THE GENERAL BIOLOGY OF PENGUINS
179
following the expression y x 0 . 3 8 ~ + 0.04 (coefficient of correlation
0.87, 8.e. 0.05).
The genera show interesting relations about the regression line. Fairy
penguins form an isolated group, all of similar length and generally on
the heavy side, with the stockily-built White-flippered penguin farthest
from the mean. Spheniscids are spaced evenly along the line, with the
South American species providing a clear demonstration of Bergmann’s
rule (cf. pygoscelids below). Eudyptids form two distinct groups, with
the smaller temperate species grouped about 3 kg and the larger species
of cooler climates grouped about 4-4.5 kg. Pygoscelids form a series a t
the upper end of the medium-size range; this genus as a whole and
the Gentoos as a tripartite species defy Bergmann’s rule unequivocally. Northern Gentoos are considerably longer, but only slightly
heavier, than their southern counterpart, and those of Macquarie Island
occupy an intermediate position. Addies, Chinstraps and Southern
Gentoos are closely grouped; this is not surprising in three closelyrelated forms which in places form mixed colonies. Their proportions are
nearly matched by those of Magellanic penguins (which they surround
on the graph).
Of the medium-sized penguins living in cold climates only the Royal is
especially heavy for its length; fat used as insulation and food store does
not add notably to mean body weight in animals of this size range.
Stored fat may help to account for the more massive appearance and
beer-bottle proportions, and higher weight-to-length ratio, of Kings and
(more especially) Emperors. Their insulation requirements, proportional
to surface area, are relatively less than those of the smaller species, but
their energy requirements (which are proportional to weight) are probably greater. An Emperor or King penguin in pre-moult fat, immediately
before facing its most serious and rapid energy drain, is barely able to
waddle ashore.
FIG. 10. Body length, plumage length and flipper area in relation to weight.
Key
E
Emperor
MC
Macaroni
SB
Southern Blue
K
King
RL
Royal
NB
Northern Blue
E
Erect-crested
CT
Chatham I.
Y
Yellow-eyed
R
Rockhopper
W
White-flippered
F
Fjordland
A
AdBlie
S
SnaresI.
C
Chinstrap
GN Gentoo, Northern
G
Galapagos
GS
Gentoo, Southern
P
Peruvian
GM
Gentoo, Macquarie
M
Magellmic
B
Blackfooted
179
following the expression y x 0 . 3 8 ~ + 0.04 (coefficient of correlation
0.87, 8.e. 0.05).
The genera show interesting relations about the regression line. Fairy
penguins form an isolated group, all of similar length and generally on
the heavy side, with the stockily-built White-flippered penguin farthest
from the mean. Spheniscids are spaced evenly along the line, with the
South American species providing a clear demonstration of Bergmann’s
rule (cf. pygoscelids below). Eudyptids form two distinct groups, with
the smaller temperate species grouped about 3 kg and the larger species
of cooler climates grouped about 4-4.5 kg. Pygoscelids form a series a t
the upper end of the medium-size range; this genus as a whole and
the Gentoos as a tripartite species defy Bergmann’s rule unequivocally. Northern Gentoos are considerably longer, but only slightly
heavier, than their southern counterpart, and those of Macquarie Island
occupy an intermediate position. Addies, Chinstraps and Southern
Gentoos are closely grouped; this is not surprising in three closelyrelated forms which in places form mixed colonies. Their proportions are
nearly matched by those of Magellanic penguins (which they surround
on the graph).
Of the medium-sized penguins living in cold climates only the Royal is
especially heavy for its length; fat used as insulation and food store does
not add notably to mean body weight in animals of this size range.
Stored fat may help to account for the more massive appearance and
beer-bottle proportions, and higher weight-to-length ratio, of Kings and
(more especially) Emperors. Their insulation requirements, proportional
to surface area, are relatively less than those of the smaller species, but
their energy requirements (which are proportional to weight) are probably greater. An Emperor or King penguin in pre-moult fat, immediately
before facing its most serious and rapid energy drain, is barely able to
waddle ashore.
FIG. 10. Body length, plumage length and flipper area in relation to weight.
Key
E
Emperor
MC
Macaroni
SB
Southern Blue
K
King
RL
Royal
NB
Northern Blue
E
Erect-crested
CT
Chatham I.
Y
Yellow-eyed
R
Rockhopper
W
White-flippered
F
Fjordland
A
AdBlie
S
SnaresI.
C
Chinstrap
GN Gentoo, Northern
G
Galapagos
GS
Gentoo, Southern
P
Peruvian
GM
Gentoo, Macquarie
M
Magellmic
B
Blackfooted