Cognition in the barn: range use and its relation to cognitive performance in free-range broiler chickens (Gallus gallus domesticus)

Abstract

International audienceFree-range chickens are not all the same. Within the same group, under the same conditions, some individuals explore the range more than others. In many animal species, including chickens, individuals differ in behavior and cognition, i.e., how they perceive, process, and memorize information from their environment. We aimed to further understand the relationship between range use, spatial and non-spatial memory, and inhibitory control in two groups of free-range broiler chickens: those who frequently explore the range (‘high rangers, HR’) and those who prefer to stay in or near the barn (‘low rangers, LR’). Experiments were conducted on two flocks of broiler chickens (n=200 per flock) reared in similar conditions. To test spatial and non-spatial memory, an arena with 8 cups was used. During the training phase, individuals (nLR = 20, nHR = 21) learned that only a white cup among seven black cups was baited. To find the target cup, individuals could rely either on their spatial memory (the position of the cup in relation to the cues on the arena’s walls), or rely on their non-spatial memory (the color of the cup). Two probe tests, on two different days, for spatial memory (all cups are black) and non-spatial memory (the white cup changed its previous position) revealed that LR were quicker to visit the target cup during the spatial memory compared to HR (LR: 60.47 ± 44.58 s, HR: 80.60 ± 47.15 s; ranging level: t = − 2.21, p = 0.03; observation day: t = 0.36, p = 0.71). No differences between groups were found for non-spatial memory (Day 1: U = 195, p = 0.70, Day 2: U = 199, p = 0.77). To test inhibitory control, individuals (nLR = 7, nHR = 8) learned to detour either side of an opaque cylinder to gain a food reward. In the test condition, chickens were presented with a transparent cylinder in ten trials. As a sign of inhibition, subjects needed to refrain from trying to reach the food reward through the walls of the cylinder and detour to its open sides. LR were significantly more successful than HR (LR: 40 ± 12.90%, HR: 23.75 ± 9.16%, p = 0.028). Overall, our results show that LR chickens perform better in cognitive tasks compared to HR chickens. These results contribute to the growing body of research into the behavior and cognition of free-range chickens. This knowledge is essential for, ultimately, applying husbandry procedures that increase range use for all animals