Home > Papers from 2016 > Do dung beetles need a ‘true’ compass?

Do dung beetles need a ‘true’ compass?

For navigating and migrating insects there are a plethora of celestial compass cues available to give orientation information. Sun position, polarisation patterns, chromatic gradients are all useful cues, but because they are all a consequence of sunlight, they tend to change in correlated ways. For instance the direction of polarisation is perpendicular to the azimuthal direction of the sun and the solar hemisphere is greeny (that’s the technical term) with the anti-solar hemisphere being bluey. If one uses these cues to infer a true compass direction then it is important to know how they they relate to each other and also how they change with the daily cycle. For instance, bees may forage in one direction in the morning when the sun is out. In the afternoon, they may need to remember this direction when the sun is occluded by clouds. Dung beetles don’t need a true compass because their task is simply to maintain a straight line as they roll their ball, they don’t care which straight line they choose and they only roll for a short period of time.

In this lovely new paper Basil el Jundi and colleagues showed that dung beetles use celestial information in a way that suggests they don’t combine compass cues into a unitary ‘true’ compass. Beetles set their rolling direction, and store the current celestial information, as they ‘dance’ on the top of their dung ball. But beetles don’t care if celestial cues are in unnatural combinations and they don’t transfer compass information from one modality to another. This raises the fascinating possibility that dung beetles have a proto-compass which may be an evolutionary precursor to the more sophisticated compasses of other insects.

 

el Jundi, B., Foster, J. J., Khaldy, L., Byrne, M. J., Dacke, M., & Baird, E. (2016). A Snapshot-Based Mechanism for Celestial Orientation. Current Biology.

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Categories: Papers from 2016
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