash events) where penguins moved upward and increased their speed from the cruising speed; "Adjusts" (59%) where penguins swam also upward and increased their speed to return to cruising speed after a short slow-down, and "Intermediates" (13%) which were "Adjusts" events that briefly overshot the cruising speed. "Rushes" mainly occurred at the bottom phase of deep dives. They were followed by other dash events in 80% of cases. Moreover, "Rushes" lasted longer and the distance traveled during them was bigger compared to other dash events. "Adjusts" events were observed at the bottom phase and early part of the ascent phase. They were single events within a dive in 50% of cases. These results suggested that dashes, especially "Rushes" may be the main pursuit and capturing behavior performed by king penguins on patchily distributed preys in water deeper than 100m

Intestinal gluconeogenesis and glucose transport according to body fuel availability in rats

Intestinal hexose absorption and gluconeogenesis have been studied in relation to refeeding after two different fasting phases: a long period of protein sparing during which energy expenditure is derived from lipid oxidation (phase II), and a later phase characterized by a rise in plasma corticosterone triggering protein catabolism (phase III). Such a switch in body fuel uses, leading to changes in body reserves and gluconeogenic precursors, could modulate intestinal gluconeogenesis and glucose transport. The gene and protein levels, and the cellular localization of the sodium-glucose cotransporter SGLT1, and of GLUT5 and GLUT2, as well as that of the key gluconeogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (Glc6Pase) were measured. PEPCK and Glc6Pase activities were also determined. In phase III fasted rats, SGLT1 was up-regulated and intestinal glucose uptake rates were higher than in phase II fasted and fed rats. PEPCK and Glc6Pase mRNA, protein levels and activities also increased in phase III. GLUT5 and GLUT2 were down-regulated throughout the fast, but increased after refeeding, with GLUT2 recruited to the apical membrane. The increase in SGLT1 expression during phase III may allow glucose absorption at low concentrations as soon as food is available. Furthermore, an increased epithelial permeability due to fasting may induce a paracellular movement of glucose. In the absence of intestinal GLUT2 during fasting, Glc6Pase could be involved in glucose release to the bloodstream via membrane trafficking. Finally, refeeding triggered GLUT2 and GLUT5 synthesis and apical recruitment of GLUT2, to absorb larger amounts of hexoses