Researchers have witnessed several cases of spatial orientation in tarantulas – indicating that they may be capable of learning and memory.
They studied nine cases of the movement and hunting behaviour of arboreal (tree-dwelling) and fossorial (subterranean) tarantulas across North and South America, producing rare field-based observations of the creatures.
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On two occasions, the arboreal Aviculariinae tarantulas repeatedly left their retreats to hunt at more favourable areas up to two metres away – particularly at locations near artificial light sources that attracted more flying insects.
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Species that usually live in burrows within lowland floodplain areas also demonstrated unusual climbing behaviour. They scaled trees at heights of up to 12 metres, with the researchers concluding that they may have been foraging in the tree canopy.
While this has been previously observed to occur in the floodplain’s rainy season to avoid flooding, this behaviour was recorded during the dry season.
The researchers noted that the tree-climbing behaviour demonstrated by the fossorial tarantulas was different to the way they display ontogenetic niche shifts (changes in an animal’s habitat or behaviour that occurs as it grows from a juvenile to an adult).
After being disturbed, tarantulas were also observed returning to their burrows quickly and directly – this included the blind cave-dwelling species Hemirrhagus sprousei, which behaved in a similar way to the tarantulas with vision.
The researchers, Alireza Zamani from the University of Turku, Finland, and independent researcher Rick C. West, say their observations indicate that the tarantulas may have learned, retained and applied information from previous experiences to adapt their hunting behaviour.
This behaviour, known as spatial learning, has been reported in other arboreal tarantulas.
“Previous studies have shown that tarantulas can learn to avoid unpleasant stimuli, navigate complex mazes and remember spatial locations over time,” explains Alireza Zamani, the lead author of the study and researcher from the University of Turku, Finland.
“These abilities suggest that their nervous systems support more flexible behaviour than traditionally assumed.”
However, it remains unclear whether tarantulas use both allothetic (based on external environmental cues such as landmarks, or visual inputs) and idiothetic (internal body signals related to movement) cues to navigate back to their retreats, with different species appearing to use different forms of navigation.
The researchers also note that while their observations suggest that learning and memory may contribute to the described behaviours, the cognitive interpretation that they propose is still preliminary.
“Observations from the field, combined with controlled experiments, will be important for understanding how sensory cues, memory and experience interact to help these spiders navigate and search for prey,” concluded Zamani.
Top image: a blind cave-dwelling tarantula observed in Mexico. Credit: Rick C. West
