Visual and response-based navigation in the tortoise (Geochelone carbonaria)

Area of Science:

• Comparative psychology
• Neuroscience
• Herpetology

Background:

• Spatial cognition is well-studied in mammals and birds, with the hippocampus implicated.
• Reptiles lack a hippocampus, but their medial cortex may serve analogous functions.
• Limited behavioral research exists on reptilian spatial navigation and cue utilization.

Purpose of the Study:

• To investigate the role of extramaze cues in spatial navigation in the red-footed tortoise (Geochelone carbonaria).
• To compare reptilian spatial strategies with those observed in mammals and birds.

Main Methods:

• An eight-arm radial maze was used to test spatial navigation.
• Experiment 1 involved cue removal to assess reliance on extramaze cues.
• Experiment 2 reintroduced a rich-cue environment to observe strategy shifts.

Main Results:

• Tortoises initially employed a "turn-by-one-arm" strategy, unaffected by cue removal.
• In a rich-cue environment, this strategy decreased, and extramaze cue use increased.
• The observed response-based strategy differs from those seen in mammals and birds.

Conclusions:

• Reptilian spatial navigation, mediated by the medial cortex, may not directly parallel hippocampal functions.
• Tortoises exhibit unique spatial strategies potentially related to their neuroanatomy.
• Further research is needed to fully understand the evolution of spatial cognition across vertebrates.