Comparative study of trophic behaviour and herd structure in wild and feral goats living in a Mediterranean island: Management implications

The aim of this study was to compare the trophic behaviour and the social structure of Majorcan wild goats and feral goats present in the island of Majorca. The former are descendants of an ancestral goat ecotype introduced in the island in the late Neolithic, whereas feral goats come from domestic forms introduced recently from the Iberian Peninsula. The study was conducted in four localities of the Serra de Tramuntana, a mountain range located in the northwest of the island of Majorca. Behavioural data were collected in three seasons, summer, winter and spring of 2011–2013, and when goat activity is at its peak, i.e., 3h after dawn and before dusk. The following variables were recorded: group composition (males, females, and kids) and activity (feeding, walking, resting, and watching). The proportion of time spent on each activity and their frequency were obtained from focal samples. Multivariate analyses of variance (MANOVA) were used to simultaneously analyse the activity variables. A total of 155 observations of 85 herds were registered throughout the study. A similar behaviour pattern has been observed in this study for the two goat ecotypes, feral and wild, apart from some seasonal variations in feeding and resting activities. In summer, feral goats showed higher feeding efforts (duration and frequency) than wild goats; this might be related to a lower efficiency obtaining feeding resources by the former, whereas wild goats, that have inhabited the island for millennia, coexisting with vegetation in periods of lower forage abundance and quality, would be more efficient herbivores during restrictive periods. Average herd size for both ecotypes is smaller than that recorded for domestic goat herds, suggesting a relatively low browsing damage compared to the latter. Also, feral goats apparently have a higher gregarious behaviour than wild ones, which might relate to their domestic origin. Currently, the management of goats on the island is based on maintaining the wild ecotype and eradicate the feral one, whose impact on vegetation is supposedly worse. However, our results show a similar trophic behaviour by both ecotypes, so that their impact on vegetation should also be expected to be similar, indicating that this argument has not enough scientific basis.