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Prey size selection and distance estimation in foraging adult dragonflies
R M Olberg1, A H Worthington, J L Fox
1Department of Biological Sciences, Union College, Schenectady, NY 12308, USA. olbergr@union.edu
Summary
Dragonflies visually assess prey distance, showing selectivity for prey size. This ability is crucial for hunting, with different species having varying distance estimation ranges.
Area of Science:
- Entomology
- Animal Behavior
- Sensory Ecology
Background:
- Dragonflies (Odonata, suborder Anisoptera) are visual predators.
- Understanding how dragonflies assess prey is key to their predatory success.
Purpose of the Study:
- To investigate if perching dragonflies visually estimate distance to prey.
- To determine the role of prey size and visual cues in dragonfly hunting behavior.
Main Methods:
- Presented artificial prey (glass beads of varying sizes) to perching dragonflies (Libellula luctuosa, Sympetrum vicinum) in field conditions.
- Videotaped dragonfly responses, recording take-off decisions and distances.
- Analyzed prey selection based on bead size and visual angle.
Main Results:
- Dragonflies exhibited high selectivity for bead size, preferring smaller beads for smaller species and larger beads for larger species.
- Prey rejection occurred for beads larger than the dragonfly's head, even if visual angles were similar.
- Distance estimation ranges were approximately 1 m for Libellula and 70 cm for Sympetrum.
Conclusions:
- Dragonflies can visually estimate the distance to potential prey items.
- Size and distance perception are integrated in prey selection.
- Mechanisms likely involve stereopsis and motion parallax from head movements.