Basic tools for navigation: use of landmarks in the domestic chicks

Pecchia, Tommaso

Basic tools for navigation: use of landmarks in the domestic chicks

Strumenti basilari della navigazione: uso di indizi locali nel pulcino di pollo domestico

Pecchia, Tommaso

2009-04-02

http://hdl.handle.net/10077/3089

Doctoral Thesis

Abstract

Examined were the capabilities of the domestic chick (Gallus gallus) to reorient in a rectangular array of landmarks. In the first series of experiments, the subjects were required to ground scratch at the correct location, defined by the configural cues, to gain a food reward. When the array occupied the centre of a circular enclosure, there were no evidence of geometric computation. Chicks reoriented when the landmarks occupied the corners of a rectangular arena. Nevertheless, when a rectangular array of undistinguishable cues was located centrally within a larger rectangular enclosure, the subjects failed to reorient. In the subsequent experiments, the reward was hidden inside one of the landmarks. The subjects should gain the access to the food through a hole in front of the cues. Surprisingly, the chicks encoded the geometric information in this circumstance. In the presence of multiple openings, the subjects accessed the landmark from fixed direction as they became experienced, suggesting the use of a view-matching strategy of navigation. This hypothesis was further examined presenting multiple geometric cues, given both by the shape of the enclosure and the shape of the array. At the end of the training, the subjects were observed after having selectively removed the one or the other geometric cue. The chicks failed to reorient on the basis of the residual information, sustaining the hypothesis previously mentioned. It is possible that chicks and other vertebrate species rely on egocentric representations to reorient both in the presence of isolated cues and extended surfaces.