Diet, distribution, and density of fallow deer (Dama dama) in the Caples Valley, Otago, New Zealand: implications for future management

Abstract

Fallow deer (Dama dama, L.) were introduced into the Wakatipu area in c.1887 and quickly spread throughout the Greenstone and Caples Valleys. By 1937 periodic culling of animals was undertaken to control numbers. Recreational hunters were given access into the valley in 1971 and in 1981 the Caples Valley along with the Greenstone Valley became part of the Wakatipu Recreational Hunting Area (RHA).

Since 1970 numerous studies have been conducted in the Caples to monitor fluctuations in animal numbers and vegetation health. During this study animal pellet counts were conducted to determine densities of animals in the valley; browse on vegetation was assessed and rumen samples were collected to determine diet preferences. Age and condition parameters were also collected from deer jawbones and hunter returns were used to assess hunting effort.

Since the last survey in the Caples in 1986/87 deer densities have increased slightly from 8.95% ± 1.81 % pellet frequency to 11.29% ± 2.14%. This change is not significant and numbers appear to be stabilizing. Current densities of deer are within the recommended levels (15% ± 4%) as suggested in the 1990 Wild Animal Control Plan, however, current deer densities are not compatible with habitat improvement. Many palatable species are becoming rare in the valley such as Griselinia littoralis. This species occurs in <1 % of forest plots in the <2m to >30cm tier but occurs in 20.71 % of the natural exclosure plots. As a result, some moderately preferred species are receiving more browse pressure. In 1989 Nothofagus species accounted for 0% of the total browse, however, in this recent survey they account for 7.8%; also Coprosma species which accounted for 47% of the total browse in 1989 now account for 69.4%. A lower population level of deer, than present, is needed if habitat condition is to improve and subsequently herd condition.

Extending the hunting season to include September, and increasing the bag limit from one deer per rifle to two, has allowed for a greater number of deer to be harvested annually. However, due to the low proportion of hunters returning permits ( <30% ), assessing whether current harvesting will lead to a decrease in numbers is difficult. A much higher proportion of permits need to be returned to achieve effective management.

Two possible options for future management in the Caples Valley are as follows. Reduce deer numbers substantially to improve forest condition and subsequently trophy potential. The second option is to maintain moderate densities that are consistent with current conservation objectives, and promote hunting for the younger generation to benefit forests elsewhere in New Zealand.

Possum densities have increased from 10.21 % ± 1.95% pellet frequency in 1986/87 to 13.98% ± 2.41 % in this recent survey. There has also been a spread of possums further up the valley into Kay Creek and Fraser Creek to areas where they were not formerly present. At present densities, possums are not recognized as a significant conservation threat in the valley, however, numbers should be carefully monitored.