Effects of age and reproductive status on individual foraging site fidelity in a long-lived marine predator

Abstract

Individual foraging specializations, where individuals use a small component of the population niche width, are widespread in nature with important ecological and evolutionary implications. In long-lived animals, foraging ability develops with age, but we know little about the ontogeny of individuality in foraging. Here we use precision global positioning system (GPS) loggers to examine how individual foraging site fidelity (IFSF), a common component of foraging specialization, varies between breeders, failed breeders and immatures in a long-lived marine predatorthe northern gannet Morus bassanus. Breeders (aged 5þ) showed strong IFSF: they had similar routes and were faithful to distal points during successive trips. However, centrally placed immatures (aged 2-3) were far more exploratory and lacked route or foraging site fidelity. Failed breeders were intermediate: some with strong fidelity, others being more exploratory. Individual foraging specializations were previously thought to arise as a function of heritable phenotypic differences or via social transmission. Our results instead suggest a third alternative-in long-lived species foraging sites are learned during exploratory behaviours early in life, which become canalized with age and experience, and refined where possiblethe exploration-refinement foraging hypothesis. We speculate similar patterns may be present in other long-lived species and moreover that long periods of immaturity may be a consequence of such memory-based individual foraging strategies.

Inter‐population variation in the behaviour of adult and juvenile Red‐footed Boobies Sula sula

“…In Northern Gannets, immatures show a larger foraging distribution than adults and a smaller individual foraging site fidelity linked to oceanographic fronts that offer better foraging conditions (Votier et al . , Grecian et al . ).…”

“…In Northern Gannets Morus bassanus , individuals can optimize their foraging trips with age (Votier et al . , Grecian et al . ), indicating that the experience of the individual is an important intrinsic determinant of the foraging behaviour.…”

Ecological opportunity drives individual dietary specialization in leopards

“…dependent offspring observing their mothers hunt; Estes et al, ), or there might be a genetic basis to diet variation (Dochtermann, Schwab, & Sih, ). To date, little research has focused on the ontogeny of individual specialization (but see Votier et al, ) and it warrants further attention.…”

“…Optimal foraging theory predicts that both phenotypic constraints and environmental conditions influence the degree of dietary specialization exhibited by individuals (Stephens & Krebs, ). Phenotypic constraints include traits that affect an individual's ability to access and utilize specific food items, for example, sex‐ or age‐related differences in the size, experience and dominance of consumers (Kernaléguen, Cherel, Knox, Baylis, & Arnould, ; Thiemann, Iverson, Stirling, & Obbard, ; Votier et al, ). Environmental conditions, in contrast, relate to ecological factors that affect the amount and types of food available to individuals.…”

“…As such, male leopards should have access to a wider diversity of prey than females, leading to higher levels of specialization (Kernaléguen et al, ; Thiemann et al, ). Adults may also be more specialized than subadults, due to their larger size and greater experience (Votier et al, ). Leopards are strongly territorial (Bailey, ) and, at least in heterogeneous landscapes, the resources available to individuals will likely vary.…”