An autecological study of bushbuck and common duiker in relation to forest management.

Abstract

Frequent reports of damage caused by bushbuck and common

duiker browsing on commercially important timber seedlings,

and an interest in the potential and feasibility of hunting

these two species on State land were the primary factors

responsible for the Directorate of Forestry's motivation of

this study. The study area at Weza State Forest comprised

approximately 21 000 ha of plantations, grasslands and

indigenous forests which were considered representative of

timbered areas throughout the Natal midlands.

Several methods of age determination were investigated

and these findings permitted assessments of growth, fecundity

and population structure. The physiological condition of

both antelope species was examined in relation to age, sex,

reproduction and management strategies, and the results

discussed in conjunction with mortality patterns. Principal

foods of both bushbuck and duiker were determined from rumen

analyses while 112 marked animals were regularly monitored to

facilitate assessments of habitat selection and levels of

spatial and social organisation.

of these largely solitary and

Estimates of the abundance

nocturnal antelope were

influenced by local movements in response to the availability

of food and cover which varied seasonally and also fluctuated

dramatically with forest succession and timber management

activities.

Although bushbuck and duiker bred throughout the year

and had almost identical rates of reproductive performance,

different factors were responsible in limiting the sizes of

these two populations. All the available evidence gathered

in this study indicated that food resources during winter and

early spring were inadequate for bushbuck, particularly in

1983 when 33% of the marked population died from starvation

and/or exposure. Notable differences in forage utilization

and habitat selection inferred little interspecific

competition at this time of the year.

In contrast,

territorial duiker appeared to be susceptible to highly

localised habitat modifications (including the availability of food and cover) which occurred throughout the year and

resulted from silvicultural and timber harvesting practices.

Rumen analyses and quantitative damage assessment

surveys revealed that browsing on timber seedlings was

usually confined to localised areas during the winter months

and was much less severe than had been originally suggested.

Conifers were regarded as a starvati~n food and methods of

reducing damage to these young trees were recommended for

potential problem areas.

Both antelope species were considered overabundant at

Weza and recommendations for the future management of these

populations included the limited utilization of surplus

animals, by sport hunting on a sustained yield basis, and

methods of manipulating and improving forest habitats.