Patch departure decisions by spice finches foraging singly or in groups

Area of Science:

• Behavioral Ecology
• Foraging Theory
• Animal Behavior

Background:

• The marginal value theorem (MVT) models optimal foraging, predicting foragers leave resource patches when intake rate drops below habitat average.
• A group version of the MVT suggests group foragers should leave patches sooner with less gain than solitary foragers.

Purpose of the Study:

• To test the MVT's predictions regarding patch departure decisions in group versus solitary spice finches.
• To investigate how group foraging affects resource exploitation and the influence of travel time.

Main Methods:

• Laboratory experiments using spice finches (Lonchura punctulata) in groups of three and alone.
• Patch exploitation was measured in two habitats with differing travel times between patches.

Main Results:

• Group foragers departed patches earlier and collected fewer seeds than solitary foragers, supporting MVT predictions.
• Resource sharing was unequal within groups, and group exploitation curves differed from solitary ones.
• Grouping reduced the impact of travel time on patch exploitation; one bird delayed departure, potentially for social reasons.

Conclusions:

• While group foraging aligns with some MVT predictions, resource sharing and exploitation dynamics are more complex than the model assumes.
• Group living may incur costs, such as increased variability in resource acquisition, but can also mitigate environmental factors like travel time.