Abstract: Stress exposure and stress response are likely to vary according to life history strategies and environmental contexts. Although the acute release of glucocorticoids in response to unpredictable environmental conditions may lead to adaptative behavioral and physiological responses, exposure to high glucocorticoid levels on the long-term usually leads to deleterious cascading effects on animal’s physiology, behavior and fitness. Yet, some species may be more adapted to cope with challenging events than others and might naturally possess protective mechanisms limiting the adverse consequences of prolonged exposure to high glucocorticoid levels. King penguin chicks being naturally exposed to harsh weather, prolonged fasting and constant predation pressure, we investigated the life-history, behavioral and physiological consequences of an experimental increase in corticosterone levels on the medium and long-term (after removing implants), predicting to find relatively few costs associated with such treatment. Although non-significant, CORT-treated chicks were slightly larger, fledged slightly earlier and had slightly higher survival chances than placebo chicks. CORT-treated chicks were significantly more aggressive and displayed lower corticosterone response to acute stress on the medium term, while their physical activity and whole-body energetics were not significantly affected. While mitochondrial density was not significantly affected by the CORT treatment, CORT-treated chicks had lower oxidative stress levels on the long-term than placebo ones, and no significant impact was observed on telomere shortening. Finally, the expression of several genes (i.e. CORT receptor, HSP90, mTOR, NRF2 and TERF2) was up regulated in treated chicks, which could potentially mediate the apparent ‘stress’ resistance we observed at the phenotypic level.

Abstract: Studies of the effects of variation in resource availability are important for understanding the ecology of high-latitude mammals. This paper examines the potential of dental evidence (tooth wear and breakage) as a proxy for diet and food choice in Vulpes lagopus, the Arctic fox. It presents a preliminary study of dental microwear, gross wear score, and tooth breakage in a sample (n?=?78 individuals) from the Yamal Peninsula of the Russian Arctic. While these measures have each been associated with feeding ecology in larger carnivorans (e.g., proportion of bone in the diet), they have yet to be combined in any study and have rarely been applied to smaller species or those from high latitudes. Arctic foxes from the north and south of the peninsula, and those from rodent peak and trough density periods, are compared to assess impact of changes in food availability across space and time. Results indicate that microwear textures vary in dispersion, with more variation in texture complexity, including higher values (suggesting more consumption of bone), in the rodent-poor period in the north of Yamal. Gross wear scores and tooth breakage are also significantly higher for the north of Yamal than the south. These data together suggest that dental evidence can provide important insights into variation in the feeding ecology of Arctic foxes and potentially into the impacts of changes in food abundance across space and time.

Abstract: Synchrony in ecological systems, the degree to which elements respond similarly over time or space, can inform our understanding of how ecosystems function and how they are responding to global change. While studies of ecological synchrony are often focused on within-species dynamics, synchrony among species may provide important insights into how dynamics of one species are indicative of conditions relevant to the larger community, with both basic and applied implications. Ecological theory suggests there may be conditions under which communities might exhibit increased synchrony, however, the degree to which these patterns are borne out in natural systems is currently unknown. We used long-term breeding success data from a community of Antarctic seabirds to assess the degree of interspecific, community synchrony, and the role that extreme events play in driving these dynamics. We assessed theoretical links between community synchrony, niche separation, and environmental variability using data from this and three other seabird communities as well as a simulation study. Results show that reproductive success for individual species in the Antarctic seabird community fluctuated relatively independently from one another, resulting in little synchrony across this community, outside of extreme years. While an exceptionally poor year for a given species was not necessarily associated with an exceptionally poor year for any other species, one community-wide extreme year existed. When compared to other seabird communities, this group of Antarctic seabirds exhibited lower overall synchrony and higher estimated niche separation, supporting theoretical predictions. Empirical and simulation-derived results suggest that communities where temporal variation is small for conditions in which species respond substantially differently, and large for conditions in which species respond similarly, may exhibit more synchronous dynamics. Identifying where and why synchronous dynamics might be more apparent has the potential to inform how ecological communities might respond to future global change.