Abstract
Human and non-human animals are capable of using basic geometric information to reorient in an environment. Geometric information includes metric properties associated with spatial surfaces (e.g., short vs. long wall) and left-right directionality or ‘sense’ (e.g. a long wall to the left of a short wall). However, it remains unclear whether geometric information is encoded by explicitly computing the layout of surface geometry or by matching images of the environment. View-based spatial encoding is generally thought to hold for insect navigation and, very recently, evidence for navigation by geometry has been reported in ants but only in a condition which does not allow the animals to use features located far from the goal. In this study we tested the spatial reorientation abilities of bumblebees (Bombus terrestris). After spatial disorientation, by passive rotation both clockwise and anticlockwise, bumblebees had to find one of the four exit holes located in the corners of a rectangular enclosure. Bumblebees systematically confused geometrically equivalent exit corners (i.e. corners with the same geometric arrangement of metric properties and sense, for example a short wall to the left of a long wall). However, when one wall of the enclosure was a different colour, bumblebees appeared to combine this featural information (either near or far from the goal) with geometric information to find the correct exit corner. Our results show that bumblebees are able to use both geometric and featural information to reorient themselves, even when features are located far from the goal.
Highlights
When nongeometric information is added to the rectangular enclosure, for instance a differently coloured wall or a conspicuously different panel located at the corner, animals appear to be able to combine geometric and featural information to distinguish between geometrically equivalent corners
No significant difference was apparent in first choice frequency between the correct corner, C, and its geometrically equivalent corner R (F(1,9) = 1.569 P = 0.242), indicating that the disorientation procedure was effective and that bumblebees did not rely on any extra- or intra-enclosure featural cues
Bumblebees distinguish between geometric equivalent locations (C and R) when tested in the presence of featural information, both near and far from the goal (Exp. 2)
Summary
Following the seminal work by Cheng [1] a variety of vertebrate species have been shown to be able to reorient in space using geometric cues, i.e. using metric properties of surfaces, such as choosing between a short wall and a long wall, and sense discrimination, such as choosing between turning to the wall located to left or right, including fish: [2,3,4,5]; domestic chicks: [6,7,8,9]; pigeons: [10,11]; rhesus monkeys: [12]; rats: [13,14]; human children: [15,16,17,18,19,20] In these studies, animals are first allowed to locate a hidden goal at one of the corners of a rectangular enclosure, in the absence of extra-enclosure cues (landmarks). Reliance on geometric (rather than featural) information is more pronounced in small enclosures [21,22], but in general use of geometry appears to be almost universal [23] and observed at birth in vertebrates [24,25,26,27]
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