Spatial encoding by bumblebees (Bombus impatiens) of a reward within an artificial flower array

Area of Science:

• Animal behavior
• Cognitive ecology
• Neuroethology

Background:

• Spatial memory is crucial for foraging in many species.
• Previous studies on spatial memory have involved various animals, including vertebrates.
• The role of different cues (scent, visual, egocentric) in insect spatial memory requires further investigation.

Purpose of the Study:

• To investigate how bumblebees (Bombus impatiens) utilize spatial cues for memory retrieval in a foraging task.
• To determine if bumblebees rely on scent marks, local spatial cues, or global environmental features to locate a rewarding target.
• To compare bumblebee spatial memory strategies with those of other species.

Main Methods:

• Bumblebees were trained to find a rewarding artificial flower (S+) among empty ones (S-) in a flight cage.
• Experiments manipulated the presence of scent marks (via flower covers) and the spatial arrangement of flowers.
• The colony's location was shifted between training and testing in one experiment to assess reliance on egocentric vs. allocentric cues.

Main Results:

• Bees consistently returned to the absolute position of the S+ (flower-array-independent position), irrespective of changes in surrounding cues or the removal of scent marks.
• The removal of scent marks reduced probing behavior, indicating their role in guiding immediate approach.
• Bees prioritized environmental features over egocentric information or the positions of S- flowers for locating the S+.

Conclusions:

• Bumblebees primarily use allocentric (environmental) cues to remember and relocate rewarding targets.
• Scent marks and local spatial configurations play a secondary role, influencing search behavior but not the primary memory of location.
• These findings highlight sophisticated spatial memory capabilities in bumblebees, comparable to those observed in vertebrates.