Evol Ecol Res 5: 1151-1162 (2003)     Full PDF if your library subscribes.

Energetic savings and the body size distributions of gliding mammals

Roman Dial*

Department of Environmental Science, Alaska Pacific University, 4101 University Drive, Anchorage, AK 99508, USA

e-mail: roman@alaskapacific.edu


Natural selection should favour gliding when it is energetically favourable. I use published allometric relationships to determine an upper limit for body mass in mammalian gliders (flying squirrels, marsupial gliders, colugos and anomalurids). The energetic cost to walk distance D scales as body mass raised to the 2/3 power. To glide distance D using the glide angle θ, a glider must climb to height H, where H = Dtanθ. The energetic cost of climbing to height H scales linearly with body mass. Most published accounts put glide angle at about 25°. I use this angle to compare the energetic costs of walking D metres with climbing H metres to glide D metres. A gliding mammal that weighs 0.4 kg achieves the greatest savings over walking, whereas a 2.5 kg mammal expends the same energy walking as climbing to glide. These masses compare favourably with published body mass distributions of independent glider faunas from Africa (6 species), Borneo (15 species) and Australia (6 species). In each of these three assemblages, the largest glider is ∼2 kg and the mean glider mass is ∼0.5 kg. Gliding mammals may have fairly straightforward constraints on their body size.

Keywords: body size, body size distribution, energetics, mammalian gliders.

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