Observations on the reproductive activities, measurements, and growth rate of the Dikdik ( Rhynchotragus kirkii thomasi Neumann) *

S ummary.1  The observations in this paper are based on a collection of four hundred and twelve specimens of the East African Dikdik, Rhynchotragus kirkii thomasi Neumann, collected from the Shinyanga District of Tanganyika Territory. 2  The flesh and skull measurements are recorded, and there appears to be a sex dimorphism in size and growth rate. 3  The use of the closure and partial closure of certain skull sutures is proposed as a convenient index of age. On the basis of this index a comparison is made between the measurements of animals shot in the bush and those of captive specimens of known age. From this comparison it is tentatively concluded that the Dikdik reaches physical maturity before the end of the first year, and becomes sexually mature at about six months. Furthermore, although one captive Dikdik is recorded as surviving to the age of nine years two months, the present analysis suggests that the longevity of Dikdiks in the bush is more nearly five or less than five years. 4  The reproductive tracts of both the male and female are described, and the arrangement of the foetal membranes is noted. 5  The female is found to be polyoestrus throughout the year with two periods of intense breeding at the beginning and end of the rains respectively. The gestation period lasts about six months, and most females become pregnant twice yearly. Spermatozoa are found in the epididymides of the mature male at all times, but the testes, epididymides, and seminal vesicles show a seasonal rise and fall in average weight which corresponds in time with the breeding rhythm of the female. The significance of this is discussed.