Vincent Lecomte

Patterns of aging in the long-lived wandering albatross

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, long-lived 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 short-lived 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.

Age, sex, and breeding status shape a complex foraging pattern in an extremely long‐lived seabird

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.