The Hole Truth: Why Do Bumble Bees Rob Flowers More Than Once?

Area of Science:

• Ecology
• Plant-pollinator interactions
• Behavioral ecology

Background:

• Nectar robbing by animals bypasses floral reproductive organs.
• Multiple holes in single flowers are common, but the reason is unclear.
• Previous robbing may signal depleted resources, making repeat visits puzzling.

Purpose of the Study:

• Investigate why flowers are repeatedly robbed.
• Test hypotheses explaining multiple nectar-robbing holes in *Corydalis caseana*.
• Determine the profitability of robbing previously damaged flowers.

Main Methods:

• Field observations and data collection on robbing rates, floral longevity, and nectar accumulation in *Corydalis caseana* (Fumariaceae).
• Tested three hypotheses: (1) holes appear only after all flowers are initially robbed, (2) foragers make multiple holes per visit, (3) older flowers remain profitable despite prior robbing.
• Analyzed robbing hole accumulation over flower lifespan and nectar dynamics.

Main Results:

• Multiple holes appeared before most flowers were initially robbed, refuting hypothesis 1.
• 35% of additional holes appeared on subsequent days, indicating repeat visits beyond single-visit robbing, partially supporting hypothesis 2.
• Flowers refilled nectar consistently, making older flowers more profitable than younger ones, even if previously robbed, supporting hypothesis 3.

Conclusions:

• Older flowers remain more profitable for nectar robbers, explaining repeated damage.
• Nectar robbing damage clusters due to the consistent profitability of older flowers.
• This provides an explanation for repeated nectar robbing in *Corydalis caseana* and potentially other plant species.