ENERGETICS AND ANIMAL PRODUCTIVITY
103
Microtus had a great advantage in being able t o utilize most of the food
it consumed.
c. TROPHIC STUDIES IN A SAVANNAH COMMUNITY
Last to be reviewed in this paper is an energetics study done on the
African Savannah and concerned with the largest land animal, the
African Elephant. Petrides and Swank (1965) studied a population of
Loxdonta africana in 28-5 square miles (7381.5 hectares) of Queen
Elizabeth National Park, Uganda. They count,ed the individuals in the
total population and classified them according to sex and age. Their age
distribution was as follows: 14.6% calves, 24.3% immatures, 14.4%
sub-adults, and 46.7% adults. Growth rate data came from other
sources and were chiefly based on measurements of captive elephants in
zoos. From these data a growth curvg was plotted which fitted the size
of the wild individuals. The authors then created a life table, using
growth rates and population structure. They estimated that 70% of
the calves survived the 1st year. Their survival rate then jumped to
80% in the 2nd year and was 95% by puberty in the 14th year. After
the beginning adult years when the survival rate was 98%, it began to
drop again. An average elephant fixed as new protoplasm 165.6 x los
kcal/year, but since there were only 5-31 elephants per square mile, net
production amounted to only 0.34 kcal/m2/yem.
The physiological data of Benedict (1936) on elephants were used to
calculate maintenance metabolism and rate of ingestion. Petrides and
Swank established that for the elephant an tbverage standing crop of
7.1 kcal on 1 m2 respired 23 kcal and consumed 71.6 kcal of food annually. Gross productivity was 23.34 kcal/m2/yesr, while net productivity
was only 0.34 kcal/m2/year. The elephant used 9.6% of the total browse
available.
Petrides and Swank compared the productivity of the African elephant
to that of the mouse, white-tailed deer, and cattle. They found that the
elephant maintained a tremendous biomass 0x1 a relatively coarse diet.
Assimilation was poor (44%) when compared with that of other mammals, and growth rate was slow; however, net production of the African
elephant was 40% that of good beef cat,tle. The authors also pointed
out that the elephant changed conditions in the Savannah by such activities as digging water holes and pushing down trees, making areas
habitable for other game. The authors went on to suggest how herds
could be managed so as to give maximum benefit to man and other
animals.
The paper by Petrides and Swank is significant in that it demonstrates how physiological data can be applied to field data and good
energetics estimates thereby obtained. The paper also demonstrated
103
Microtus had a great advantage in being able t o utilize most of the food
it consumed.
c. TROPHIC STUDIES IN A SAVANNAH COMMUNITY
Last to be reviewed in this paper is an energetics study done on the
African Savannah and concerned with the largest land animal, the
African Elephant. Petrides and Swank (1965) studied a population of
Loxdonta africana in 28-5 square miles (7381.5 hectares) of Queen
Elizabeth National Park, Uganda. They count,ed the individuals in the
total population and classified them according to sex and age. Their age
distribution was as follows: 14.6% calves, 24.3% immatures, 14.4%
sub-adults, and 46.7% adults. Growth rate data came from other
sources and were chiefly based on measurements of captive elephants in
zoos. From these data a growth curvg was plotted which fitted the size
of the wild individuals. The authors then created a life table, using
growth rates and population structure. They estimated that 70% of
the calves survived the 1st year. Their survival rate then jumped to
80% in the 2nd year and was 95% by puberty in the 14th year. After
the beginning adult years when the survival rate was 98%, it began to
drop again. An average elephant fixed as new protoplasm 165.6 x los
kcal/year, but since there were only 5-31 elephants per square mile, net
production amounted to only 0.34 kcal/m2/yem.
The physiological data of Benedict (1936) on elephants were used to
calculate maintenance metabolism and rate of ingestion. Petrides and
Swank established that for the elephant an tbverage standing crop of
7.1 kcal on 1 m2 respired 23 kcal and consumed 71.6 kcal of food annually. Gross productivity was 23.34 kcal/m2/yesr, while net productivity
was only 0.34 kcal/m2/year. The elephant used 9.6% of the total browse
available.
Petrides and Swank compared the productivity of the African elephant
to that of the mouse, white-tailed deer, and cattle. They found that the
elephant maintained a tremendous biomass 0x1 a relatively coarse diet.
Assimilation was poor (44%) when compared with that of other mammals, and growth rate was slow; however, net production of the African
elephant was 40% that of good beef cat,tle. The authors also pointed
out that the elephant changed conditions in the Savannah by such activities as digging water holes and pushing down trees, making areas
habitable for other game. The authors went on to suggest how herds
could be managed so as to give maximum benefit to man and other
animals.
The paper by Petrides and Swank is significant in that it demonstrates how physiological data can be applied to field data and good
energetics estimates thereby obtained. The paper also demonstrated