Aspects of the feeding ecology of Himalayan tahr (Hemitragus jemlacicus), some comparisons with chamois (Rupicapra rupicapra rupicapra) and implications for tahr management in New Zealand

This thesis investigated aspects 'of the feeding ecology of Himalayan tahr (Hemitragus jemlahicus) and chamois (Rupicapra rupicapra) in the Southern Alps of New Zealand and some of the implications for management. Tahr and chamois were introduced to New Zealand in 1904 and 1907 respectively, to promote hunting and tourism. By 1937 they were declared pests because of their population increase and damaging impacts on native vegetation. Intensive, private helicopter meat-hunting in the 1970s reduced tahr numbers by 90%. Control of tahr is now done by the Department of Conservation. This study looked at food preferences of tahr by investigation of rumen contents from tahr shot at two privately owned high country sheep farms in the eastern Southern Alps and assessed differences in some of the physiological features of tahr and chamois heads as predictors of morphophysiological feeding type. It also looked at diurnal patterns in behaviour of tahr with emphasis on grazing bouts. Grasses made up over half the contents of tahr rumens from the two privately owned farms, with woody species in rumens close to double that of herbs. Measurements of various parts of the heads of tahr and chamois showed differences between these species and between the sexes within species. Differences in size, both absolute and relative were mostly associated with the considerably larger overall size of male tahr. Behavioural observations showed a general diurnal pattern in behaviour. Typically, feeding bouts occur at dawn and in the morning and resumed in the evening. The midday period, between main feeding bouts, are associated with resting at refuge sites. There is a transitional phase between feeding and resting periods associated with moving and vigilance behaviours. This transitional phase is more characteristic of smaller groups of tahr which generally move further between feeding areas and refuge sites. Grazing by tahr in large groups is more intensive than by small groups. This is due to prolonged grazing bouts and more time spent by individuals grazing compared with other behaviours. Correspondingly, vigilance behaviour of tahr is reduced in large groups. Tahr and chamois are probably intermediate feeding types. Although there are some differences between chamois and tahr in some of the physiological features these are probably not enough to associate these species with either concentrate selector or grass/roughage eater morphophysiological feeding type. A management approach for tahr control should be directed towards groups of female tahr. They cause the most damage to native plant communities in the subalpine environment because they are relatively sedentary and have a gregarious feeding strategy. Greater control efficacy can be achieved by focusing on removal of female tahr and reducing group size. Removal of females has a long term effect on the population by reducing both density and recruitment. Reduction of group size dilutes the impact on vegetation by limiting grazing pressure.