ENERGETICS A N D ANIMAL PRO DUCTIVITY
83
defined as follows: the efficiency of digestion ia equal to the number of
calories assimilated divided by the number of calories ingested. This
ratio is important because food consumption in the field is difficult to
measure directly. If the investigator has information on either the
amount of ingested material or the growth plus the maintenance
amounts, then the formula for digestive efficiency can give him some
estimate of the food ingested during the period of time in question.
The second ratio of importance to energetics studies is the relationship
between metabolic rate and weight of the animal. This is used also as a
predictive tool in an effort to estimate respiratory rate or metabolic
rate when only the weight of the animal is known. The general formula
for this relationship is: M = aWb, where i t 1 represents metabolic rate,
W is the weight of the individual, and a and b are constants. The value
obtained for the constant b in a set of experiments can be used to compare the metabolism of two animals. Theoretically, a and b should be
constant, and b should be equal to 0.67. However, this is not actually
the case, and the formula for the weight mei;abolism relationship becomes a comparative as well as a predictive tool.
The third ratio is one characteristic of the .Lindeman or trophic efficiency model. When this ratio was first proposed by Lindeman (1942)
he called it “progressive efficiency” and defined it as A, divided by
An-l times 100, where A, was the number of calories ingested by the
organisms feeding on An-l, and An-l is the number of calories ingested
by An-l. Hutchinson (Lindeman 1942) called this the “true productivity’’
of the energy level. Slobodkin (1960) recognizing the confusion surrounding this important ratio renamed it “eco!’ogical efficiency”. Patten
(1959) in his paper on cybernetics and energetics renamed this same
ratio the “efficiency of transfer of ingested energy”; Davis and Golley
(1963) called it “utilization efficiency”; while Wiegert (1964) pleading
for uniformity in nomenclature and for names which outline the important features of the efficiency ratios, introduced the title of “gross
efficiency of yield divided by ingestion”. The term “ecological efficiency” seems to me to be the most convenient and the least ambiguous
and I shall use it when discussing the ratio of the number of calories
removed by the predators (A, ) divided by the number of calories ingested by the prey (An-l) times 100. Note that the ecological efficiency
does not compare gross productivity of two successive levels, but rather
compares the ingestion rates of the two successive levels. Ecological
efficiency, then, is an important ratio when one community is compared
with another, as well as when two trophic levels are compared. The
ratio is primarily important to the Lindeman model rather than to any
practical applications by man. There are other comparisons in the form
of efficiency ratios, made by the trophic analysis, Patten (1959). It may
83
defined as follows: the efficiency of digestion ia equal to the number of
calories assimilated divided by the number of calories ingested. This
ratio is important because food consumption in the field is difficult to
measure directly. If the investigator has information on either the
amount of ingested material or the growth plus the maintenance
amounts, then the formula for digestive efficiency can give him some
estimate of the food ingested during the period of time in question.
The second ratio of importance to energetics studies is the relationship
between metabolic rate and weight of the animal. This is used also as a
predictive tool in an effort to estimate respiratory rate or metabolic
rate when only the weight of the animal is known. The general formula
for this relationship is: M = aWb, where i t 1 represents metabolic rate,
W is the weight of the individual, and a and b are constants. The value
obtained for the constant b in a set of experiments can be used to compare the metabolism of two animals. Theoretically, a and b should be
constant, and b should be equal to 0.67. However, this is not actually
the case, and the formula for the weight mei;abolism relationship becomes a comparative as well as a predictive tool.
The third ratio is one characteristic of the .Lindeman or trophic efficiency model. When this ratio was first proposed by Lindeman (1942)
he called it “progressive efficiency” and defined it as A, divided by
An-l times 100, where A, was the number of calories ingested by the
organisms feeding on An-l, and An-l is the number of calories ingested
by An-l. Hutchinson (Lindeman 1942) called this the “true productivity’’
of the energy level. Slobodkin (1960) recognizing the confusion surrounding this important ratio renamed it “eco!’ogical efficiency”. Patten
(1959) in his paper on cybernetics and energetics renamed this same
ratio the “efficiency of transfer of ingested energy”; Davis and Golley
(1963) called it “utilization efficiency”; while Wiegert (1964) pleading
for uniformity in nomenclature and for names which outline the important features of the efficiency ratios, introduced the title of “gross
efficiency of yield divided by ingestion”. The term “ecological efficiency” seems to me to be the most convenient and the least ambiguous
and I shall use it when discussing the ratio of the number of calories
removed by the predators (A, ) divided by the number of calories ingested by the prey (An-l) times 100. Note that the ecological efficiency
does not compare gross productivity of two successive levels, but rather
compares the ingestion rates of the two successive levels. Ecological
efficiency, then, is an important ratio when one community is compared
with another, as well as when two trophic levels are compared. The
ratio is primarily important to the Lindeman model rather than to any
practical applications by man. There are other comparisons in the form
of efficiency ratios, made by the trophic analysis, Patten (1959). It may