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Metabolic consequences of hard work.
1Department of Animal Ecology, University of Lund, Sweden. jan-ake.nilsson@zooekol.lu.se
Proceedings. Biological Sciences
|September 3, 2002
Summary
Animals meeting increased demands, like parental care, may reallocate energy or increase food intake. Marsh tits showed increased basal metabolic rate with higher feeding rates, supporting the increased-intake strategy for meeting energy demands.
Area of Science:
- Animal Ecology
- Physiological Ecology
- Behavioral Ecology
Background:
- Animals face increased energy demands for tasks like thermoregulation and parental care.
- Two strategies exist: energy reallocation from maintenance (compensation hypothesis) or increased energy intake via larger digestive tracts (increased-intake hypothesis).
Purpose of the Study:
- To investigate the energetic strategies marsh tits (Parus palustris) employ to meet increased parental care demands.
- To test the predictions of the compensation and increased-intake hypotheses.
Main Methods:
- Experimental manipulation of brood size in marsh tits to alter parental effort.
- Measurement of parental feeding rates and basal metabolic rate (BMR).
- Assessment of energy expenditure using the doubly labeled water technique.
Main Results:
- Parental feeding rate significantly increased with experimental brood size.
- Basal metabolic rate (BMR) increased with both manipulated brood size and individual feeding rate.
- A positive relationship was observed between BMR and energy expenditure.
- BMR increased disproportionately faster than available surplus energy for work.
Conclusions:
- The increased-intake hypothesis is supported, as marsh tits increase BMR with higher feeding rates to meet parental care demands.
- The substantial cost of high workload is not primarily due to energy reallocation from maintenance.
- The detrimental effects of high metabolic rates, such as oxidative damage, may represent the primary cost of sustained high workload.