Spatial learning is an important and complex skill in the animal kingdom, as it helps animals find a meal when food sources are scarce. Insects such as bees and ants that are social and live in communal nests are known to do this, and now we know some butterflies can as well. A study published August 7 in the journal Current Biology found that the Heliconius butterfly genus is capable of spatial learning.
According to the authors, the results provide the first known experimental evidence of long-range spatial learning for traplining in any butterfly or moth species. Heliconius or “passion vine” butterflies are tropical butterflies from South and Central America known for a variety of wing patterns. The beautiful creatures have evolved a novel foraging behavior amongst butterflies which includes feeding on pollen that utilizes large scale spatial information, according to the team.
“Wild Heliconius appear to learn the location of reliable pollen sources and establish long-term traplines,” study co-author and University of Bristol evolutionary neurobiologist Stephen Montgomery said in a statement. “Traplines are learnt foraging routes along which food sources are repeatedly returned to over consecutive days, an efficient foraging strategy similar to the behavior of some orchid bees and bumblebees. However, the spatial learning abilities of Heliconius, or indeed any butterfly, had not yet been experimentally tested.”
In the study, the team conducted spatial learning experiments in Heliconius butterflies over three spatial scales that each represented ecologically-relevant behaviors.
First, they tested the insect’s ability to learn the location of a food reward in a grid made up of 16 fake flowers. This test represented foraging within a single resource patch.
Next, the team increased the spatial scale and tested if Heliconius could learn to associate food with either the left or right side of a two-armed maze, to represent multiple plants at a single place.
Finally, they increased the distances and used a facility of outdoor cages called the Metatron in southern France to test if Heliconius can learn the location of good in a 196 foot wide maze shaped like the letter T. This set up represents foraging between places and is closer to the range Heliconius forages in in the wild.
The experiments that the Heliconius does show signs of spatial learning and can memorize the spatial location of their food sources. In future studies, the team plans to test if Heliconius are more proficient spatial learners than closely related species that don’t eat pollen. Understanding this would help reveal how enhanced cognitive abilities can be shaped by an animal’s ecology.
The team also plans to uncover the unknown mechanisms by which Heliconius navigates. Panoramic views and other visual cues are believed to be important for these butterflies, but the insects may rely on other cues such as a sun or geomagnetic compass in addition to what they can see.
“It’s been almost a century since the publication of the first anecdotal story on the spatial capabilities of these butterflies,” study co-author and Universidade Federal do Rio Grande do Norte biologist Priscila Moura said in a statement. “Now we are able to provide actual evidence on their fascinating spatial learning. And this is just the beginning.”