Adaptation of Galápagos Penguins for Life in Two Different Environments

Boersma, Dee

doi:10.1007/978-1-349-02270-0_6

Cited by 23 publications

(9 citation statements)

References 9 publications

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“…Molt in at least some species (penguins) strongly disrupts this air layer (Boersma 1975), so molt might also affect buoyancy. Unlike seals (Kooyman 1989), diving birds apparently maintain gas exchange between blood, lungs, and air sacs to depths of at least 68 m (Kooyman et al 1971(Kooyman et al , 1973.…”

Section: Introductionmentioning

confidence: 99%

Effects of body size, body fat, and change in pressure with depth on buoyancy and costs of diving in ducks (Aythya spp.)

Lovvorn¹,

Jones²

1991

Can. J. Zool.

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LOVVORN, J. R., and JONES, D. R. 1991. Effects of body size, body fat, and change in pressure with depth on buoyancy and costs of diving in ducks (Aythya spp.). Can. J. Zool. 69: 2879-2887. Recent studies of diving ducks (Aythya spp.) have shown that buoyancy is far more important to locomotor costs of shallow diving than is hydrodynamic drag. Working with Canvasbacks (A. valisineria), Redheads (A. americana), and Lesser Scaup (A. aflnis), we investi ated factors affecting buoyancy in models of locomotor energetics. Body volume can be accurately estimated from body mass ( rf = 0.82-0.95), but equations sometimes differ among species, and body volume relative to mass is higher in winter than in summer. Wing molt does not influence body volume or buoyancy. In scaup, an increase in body lipid from 35 to 190 g (from 5.4 to 22.3% of body mass) increases the energy costs of descent more through the inertial effects of higher mass and added mass of entrained water (82.8% of change) than through greater work against drag (12.0%) or buoyancy (5.2%). Costs of foraging at the bottom are 20% lower in the fatter birds because increased inertial resistance to the buoyant force is greater than the increase in buoyancy. Maximal changes in body lipid and associated hypertrophied muscle raise overall costs of diving to a depth of 2 m by only 2%. Such effects can be offset by altering respiratory and plumage air volumes (+I5 mL for a 155-g lipid increase) or the relative amount of time spent at the bottom. Hence, diving energetics contrast with the energetics of flight, which are strongly affected by body mass changes. Reduced buoyancy from compression of air spaces with depth lowers costs of bottom foraging in scaup by 24% at 1.2 m and 36% at 2 m. Mass-specific plumage air volume decreases with increasing body mass (slope = 0.12)' and body tissues are incompressible relative to air. Thus, buoyancy decreases faster with increasing pressure in smaller birds and they become negatively buoyant at shallower depths (about 43 m for Oldsquaws, Clangula hyemalis). Ducks such as eiders (Somateria spp.) weighing over 1200 g and diving to less than 60 m probably never become negatively buoyant. LOVVORN, J. R., et JONES, D. R. 1991. Effects of body size, body fat, and change in pressure with depth on buoyancy and costs of diving in ducks (Aythya spp.). Can. J. Zool. 69 : 2879-2887. Des etudes rkcentes sur les canards plongeurs (Aythya spp.) ont dkmontrk que la flottabilitk contribue beaucoup plus que la trainke hydrodynamique au coQt de la locomotion au cours de la plongke. Nous avons tent6 de dkteminer les facteurs qui affectent la flottabilitk en ktudiant des Morillons h dos blanc (A. valisineria), des Morillons h tCte rouge (A. americana) et des Petits Morillons (A. aflnis) et en intCgrant nos rksultats h des mod&les d'knergie locomotrice. Le volume du corps peut Ctre estimk justement d9apr&s la masse corporelle (2 = 0,82-0,97), mais les equations different parfois selon l'esp&ce et les rapportsvolume/masse sont plus ClevCs en hiver qu'en k...

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Section: Introductionmentioning

confidence: 99%

Effects of body size, body fat, and change in pressure with depth on buoyancy and costs of diving in ducks (Aythya spp.)

Lovvorn¹,

Jones²

1991

Can. J. Zool.

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“…Standing or lying with the flippers extended and exposing the bare facial patches are postures particularly important in regulating the heat budget of Spheniscus penguins under heat stress (e.g. Boersma 1975;Frost et al 1976;Luna-Jorquera 1996). Panting, an extreme mechanism of respiratory evaporative cooling in penguins (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…It is thus likely that penguins rely to a large degree on behaviour for thermoregulation, this being particularly pertinent in Spheniscus penguins which live in temperate and tropical regions (e.g. Galapagos, Peru-Chile, southern Africa) with cold upwelled waters, but hot terrestrial habitats (Boersma 1975;Frost et al 1976;Luna-Jorquera et al 1997). In temperate regions, where seasons are marked, differential behavioural responses during the warm and cold seasons may be expected and, by observation of these , it should be possible to obtain a measure of the thermal milieu experienced by the birds.…”

Section: Introductionmentioning

confidence: 96%

Seasonal variations in the behavioural thermoregulation of roosting Humboldt penguins (Spheniscus humboldti) in north-central Chile

Simeone¹,

Luna‐Jorquera

Wilson³

2004

J Ornithol

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We examined the thermoregulatory behaviour (TRB) of roosting Humboldt penguins (Spheniscus humboldti) in north central Chile during summer and winter, when ambient temperatures (T a ) are most extreme. Each body posture was considered to represent a particular TRB, which was ranked in a sequence that reflected different degrees of thermal load and was assigned an arbitrary thermoregulatory score. During summer, birds exhibited eight different TRBs, mainly oriented to heat dissipation, and experienced a wide range of T a (from 14 to 31°C), occasionally above their thermoneutral zone (TNZ, from 2 to 30°C), this being evident by observations of extreme thermoregulatory responses such as panting. In winter, birds exhibited only three TRBs, mainly oriented to heat retention, and experienced a smaller range of T a (from 11 to 18°C), always within the TNZ, even at night. The components of behavioural responses increased directly with the heat load which explains the broader behavioural repertoire observed in summer. Since penguins are primarily adapted in morphology and physiology to cope with low water temperatures, our results suggest that behavioural thermoregulation may be important in the maintenance of the thermal balance in Humboldt penguins while on land.

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“…This species and the closely related Aptenodytes patagonicus (king penguin) both possess brood pouches that allow them to incubate their eggs and warm their chicks during long periods of subfreezing temperatures. In contrast, Spheniscus mendiculus (Gal apagos penguin) breeds at the Equator and must protect its eggs from the sun to keep them from overheating (Boersma, 1975).…”

mentioning

confidence: 99%

Penguins Past, Present, and Future: Trends in the Evolution of the Sphenisciformes

Ksepka

Ando

2011

Living Dinosaurs

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Adaptation of Galápagos Penguins for Life in Two Different Environments

Cited by 23 publications

References 9 publications

Effects of body size, body fat, and change in pressure with depth on buoyancy and costs of diving in ducks (Aythya spp.)

Effects of body size, body fat, and change in pressure with depth on buoyancy and costs of diving in ducks (Aythya spp.)

Seasonal variations in the behavioural thermoregulation of roosting Humboldt penguins (Spheniscus humboldti) in north-central Chile

Penguins Past, Present, and Future: Trends in the Evolution of the Sphenisciformes

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