Studies on the Population Reproduction Ecology of Plateau Pika

The studies on the reproduction ecology of Plateau pika (Ochotona curzoniae),as a part of a five-year (1984-1988) project of the behavioural ecology of the species,have been carried out at Heimahe area during from 1985-1988.The area we surveyed is near southwestern border of Qinghai Lake,Qinghai Province.The results of our investigations are briefly mentioned as follows:The beginning and ending of breeding period as well as the number of the pregnant time on Plateau pika usually varies with years according to our firsthand observations.From an analysis of the data on reproduction,it may be seen that the breeding population are composed mostly of the first and second litter of pikas born in the preceding year,occupying 57.14% and 25.71% respectively of the total number of the breeding population,while the remaining 17.15% consists of the third litter of pikas and old individuals.The range of the litter size of Plateau pika varies from one to eight young at a time,averaging 4.52±0.12.Usually three litters are produced by a female during one year,sometimes female can give birth to four or five litters.All the adult females are found to take part in reproduction.Altogether 2-29 young may be born in the females all life.The gestation period of the species is usually 22.2±0.13 days on an average.The suckling period in burrows where females breast-feed their young is 11.65±0.01 days based on our observations in the field.Only a few of first litter of young born in the present year,have been found to reach sexual maturation during summer.However,there are indications that the period of sex maturity of the females is earlier than that of the males (36.8±3.05 days as against 39.6±2.6 days on average).