Apparent changes in body insulation of juvenile king penguins suggest an energetic challenge during their early life at sea

Abstract

Little is known about the early life at sea of marine top predators, like deep-diving king penguins (Aptenodytes patagonicus), although this dispersal phase is probably a critical phase in their life. Apart from finding favourable foraging sites, they have to develop effective prey search patterns as well as physiological capacities that enable them to capture sufficient prey to meet their energetic needs. To investigate the ontogeny of their thermoregulatory responses at sea, we implanted 30 juvenile king penguins and 8 adult breeders with a small data logger that recorded pressure and subcutaneous temperature continuously for up to 2.5 years. We found important changes in the development of peripheral temperature patterns of foraging juvenile king penguins throughout their first year at sea. Peripheral temperature during foraging bouts fell to increasingly lower levels during the first 6 months at sea, after which it stabilized. Most importantly, these changes re-occurred during their second year at sea, after birds had fasted for ∼4 weeks on land during their second moult. Furthermore, similar peripheral temperature patterns were also present in adult birds during foraging trips throughout their breeding cycle. We suggest that rather than being a simple consequence of concurrent changes in dive effort or an indication of a physiological maturation process, these seasonal temperature changes mainly reflect differences in thermal insulation. Heat loss estimates for juveniles at sea were initially high but declined to approximately half after ∼6 months at sea, suggesting that juvenile king penguins face a strong energetic challenge during their early oceanic existence.

Climate change and functional traits affect population dynamics of a long‐lived seabird

“…There is increasing evidence that during the first year at sea, juvenile seabirds experience a high mortality (Fay et al., ; Oro et al., ), as documented in other taxa (Baron, Le Galliard, Tully, & Ferrière, ; Gaillard et al., ; Ozgul, Armitage, Blumstein, & Oli, ). Due to their inexperience and potentially incomplete growth, young individuals may exhibit lower foraging efficiency relative to that of adults (Enstipp et al., ; Orgeret, Weimerskirch, & Bost, ). Indeed, in other seabirds, the development of tracking technology has revealed lower performance of young individual in flying and diver activity during foraging or migration trips (Harel, Horvitz, & Nathan, ; Orgeret et al., ; Rotics et al., ).…”

Why implantation of bio‐loggers may improve our understanding of how animals cope within their natural environment

“…This latter aspect is especially relevant for studies concerning implanted devices, as they remain inside the animal until retrieved surgically or until its death. Hence, if the implanted animal can be identified (through permanent external marks or internal RFID [radio-frequency identification] tags; Gendner et al 1992;Handrich et al 1995;Gendner et al 2005), device retrieval might be possible for many years following the original implantation, enabling long-term recordings (Enstipp et al 2017). Such recordings are likely to provide new insight into behavioral and physiological patterns, resulting from seasonal and annual changes experienced by the animals.…”

“…During the early 2000s implantable data-loggers allowed the first recordings of behavioral/physiological parameters in seabirds that spanned their annual cycle (Guillemette et al 2002;Green et al 2005aGreen et al ,b, 2009Grémillet et al 2005a,b;White et al 2011;Guillemette & Butler 2012). More recently, implantable data-loggers have been deployed with juvenile king penguins, documenting the behavioral and physiological changes occurring during their first 2.5 years at sea (Enstipp et al 2017).…”

“…How recording duration might affect conclusions reached and provide novel insights is illustrated by the study by Enstipp et al (2017) concerning juvenile king 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 penguins. Enstipp et al subcutaneously implanted data-loggers into juvenile king penguins before their first departure to sea and used an RFID system to retrieve implanted data-loggers (recording for up to 2.5 years) up to 3.5 years after original implantation.…”

“…3), and was also present in adult birds, after each fasting period on land. Hence, this suggested that rather than being indicative of a physiological maturation process, these seasonal temperature changes mainly reflect differences in thermal insulation due to changes in body condition (Enstipp et al 2017). Clearly, extending data recording over multiple years allows investigation of changes in the behavior and physiology of animals in relation to numerous aspects (e.g.…”