Stable isotopes are increasingly being used to trace wildlife movements. A fundamental prerequisite of animal isotopic tracking is a good knowledge of spatial isotopic variations in the environment. Few accessible reference maps of the isotopic landscape ("isoscapes") are available for marine predators. Here, we validate for the first time an isotopic gradient for higher trophic levels by using a unique combination of a large number of satellite-tracks and subsequent blood plasma isotopic signatures from a wide-ranging oceanic predator. The plasma δ(13)C and δ(15)N values of wandering albatrosses (n = 45) were highly and positively correlated to the Southern Ocean latitudes at which the satellite-tracked individuals foraged. The well-defined latitudinal baseline carbon isoscapes in the Southern Ocean is thus reflected in the tissue of consumers, but with a positive shift due to the cumulative effect of a slight (13)C-enrichment at each trophic level. The data allowed us to estimate the carbon isotopic position of the main oceanic fronts in the area, and thus to delineate robust isoscapes of the main foraging zones for top predators. The plasma δ(13)C and δ(15)N values were positively and linearly correlated, thus suggesting that latitudinal isoscapes also occur for δ(15)N at the base of the food web in oceanic waters of the Southern Ocean. The combination of device deployments with sampling of relevant tissues for isotopic analysis appears to be a powerful tool for investigating consumers' isoscapes at various spatio-temporal scales.

How does an animal age in natural conditions? Given the multifaceted nature of senescence, identifying the effects of age on physiology and behavior remains challenging. We investigated the effects of age on a broad array of phenotypic traits in a wild, longlived animal, the wandering albatross. We studied foraging behavior using satellite tracking and activity loggers in males and females (age 6-48+ years), and monitored reproductive performance and nine markers of baseline physiology known to reflect senescence in vertebrates (humoral immunity, oxidative stress, antioxidant defenses, and hormone levels). Age strongly affected foraging behavior and reproductive performance, but not baseline physiology. Consistent with results of mammal and human studies, age affected males and females differently. Overall, our findings demonstrate that age, sex, and foraging ability interact in shaping aging patterns in natural conditions. Specifically, we found an unexpected pattern of spatial segregation by age; old males foraged in remote Antarctica waters, whereas young and middle-aged males never foraged south of the Polar Front. Old males traveled a greater distance but were less active at the sea surface, and returned from sea with elevated levels of stress hormone (corticosterone), mirroring a low foraging efficiency. In contrast to findings in captive animals and shortlived birds, and consistent with disposable soma theory, we found no detectable age-related deterioration of baseline physiology in albatrosses. We propose that foraging efficiency (i.e., the ability of individuals to extract energy from their environment) might play a central role in shaping aging patterns in natural conditions. senescence | foraging | immunity | oxidative stress | sex S enescence, a decline in fitness with advancing age, has been documented across a wide range of wild animals (1-3). There is an ongoing debate in the literature regarding the proximate mechanisms underpinning senescence. Age-associated immune dysfunction (referred to as immunosenescence) and increased susceptibility to oxidative stress are strong candidates as the major driving forces behind senescence in humans and laboratory animal models (4-6), but their relevance in natural populations remains unclear. Because of their generally longer lifespan compared with mammals, birds have emerged as predominant models for studying aging (7,8). The first studies on senescence were restricted almost entirely to investigations of age-dependent mortality or breeding performance (1). More recent pioneering studies that focused on proximal physiological patterns of aging in free-living birds yielded contrasting results; senescence was linked with decreased humoral immune response (9), increased oxidative stress (10), altered plasma levels of some hormones (refs. 2, 11; but see ref. 12), and decreased metabolic rate (ref. 13, but see ref. 14).Foraging behavior, the set of processes by which organisms acquire energy and nutrients (15), merits specific attention, because it may play a k...

We made a first descriptive study of weedy sunflowers infesting sunflower crop fields in one Spanish and three French regions. Overall, weedy sunflowers affected around 15% of sunflower fields. Infested fields were most often dispersed over the study areas without evident geographical clustering. In France, five weedy populations were surveyed more intensively. They were composed of a large diversity of morphotypes showing a combination of typical wild and domesticated traits in proportions that differed between populations. Yield losses reached 50% in heavily infested patches. Our results suggest that weedy sunflowers may have arisen through the hybridization of cultivated and wild sunflower, potentially during the seed production process. Such crop-wild hybrids would have been introduced recurrently into fields through the seed lots, where they evolved to locally invasive weedy populations.

Evidence of age-dependent changes in foraging behavior of free-ranging individuals is scarce, especially at older stages. Using the isotopic niche as a proxy of the trophic niche during both the breeding (blood) and inter-nesting (feather) periods, we report here empirical evidence for age-, gender-, and breeding status-dependent foraging ecology and examine its potential consequences on subsequent reproduction and survival in an extremely long-lived species, the Wandering Albatross (Diomedea exulans). Immature Wandering Albatrosses of both sexes forage in the subtropics (delta13C) and feed at the same trophic position (delta15N) as the adults. In contrast to immature birds, adult females forage, on average, at more northern latitudes than males, with both sexes feeding in the subtropics during the internesting period, and males, not females, favoring subantarctic waters during incubation. In contrast to adult females, males show a unique pattern among birds and mammals of a continuous change with age in their main feeding habitat by foraging progressively farther south in colder waters during both the breeding and inter-nesting periods. In males, foraging at higher latitudes (lower feather delta13C values) is associated with a lower probability of breeding during the following years compared to other birds, but with no effect on their probability of surviving. Foraging in cold and windy waters may be linked to foraging impairment that might explain different life history trade-offs and lower investment in reproduction with age. This key point requires further longitudinal investigations and/or studies examining foraging success and the energy budget of birds feeding in different water masses.