Intraspecific scaling of flight power in the bat Glossophaga soricina (Phyllostomidae)
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Ó Springer-Verlag 2000
ORIGINAL PAPER
C. C. Voigt
Intraspeci®c scaling of ¯ight power in the bat Glossophaga soricina (Phyllostomidae)
Accepted: 11 May 2000
Abstract Aerodynamic theory predicts that power output during ¯ight should vary with body mass by an exponent of 1.56 when wing morphology remains constant (within an individual), and by an exponent of 1.19 when wing morphology changes with body mass (within a species or between species). I tested these predictions by estimating the power input during horizontal ¯ight in three pregnant and two subadult Glossophaga soricina using a multivariate regression model. This analysis yielded power input during resting and ¯ight as well as the energetic equivalent of change in body mass. A comparison of the estimated ¯ight power for pregnant G. soricina, with published data on ¯ight power of nonpregnant adults, revealed that energy turnover in ¯ight is highest for pregnant G. soricina. Flight power of a 13-g pregnant G. soricina was even higher than that of a 16-g non-pregnant Glossophaga longirostris. A least-squares regression analysis yielded the following equations for the intraspeci®c scaling of ¯ight power with body mass: power input during horizontal ¯ight (Pf) 24099 body mass (bm; kg)2.15 (r2 0.97) for the intra-individual allometry (pregnancy) and Pf 113 bm(kg)0.95 (r2 0.99) for the inter-individual allometry (ontogeny). Both mass exponents are not signi®cantly dierent from the predicted values for the scaling relationship of ¯ight power within an individual (1.56) and within a species (1.19). This is the ®rst measurement of power input during ¯ight for subadult and pregnant bats.
Communicated by G. Heldmaier C. C. Voigt Institut fuÈr Zoologie II, UniversitaÈt Erlangen-NuÈrnberg, Staudtstrasse 5, 91058 Erlangen, Germany Present address: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA e-mail: [email protected]
Key words Flight á Allometry á Glossophaga á Bats á Pregnancy Abbreviations AR aspect ratio á B wing span á bm body mass á BMR basal metabolic rate á DEE daily energy expenditure á DEI daily energy intake á eDbm caloric equivalent of body mass changes á g gravitational force á Pr power input during resting á Pf power input during horizontal ¯ight á Ph power input during hovering ¯ight á DR mobilized or stored reserves á S wing area á tf daily ¯ight duration á tr daily resting duration á WL wing loading
Introduction In modern vertebrates active ¯ight is restricted to birds and bats. Although both taxa encountered the same physical constraints for generating uplift and forward force, some adaptations are remarkably dierent. The wing area of bats, for example, is large compared to similar-sized birds (Norberg and Rayner 1987) which could result in dierent metabolic requirements for ¯ight. Voigt and Winter (1999) showed that power input during hovering ¯ight (Ph) is 40% less in nectar-feeding bats compared to hummingbirds of the same size. By comparing available data of ¯ight costs in
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