No abstract

Foraging skills of young individuals are assumed to be inferior to those of adults. The reduced efficiency of naive individuals may be the primary cause of the high juvenile mortality and explain the deferment of maturity in long-lived species. However, the study of juvenile and immature foraging behaviour has been limited so far. We used satellite telemetry to compare the foraging movements of juveniles, immatures and breeding adult wandering albatrosses Diomedea exulans, a species where foraging success is positively influenced by the distance covered daily. We showed that juveniles are able to use favourable winds as soon as the first month of independence, but cover shorter distances daily and spend more time sitting on water than adults during the first two months after fledging. These reduced movement capacities do not seem to be the cause of higher juvenile mortality. Moreover, juveniles almost never restrict their movement to specific areas, as adults and immatures frequently do over shelf edges or oceanic zones, which suggest that the location of appropriate areas is learned through experience. Immatures and adults have equivalent movement capacities, but when they are central place foragers, i.e. when adults breed or immatures come to the colony to display and pair, immatures make shorter trips than adults. The long duration of immaturity in this species seems to be related to a long period of learning to integrate the foraging constraints associated with reproduction and central place foraging. Our results indicate that foraging behaviour of young albatrosses is partly innate and partly learned progressively over immaturity. The first months of learning appear critical in terms of survival, whereas the long period of immaturity is necessary for young birds to attain the skills necessary for efficient breeding without fitness costs.

No abstract

Home ranges (HRs) are a remarkably common form of animal space use, but we still lack an integrated view of the individual-level processes that can lead to their emergence and maintenance, particularly when individuals are in competition for resources. We built a spatially explicit mechanistic movement model to investigate how simple memory-based foraging rules may enable animals to establish HRs and to what extent this increases their foraging efficiency compared to individuals that do not base foraging decisions on memory. We showed that these simple rules enable individuals to perform better than individuals using the most efficient strategy that does not rely on memory and drive them to spatially segregate through avoidance of resource patches used by others. This striking result questions the common assumption that low HR overlaps are indicators of territorial behavior. Indeed, it appears that, by using an information-updating system, individuals can keep their environment relatively predictable without paying the cost of defending an exclusive space. However, memory-based foraging strategies leading to HR emergence seem unable to prevent the disruptive effects of the arrival of new individuals. This calls for further research on the mechanisms that can stabilize HR spatial organization in the long term.