ENERGY IN ANIMAL ECOLOGY
97
relative permanence of the spring contours, taken in conjunction with
the leaf fall would indicate that the values measured are not merely
transient stages of a rapid successional process.
Odum and Smalley (1959) have presented a brief summary of Smalley’s doctoral disseration on the energetics of a grasshopper (Orchelimum
Jidicinium) and a snail (Littorina irrorata) on a Georgia Spartina salt
marsh. Assimilation was estimated from the sum of the calorific
equivalents of respiration and total growth which had occurred in the
populations during the study period. Respiration was determined in
the laboratory.
The role of predators in mortality was not evaluated for either the
snail or grasshopper. Year class phenomena seem t o occur in the snail;
indicating a strong possibility that the steady state condition was not
met. Assuming the estimated total growth increment t o be yield, in
some sense and taking estimated food energy assimilated as the denominator, the ecological efficiency of the snail is 14% and of the
grasshopper 37%. If food ingested is taken as denominator the efficiencies are 6% for the snail and 13% for the grasshopper.
Odum and Smalley note that grasshoppers feed on Spartina and
grow rapidly, while the snails feed on detritus and grow slowly. The
total energy assimilated by the snails is only about twice that assimilated by the grasshoppers although the summer average standing
crops were 700 snails/m2 and 10-20 grasshoppers/m2.
H. T. Odum (1957) in a long paper analysing the energetics of a
warm constant-temperature spring (Silver Springs, Florida) has found
the order of magnitude of ecological efficiency to be from 5 t o 16%.
Odum’s detailed theoretical analysis is too complex for adequate
discussion here, but his conclusions are in general agreement with
those of other workers.
Englemann (1961) has combined laboratory and field studies in an
analysis of arthropod microfauna energetics in a Michigan oil field,
with emphasis on the Oribatid mites.
Feeding experiments were conducted in the laboratory, using fungi
and yeast as food. Respiratory rates and growth rates were measured
directly. Bomb calorimetry was used t o determine energy equivalents
of the mites’ food.
He constructed the following energy budget for the oribatid mites
in a square metre of old field.
Ingested
Faeces Egg mortality Adult mortality Respiration
10.25 kcal
7-69
0.16
0-27
1.97
All of these estimates were independent, of each other in the sense
that none were determined by difference. It is, therefore, very remarkD
E.R.-I
97
relative permanence of the spring contours, taken in conjunction with
the leaf fall would indicate that the values measured are not merely
transient stages of a rapid successional process.
Odum and Smalley (1959) have presented a brief summary of Smalley’s doctoral disseration on the energetics of a grasshopper (Orchelimum
Jidicinium) and a snail (Littorina irrorata) on a Georgia Spartina salt
marsh. Assimilation was estimated from the sum of the calorific
equivalents of respiration and total growth which had occurred in the
populations during the study period. Respiration was determined in
the laboratory.
The role of predators in mortality was not evaluated for either the
snail or grasshopper. Year class phenomena seem t o occur in the snail;
indicating a strong possibility that the steady state condition was not
met. Assuming the estimated total growth increment t o be yield, in
some sense and taking estimated food energy assimilated as the denominator, the ecological efficiency of the snail is 14% and of the
grasshopper 37%. If food ingested is taken as denominator the efficiencies are 6% for the snail and 13% for the grasshopper.
Odum and Smalley note that grasshoppers feed on Spartina and
grow rapidly, while the snails feed on detritus and grow slowly. The
total energy assimilated by the snails is only about twice that assimilated by the grasshoppers although the summer average standing
crops were 700 snails/m2 and 10-20 grasshoppers/m2.
H. T. Odum (1957) in a long paper analysing the energetics of a
warm constant-temperature spring (Silver Springs, Florida) has found
the order of magnitude of ecological efficiency to be from 5 t o 16%.
Odum’s detailed theoretical analysis is too complex for adequate
discussion here, but his conclusions are in general agreement with
those of other workers.
Englemann (1961) has combined laboratory and field studies in an
analysis of arthropod microfauna energetics in a Michigan oil field,
with emphasis on the Oribatid mites.
Feeding experiments were conducted in the laboratory, using fungi
and yeast as food. Respiratory rates and growth rates were measured
directly. Bomb calorimetry was used t o determine energy equivalents
of the mites’ food.
He constructed the following energy budget for the oribatid mites
in a square metre of old field.
Ingested
Faeces Egg mortality Adult mortality Respiration
10.25 kcal
7-69
0.16
0-27
1.97
All of these estimates were independent, of each other in the sense
that none were determined by difference. It is, therefore, very remarkD
E.R.-I