Elsevier

Animal Behaviour

Volume 83, Issue 1, January 2012, Pages 239-247
Animal Behaviour

Limb preferences and lateralization of aggression, reactivity and vigilance in feral horses, Equus caballus

https://doi.org/10.1016/j.anbehav.2011.10.033Get rights and content

Observational field studies were conducted on two remote populations of feral horses in Australia to determine whether lateralization is a characteristic of Equus caballus as a species or results from handling by humans. Group 1 had been feral for two to five generations and Group 2 for 10–20 generations. In both groups, left-side biases were present during agonistic interactions and in reactivity and vigilance. Therefore, as in other vertebrates, the right hemisphere appears to be specialized to control agonistic behaviour and responses to potential threats. The leftwards bias was stronger in measures of behaviour involving more aggression and reactivity. Preferences to place one forelimb in front of the other during grazing were also determined. No population bias of forelimb preference was found, suggesting that such limb preferences present in domestic horses may be entrained. Since stronger individual limb preferences were found in immature than in adult feral horses, limb preference may be modified by maturation or experience in the natural habitat. Stronger limb preference was associated significantly with elevated attention to the environment but only in younger feral horses. No sex differences in lateralization were found. The findings are evidence that horses show visual lateralization, as in other vertebrates, not dependent on handling by humans. Limb preference during grazing, by contrast, does appear to depend on experience.

Highlights

► Feral horses show left-side biases in agonistic responses, reactivity and vigilance. ► Leftwards bias was stronger in behaviour involving higher aggression and reactivity. ► No population bias of forelimb preference was found in the feral horses. ► Immature horses showed stronger limb preferences than adults. ► Limb preference was associated with elevated attention to the environment.

Section snippets

Location of the Horses

Feral horses were observed at two remote locations in Australia. Group 1 is at Mona Mona Aboriginal Mission (145°31′00″E, 16°43′30″S), approximately 50 km northeast of Cairns in North Queensland. These horses roam freely over an area of 50 km2 both within the mission, which covers 1595 ha, and in the surrounding State Forest. The habitat includes tropical rainforest, native woodland, a pine plantation and several small areas of open grassland. There is a small mission settlement and the horses are

Within harem bands

A total of 1886 agonistic interactions were recorded within harem bands for 18 feral horses from group 1 and 2557 for 48 feral horses from group 2. There was a mean of 1.5 left or right looking bouts per agonistic interaction. The mean ± SD number of left and right looking bouts scored per horse was 152 ± 105 for group 1 and 81 ± 73 for group 2.

Group 1 and group 2 did not differ significantly in the LI scores of looking bouts involving agonistic responses of any type (i.e. including threats and

Discussion

Feral horses displayed left-side biases of aggression, vigilance and reactivity (summarized in Table 2). These left-side biases correspond to right-hemisphere processing of agonistic behaviour, as well as vigilance and reactivity. Hence, feral horses follow the same pattern of lateralization found in other species (discussed by MacNeilage et al., 2009, Rogers, 2010). The leftwards biases of attack and reactivity were particularly strong (63% and 64%), consistent with the known right-hemisphere

Acknowledgments

The data were collected by N.A., who is grateful to the University of New England for financial support. This research was part of N.A.’s research towards a Ph.D. at the University of New England. We are grateful to Professor Gisela Kaplan for her advice and to the Djabugay Aboriginal People for giving permission to observe the feral horses on Mona Mona Aboriginal Mission and to the National Parks and Wildlife Service, especially Kenneth Pines, who gave permission to observe the feral horses

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