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B. STONEROUSE
Flipper and foot measurements are significant in an investigation of
heat balance, as both organs are used to shed excess body heat. The
ventral or upper surface of the feet, and the inner surface of the flipper,
are well vascularized with capillaries which flush with blood in overheated birds (personal observations of five species). In contrast the undersurface of the foot is heavily corneified and thermally inert, and the
dorsal surface of the flipper is only moderately supplied with vessels
(see early anatomical accounts by Watson, 1883; Filhol, 1883, and recent
field investigations by Prevost and Sapin-Jaloustre, 1964). These and
other heat-shedding organs are now being studied comparatively in
species from warm and cold climates.
The feet are used for walking, for steering (but not driving) in water,
for preening, grooming and scratching, and for clearing debris from nest
sites. The long tough claws grip and hold on slippery surfaces, and help
to propel the birds forward in a prone position on mud and snow. The
webs are variable but generally small. Penguins resting upright stand on
the heavily corneified tarsometatarsi and the tail, with toes lifted slightly
from the ground. Flippers are used for swimming, for propulsion in the
prone position over snow, for scrambling on all fours (especially the
smaller species) and in fighting and copulation. Feet and flippers both
increase directly with body length throughout the family, although
relative proportions vary between species (Fig. 11).
The ratio of foot length to body length varies from 15% to 21%, with
a mean of 17%. Emperors have proportionately the smallest feet, actually shorter than Kings’ and effectively less exposed to cold air because
of the long tibiotarsal feathers which fringe and protect the tarsometatarsus. Yellow-eyed penguins have proportionately the longest feet,
with Snares, Fjordland and Fairy penguins following closely. Ratios of
flipper length to body length vary between 24% and 32% (mean 27%).
Correlation between the two ratios is slight, and there is no clear correlation of either with environmental temperature. However, in the three
genera Pygoscelis, Aptenodytes and Eudyptes, the southern representatives (respectively AdBlie, Emperor and Mascaroni) have proportionately
the smallest feet and flippers.
As propelling agents, flippers should vary in length directly in proportion to the diameter of cross section of the body. Of the seven forms for
which I have reliable girth figures, six show a close correlation between
diameter and flipper length (Fig. 12: y = 1 . 6 ~
- 4.2; r = 0.97, s.e. =
0.02). Emperor flippers, only fractionally longer than Kings’, are by this
expression some 9 cm short of their theoretical value.
The efficiency of flippers as facultative radiators should vary in proportion to their area. Mean areas have been determined for each species
and sub-species empirically (Table I and Fig. 10a). Excluding the two
B. STONEROUSE
Flipper and foot measurements are significant in an investigation of
heat balance, as both organs are used to shed excess body heat. The
ventral or upper surface of the feet, and the inner surface of the flipper,
are well vascularized with capillaries which flush with blood in overheated birds (personal observations of five species). In contrast the undersurface of the foot is heavily corneified and thermally inert, and the
dorsal surface of the flipper is only moderately supplied with vessels
(see early anatomical accounts by Watson, 1883; Filhol, 1883, and recent
field investigations by Prevost and Sapin-Jaloustre, 1964). These and
other heat-shedding organs are now being studied comparatively in
species from warm and cold climates.
The feet are used for walking, for steering (but not driving) in water,
for preening, grooming and scratching, and for clearing debris from nest
sites. The long tough claws grip and hold on slippery surfaces, and help
to propel the birds forward in a prone position on mud and snow. The
webs are variable but generally small. Penguins resting upright stand on
the heavily corneified tarsometatarsi and the tail, with toes lifted slightly
from the ground. Flippers are used for swimming, for propulsion in the
prone position over snow, for scrambling on all fours (especially the
smaller species) and in fighting and copulation. Feet and flippers both
increase directly with body length throughout the family, although
relative proportions vary between species (Fig. 11).
The ratio of foot length to body length varies from 15% to 21%, with
a mean of 17%. Emperors have proportionately the smallest feet, actually shorter than Kings’ and effectively less exposed to cold air because
of the long tibiotarsal feathers which fringe and protect the tarsometatarsus. Yellow-eyed penguins have proportionately the longest feet,
with Snares, Fjordland and Fairy penguins following closely. Ratios of
flipper length to body length vary between 24% and 32% (mean 27%).
Correlation between the two ratios is slight, and there is no clear correlation of either with environmental temperature. However, in the three
genera Pygoscelis, Aptenodytes and Eudyptes, the southern representatives (respectively AdBlie, Emperor and Mascaroni) have proportionately
the smallest feet and flippers.
As propelling agents, flippers should vary in length directly in proportion to the diameter of cross section of the body. Of the seven forms for
which I have reliable girth figures, six show a close correlation between
diameter and flipper length (Fig. 12: y = 1 . 6 ~
- 4.2; r = 0.97, s.e. =
0.02). Emperor flippers, only fractionally longer than Kings’, are by this
expression some 9 cm short of their theoretical value.
The efficiency of flippers as facultative radiators should vary in proportion to their area. Mean areas have been determined for each species
and sub-species empirically (Table I and Fig. 10a). Excluding the two