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First published online August 9, 2007
Journal of Experimental Biology 210, 2851-2858 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.001230

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Differences in metabolic costs of terrestrial mobility in two closely related species of albatross

Alexander P. Kabat^1,*, Richard A. Phillips², John P. Croxall^2, and Patrick J. Butler¹

¹ Centre for Ornithology, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
² British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK

View larger version (6K): [in this window] [in a new window]   Fig. 1. (A) Top view of nest, showing the positions (0, 90, 180, 270°) at the bottom of the nest from which each measurement of slope angle () was taken. (B) Side view of the nests showing the positions from which each measurement of slope is taken where 0° is the nest facing directly down slope, 180° is the nest facing directly up slope, 90° and 270° are taken along the sides of the nest. Slope angle was measured from to the ground to the horizontal plane (dotted lines). (C) Front view schematic of same nest measurements.

View larger version (4K): [in this window] [in a new window]   Fig. 2. Minimum approach angle (; t-test: t=16.7428, P=0.015)) and nest angle (; t-test; t=2.8339, P<0.000) in degrees from horizontal of the ground surrounding the nest (see Fig. 1). Values are means ± s.e.m. for 11 black-browed albatrosses (BBA; open columns) and 5 grey-headed albatrosses (GHA; filled columns).

View larger version (7K): [in this window] [in a new window]   Fig. 3. (A) Mean (± s.e.m.) maximal speeds (km h–1) achieved by 11 black-browed albatross (BBA; open columns) and 5 grey-headed albatross (GHA; filled columns), when walking on the treadmill with a 0% incline. (B) The mean maximal percent incline achieved by GHA and BBA, when walking on the treadmill at a speed of 0.6 km h–1.

View larger version (3K): [in this window] [in a new window]   Fig. 4. Leg length (mean ± s.e.m.) of the 11 black-browed albatross (BBA) and 5 grey-headed albatross (GHA). There is a significant difference between the species (P=0.004).

View larger version (6K): [in this window] [in a new window]   Fig. 5. (A) Stride length (Ls) (mean ± s.e.m.) achieved by five grey-headed albatross (GHA) and 11 black-browed albatross (BBA), when walking on the treadmill at maximal speed with 0% incline (P=0.497). (B) Mean (± s.e.m.) Ls, when walking on the treadmill at a speed of 0.6 km h–1 at maximal % incline. Significant differences can be seen between species (P=0.000). There is also a significant difference (P=0.003) in both BBA and GHA between Ls when performing on the flat (A) and on the incline (B).

View larger version (8K): [in this window] [in a new window]   Fig. 6. Rate of oxygen consumption (O2 in ml min–1) for all the exercise trials (mean ± s.e.m.) conducted on 11 black-browed albatross (BBA) and 5 grey-headed albatross (GHA): (A) non-significant difference in between birds standing on the treadmill without any movement; (B) at cruising speed of 0.6 km h–1 at 0% incline; (C) at maximum speed reached by each species; (D) at maximum incline reached by each species.

View larger version (21K): [in this window] [in a new window]   Fig. 7. (A) Rate of oxygen consumption (O2, ml min–1) achieved by the grey-headed (open circles, N=5) and black-browed albatross (filled diamonds, N=11), when walking on the treadmill at 0.6 km h–1 at varying % inclines. (B) Rate of oxygen consumption achieved by the grey-headed albatross and black-browed albatross when walking on the treadmill at varying speeds. (C) Rate of force generation (1/tc) achieved by the grey-headed albatross and black-browed albatross when walking on the treadmill at 0.6 km h–1 at varying % inclines. (D) 1/tc achieved by the grey-headed albatross and black-browed albatross when walking on the treadmill at varying speeds.

View larger version (4K): [in this window] [in a new window]   Fig. 8. Net vertical efficiency (mean ± s.e.m.) for 5 grey-headed albatross (GHA, open circles and solid line) and 11 black-browed albatross (BBA, filled diamonds and broken line), when walking on the treadmill with at different percent inclines ranging between 2–12%). Regression equation for GHA: y=–3.29x+44.04, R2=0.84, and for BBA: y=–0.69x+22.65, R2=0.35. The GHA data point at 9% represents only one animal; the others were unable to perform at this level.