舟山及其邻近岛屿獐种群的初步研究

舟山海岛上的獐(Hydropotes inermis),定海县志(1923)已有简要记录。作者在1978年调查时发现,舟山岛及其邻近较大的岛屿上普遍有獐,1976年海岛獐单位面积产量,5倍于浙江大陆邻近10个县的产量(盛和林,1981)。为进一步合理利用和发展獐资源,继而对舟山岛獐的种群结构繁殖和种群增长等问题进行研究,同时又对邻近10多个岛屿进行了访问调查,兹将初步结果报道如下。

A PRELIMINARY STUDY ON THE RIVER DEER POPULATION OF ZHOUSHAN ISLAND AND ADJACENT ISLETS

This paper provides some aspects of field work on the river deer(Hydropotes inormis) population, reproduction and harvest production. The results are summarized as follows.1. Body size. There is no remarkable difference in the body size of both sexes. The greatest skull length of adult males and females are 174.2±4.059mm(n = 20) and 173.8±5.966mm(n = 20), respectively.2. Sex ratio: The sex ratios of females, males of the island population is 1.095(n = l32).3. Age distribution. The age composition of the winter season shows that 47.7% of the river deer were yearlings, 36.5% were 2-year olds,8.3% were 3-year elds, 4.5% were 4-year elds, 5-year and 6-year olds were both 1.5%.4. Sexual maturity. Data on breeding showed that the male river deer were sexually mature at 5-6 months of age and the females at about 8 months of age. The males were found to mature earlier than "the females.5. Breeding season. The wild population of Zhoushan; Island indicated, that the rutting period occurs mainly during December and January. Adult males rut a month earlier than the young ones. The adult and youiid female river deer were found to be pregnant at various stages of gestation. Five out of the 9 adult females taken from February showed embryos, (55.6%), 6 female specimens of March all had developing embryos. None of the 8 young females collected during February were pregnant,,but specimens collected frcm March 1-15 showed that 2 out cf 4 yearlings had embryos, 4 females collected after March 16 were all pregnant.6. Reproduction rate. An examination of the 17 pregnant females based upon viable foetuses showed 52.9% commonly carried twins, 29.4% were triplets, 5.9% carried either single, quadruplet or quintuplet foetuses, respectively, an average of 2.53±0.9432 embryos in 17 female deer. Interviews with hunters showed that up to six fawns have been recorded in one birth which is exceptionally rare.7. Hunting pressure. The harvest period life table shows that the hunting pressure was rather high, the hunting rate were up to 47.7%, especially in the 2-year old age grcoip, the rate was up to 70%. Life expectancy was around one year in all age groups. The instantaneous rate of increase (r) = 0.5443, net reproduction rate(R₀) = 2.7596, mean length of a generation (T) = 1.8648, finite rate of increase(year) (A) = 1.7234, and the population doubling time (year) (t) = 1.2732.8. Survival conditions. Most of the islands lack large and medium sized carnivores, only Zhoushan and 2 other islands have a small population of leopard cats (Felis bengalensis) which may prey on the fawns. The only competition species are the Chinese muntjac (Muntiacus reevesi) of which only a small population exist on the Islands of Zhoushan, Putuo and Cuchiajian. The river deer are good swimmers and have a great ability of migration and expansion through adjacent islets to select and occupy suitable environment to survive, therefore, the natural mortality of the river deer is low.9. Harvest production. During the winter hunting season there are 450 -600 river deer hunted on Zhoushan archipelagos, and around 50 individuals are killed during other seasons as "pests". In summer 150-200 newly born fawns are killed to obtain colostrum for folk medicine. A recent survey shows that the estimated figure of annual kill is, about 650-850.