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Foraging in yellow dung flies: testing for a small‐male time budget advantage


Blanckenhorn, Wolf U; Viele, StuD N T (1999). Foraging in yellow dung flies: testing for a small‐male time budget advantage. Ecological Entomology, 24(1):1-6.

Abstract

1. Mating and foraging are generally mutually exclusive activities. Individuals are thus faced with a continuous trade‐off between time and energy expended in foraging and mating, but different phenotypes should respond to this trade‐off in different ways.
2. Sexual selection theory predicts that females should maximize their time and energy spent gathering resources, whereas males should maximize their time and energy spent obtaining mates, thus minimizing their time spent foraging, subject to the constraint that they need to forage minimally to sustain their activity.
3. Smaller individuals require less food to maintain their activity. Small males in particular could therefore increase mating effort at the expense of foraging effort and, all else being equal, may thus enjoy a time budget advantage relative to large males. On the other hand, larger individuals may compensate by being more efficient at finding prey and/or extracting nutrients.
4. The effects of sex, body size, and prey density on foraging time budgets of male and female yellow dung flies, Scathophaga stercoraria, were investigated in the laboratory.
5. Higher prey density (Drosophila melanogaster) resulted in reduced feeding (= handling) and hunting (= waiting or search) times for both sexes, as predicted by the marginal value theorem applied to foraging theory. Females fed longer on a prey item than did males, and also caught the next prey item more quickly. Large individuals extracted nutrients more quickly, but were not faster at catching prey. Small individuals satiated more quickly than larger individuals and also ate fewer prey items.
6. These results are largely consistent with the predictions and suggest a small‐male time budget advantage in the yellow dung fly. Integrating the various predictions to test directly for a small‐male time budget advantage is difficult in the laboratory, however, because hunting times are unlikely to reflect the natural situation. To what extent these results lead to increased probabilities for small males of obtaining matings in the field remains to be demonstrated.

Abstract

1. Mating and foraging are generally mutually exclusive activities. Individuals are thus faced with a continuous trade‐off between time and energy expended in foraging and mating, but different phenotypes should respond to this trade‐off in different ways.
2. Sexual selection theory predicts that females should maximize their time and energy spent gathering resources, whereas males should maximize their time and energy spent obtaining mates, thus minimizing their time spent foraging, subject to the constraint that they need to forage minimally to sustain their activity.
3. Smaller individuals require less food to maintain their activity. Small males in particular could therefore increase mating effort at the expense of foraging effort and, all else being equal, may thus enjoy a time budget advantage relative to large males. On the other hand, larger individuals may compensate by being more efficient at finding prey and/or extracting nutrients.
4. The effects of sex, body size, and prey density on foraging time budgets of male and female yellow dung flies, Scathophaga stercoraria, were investigated in the laboratory.
5. Higher prey density (Drosophila melanogaster) resulted in reduced feeding (= handling) and hunting (= waiting or search) times for both sexes, as predicted by the marginal value theorem applied to foraging theory. Females fed longer on a prey item than did males, and also caught the next prey item more quickly. Large individuals extracted nutrients more quickly, but were not faster at catching prey. Small individuals satiated more quickly than larger individuals and also ate fewer prey items.
6. These results are largely consistent with the predictions and suggest a small‐male time budget advantage in the yellow dung fly. Integrating the various predictions to test directly for a small‐male time budget advantage is difficult in the laboratory, however, because hunting times are unlikely to reflect the natural situation. To what extent these results lead to increased probabilities for small males of obtaining matings in the field remains to be demonstrated.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Scopus Subject Areas:Physical Sciences > Ecology
Life Sciences > Insect Science
Uncontrolled Keywords:Ecology, Insect Science
Language:English
Date:1 February 1999
Deposited On:22 Aug 2019 12:48
Last Modified:31 Jul 2020 03:32
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0307-6946
OA Status:Closed
Publisher DOI:https://doi.org/10.1046/j.1365-2311.1999.00171.x

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