| Callosciurus erythraeus, also called red-bellied squirrel, belongs to Rodentia, Sciuridae and Callosciurus. In the recent years, red-bellied squirrels (Callosciueus erythraeus) have made great damage to artificial forests in Sichuan by debarking trees, mainly. Crypotomeria fortunei and Cunninghami lanceolata. Debarking retards the normal growth of trees, and even causes some trees to die. In order to develop an efficient and feasible method to protect the artificial forestry from harm of squirrels, we have conducted field studies of Callosciurus erythrarus bonhotei at the Hongya Forestry Farm. The paper propounds the reason for the damage of Callosciurus erythrarus bonhotei in the Hongya Forestry Farm and the indexes for age identification of Callosciurus erythrarus bonhotei, through analyses of stomach contents and morphlogocal growth indexes on 131 specimens of Callosciurus erythrarus bonhotei collected at the Hongya County Forestry Farm, Sichuan by gun shooting, as well as fieldwork from 2003 through 2004. The study on the stomach contents suggests that at the Hongya Forestry Farm, the damage to barks shows an obvious seasonal fluctuation, with highest in spring (30.61%) and lowest in summer (0.61%), reduced by 51-fold. In Hongya, in summer and autumn when red-bellied squirrels can find enough leaves, buds and fruits, they feed less on tree skins. But in winter and spring when leaves, buds and fruits are lacking, especially due to the low seed rate of Crypotomeria fortunei, red-bellied squirrels are compelled to damage the barks which they do not like, in order to meet the energy needs of passing the winter.Principal component analysis on the various growth indexes shows that, among 11 indexes of body measurements, skull measurements and lens weight which aresuitable to identify the ages of rodent animals, the projections of the basic length of skull are 0.933 and 0.954, respectively, which are all the highest growth index. The t-test on basic length of skull in both males and females shows no apparent difference. According to combination of the data of male and female basic length of skull and its frequency distribution, the red-bellied squirrels are classified into 4 age groups as following:â… : Whelp & sub-adult group: the basic length of skull is below 43.50 mm â…¡: Adult I group: the basic length of skull is between 43.51 and 44.60 mmâ…¢: Adult n group: the basic length of skull is between 44.61 and 45.80 mm â…£: Old group: the basic length of skull is above 45.80 mm Comparison between the classification and the original recorded reproduction of red-bellied squirrels shows that the basic length of skull in the skull growth index of red-bellied squirrels is suitable to be the index of age classification. We use the basic length of skull as the criterium to plot out the population of red-bellied squirrels of 2003 and find the mainly reproductive season of red-bellied squirrels is from March to October. July and August is the peak of reproduction. In red-bellied squirrel's population, adult II group is the most important group of all, not only for its high proportion in population but also its great contribution to population growth after winter.Observation of the development of cheek tooth and abrasion degree shows that the growth and abrasion of cheek tooth are different in different stages. Thus, the red-bellied squirrels can be classified into Whelp and adult groups according to the above index. The results of our study suggest that in practical work, we can make a crude age classification in accordance with the development of cheek tooth of red-bellied squirrels and then make a further classification by the basic length of skull index.
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