Energy in Animal Ecology
L. B. S L O B O D K I N
Department of Zoology,
University of Michigan, Ann Arbor, Michigan, U.S.A.
I. The Relevance of Energy Studies to Ecology ............................. .G9
11. TheoryofEnergy Budgets .............................................. 73
111. Entropy and Information i n Ecology ................................... . 7 8
IV. Lindeman’s Theoretical Formulation ................................... .82
V. DaphniaEnergetics .................................................... 85
VI. Field Estimates of Efficiency ........................................... .94
VII.Conclusions .......................................................... 99
Acknowledgement ........................................................ 99
References ................................................................ 99
I. THE RELEVANCE OF ENERGY STUDIES TO ECOLOGY
No single measurement is intrinsically significant. All measurements
derive their interest from their context and the richness of predictive
generalizations that can be produced from them. The fact that energy
measurements have high intellectual prestige in chemistry and physics
does not necessarily imply major ecological significance, any more than
electron spin measurements as such have ecological significance.
Precise measurement of energetic parameters is almost impossible,
and even rather crude measurements are time-consuming and expensive.
It must, therefore, be initially established that such measurements are
of sufficient ecological significance t o be worth our trouble.
One demonstration of the relevance and interest of energetics t o
ecology has been presented by Hairston et al. (1960). Energy-rich
organic sediments accumulate at a rate that is completely insignificant
compared with the rate of energy fixation by green plants. This implies
that the biosphere as a whole is energy limited, although individual
decomposer populations may be temporarily limited by predators or
other factors.
In some situations, particularly the free water of lakes and oceans,
plants are depleted by herbivores so that the herbivores are obviously
limited by energy. Occasionally, it can be directly demonstrated that
herbivore population-size is dependent on the rate of energy fixation
by food plants (Borecky, 1956). In terrestrial situations, living vege69
L. B. S L O B O D K I N
Department of Zoology,
University of Michigan, Ann Arbor, Michigan, U.S.A.
I. The Relevance of Energy Studies to Ecology ............................. .G9
11. TheoryofEnergy Budgets .............................................. 73
111. Entropy and Information i n Ecology ................................... . 7 8
IV. Lindeman’s Theoretical Formulation ................................... .82
V. DaphniaEnergetics .................................................... 85
VI. Field Estimates of Efficiency ........................................... .94
VII.Conclusions .......................................................... 99
Acknowledgement ........................................................ 99
References ................................................................ 99
I. THE RELEVANCE OF ENERGY STUDIES TO ECOLOGY
No single measurement is intrinsically significant. All measurements
derive their interest from their context and the richness of predictive
generalizations that can be produced from them. The fact that energy
measurements have high intellectual prestige in chemistry and physics
does not necessarily imply major ecological significance, any more than
electron spin measurements as such have ecological significance.
Precise measurement of energetic parameters is almost impossible,
and even rather crude measurements are time-consuming and expensive.
It must, therefore, be initially established that such measurements are
of sufficient ecological significance t o be worth our trouble.
One demonstration of the relevance and interest of energetics t o
ecology has been presented by Hairston et al. (1960). Energy-rich
organic sediments accumulate at a rate that is completely insignificant
compared with the rate of energy fixation by green plants. This implies
that the biosphere as a whole is energy limited, although individual
decomposer populations may be temporarily limited by predators or
other factors.
In some situations, particularly the free water of lakes and oceans,
plants are depleted by herbivores so that the herbivores are obviously
limited by energy. Occasionally, it can be directly demonstrated that
herbivore population-size is dependent on the rate of energy fixation
by food plants (Borecky, 1956). In terrestrial situations, living vege69