High-resolution recording of foraging behaviour over multiple annual cycles shows decline in old Adélie penguins' performance

Abstract

Age-related variation in foraging performance can result from both within-individual change and selection processes. These mechanisms can only be disentangled by using logistically challenging long-term, longitudinal studies. Coupling a long-term demographic data set with high-temporal-resolution tracking of 18 Adélie penguins ( Pygoscelis adeliae , age 4–15 yrs old) over three consecutive annual cycles, we examined how foraging behaviour changed within individuals of different age classes. Evidence indicated within-individual improvement in young and middle-age classes, but a significant decrease in foraging dive frequency within old individuals, associated with a decrease in the dive descent rate. Decreases in foraging performance occurred at a later age (from 12–15 yrs old to 15–18 yrs old) than the onset of senescence predicted for this species (9–11 yrs old). Foraging dive frequency was most affected by the interaction between breeding status and annual life-cycle periods, with frequency being highest during returning migration and breeding season and was highest overall for successful breeders during the chick-rearing period. Females performed more foraging dives per hour than males. This longitudinal, full annual cycle study allowed us to shed light on the changes in foraging performance occurring among individuals of different age classes and highlighted the complex interactions among drivers of individual foraging behaviour.

Going with the floe: Sea‐ice movement affects distance and destination during Adélie penguin winter movements

“…For example, Arctic terns have been found to rely more on wind support to travel north but prioritize locating high-productivity areas to refuel during southward movements when facing more headwinds (Hrom adkov a et al, 2020). Our study species may employ a similar strategy, with increased diving/foraging activity ramping up in July and increasing throughout their return to the breeding colony, also coinciding with the need to build energy reserves for fasting during territory establishment, laying and incubation (Lescroël et al, 2023). Overall, our results broadly align with those found for other migrating (flying) seabirds where breeding colony size, competition, individual characteristics, and local habitat conditions all play a role in shaping migratory routes and behaviors (Campioni et al, 2020;Fayet et al, 2017).…”

Age effects on Nazca booby foraging performance are largely constant across variation in the marine environment: Results from a 5‐year study in Galápagos

“…Although naïve seabirds improve in foraging efficiency (Fayet et al, 2015) and body condition (Weimerskirch, 1992) during an extended sub‐adult phase, recruiting to the breeding population poses new challenges. Accordingly, young and/or inexperienced parents are less efficient foragers (Daunt et al, 2007; Galbraith et al, 1999), showing deficits in prey delivery (Limmer & Becker, 2009; Navarro et al, 2010), trip duration (Frankish et al, 2020), and diving (Cunningham et al, 2017; Le Vaillant et al, 2013; Lescroël et al, 2023). Nazca boobies show only weak evidence of reduced foraging performance early in their breeding years, suggesting that recruitment in this species demands a high level of foraging competence (particularly for males) and implicates other factors (e.g., poor coordination between pair members, a lack of breeding experience, and/or deferred investment toward reproduction) in the poor breeding success of young boobies (Forslund & Pärt, 1995; Patrick et al, 2020).…”

“…We used high‐quality GPS data spanning 5 years to address the prediction that an individual's age conditions its foraging performance under environmental variation. Early‐life improvements in foraging ability are well documented in seabirds (e.g., Daunt et al, 2007; Frankish et al, 2020; Galbraith et al, 1999; Lescroël et al, 2019, 2023; Limmer & Becker, 2009) but evidence of physiological senescence degrading late‐life foraging performance has been mixed (observed in Catry et al, 2006, Frankish et al, 2020, Galbraith et al, 1999, but not in Elliott et al, 2015, Froy et al, 2015, Lescroël et al, 2019). Senescence in foraging ability may be revealed only under a challenging environment, a pattern observed for Mass Gain/hour in female Nazca boobies.…”

“…However, despite its central role in an animal's life, age‐related changes in the ability of an organism to meet its energy needs are poorly understood, particularly in late life. In studies done on seabirds, individual foraging ability shows age‐related variation in some cases (e.g., Breed et al, 2011; Frankish et al, 2020; Galbraith et al, 1999; Lescroël et al, 2023; Rutz et al, 2006), but not all (Elliott et al, 2015; Froy et al, 2015), providing an unclear picture of the roles of accumulating experience and other benefits of age versus that of advancing physiological decline for foragers.…”

“…But recruitment to the breeding population poses further challenges. In early life, foraging performance (such as foraging trip duration and the amount of food delivered to nestlings) generally improves with age and experience (e.g., Daunt et al, 2007; Frankish et al, 2020; Galbraith et al, 1999; Lescroël et al, 2019, 2023; Limmer & Becker, 2009). Early‐life improvements in foraging ability may result from increasing experience (e.g., Daunt et al, 2007) or from increasing physiological competence with age (e.g., stronger bite force in middle‐aged versus young female Nazca boobies; Rebol & Anderson, 2022).…”