| (Department of Bioengineering, Zhengzhou University, Zhengzhou,450001)(Institute of Biodiversity and Ecology, Zhengzhou University, Zhengzhou,450001)Age determination of wild animals is an important issue in researches of animal population ecology. Therefore, techniques for estimating the age of wild animals become very important for the studies of many aspects of population biology. But usually determining the exact age can be very difficult. Identifying each of individual and record the date of birth is the most accurate method to determine the age, but it is not easy to implement in the field. Because of the importance of the age determination for the study of population, we need to look for other ways. Recently, a new method by using the pellet size to determine the age of wild animals is developed. But its accuracy still needs to be proved. To test this methodology, we used house mice (Mus musculus) for the experiment. Based on the measurements of pellet’s length, diameter, weight and moisture capacity, the differences of pellets among the age groups and the differences of pellets between males and females in each group were compared. The measures were taken to determine if there are any relationship between age, sex and faecal pellet index in mice. So we can use traits of faecal pellet, including length, diameter, weight and moisture content to identify different age classes or sex of individuals. The relationship between age and nest building behavior of house mice is also compared.The major experiments, results and discussions are as follows:1By comparing the pellet length of house mice in different age groups, we found that there was a significant positive correlation between age and pellet length. The results show that the differences of pellet length were not significant between female and male house mice (F1.72=0.106, P=0.746). But among age groups, the differences were significant (F3.72=9.070, P<0.001). The interaction between age and sex were not significant (F3.72=0.639, P=0.592). The multiple comparison (LSD) showed that the pellet length of adult II group was greater than the young group (P<0.001), and sub adult group (P<0.001) and adult I group (P=0.001), while the differences among the other three groups were not significant.2By comparing the pellet diameter of house mice in different age groups, we found that there was a significant positive correlation between age and pellet diameter. The results showed that the differences of pellet diameter were not significant between female and male house mice (F1.72=0.063, P=0.803). But among age groups, the differences were significant (F3.72=5.407, P=0.002). The interaction between age and sex were not significant (F3.72=0.062, P=0.980). The multiple comparison (LSD) show that the pellet diameter of adult II group was greater than the young group (P=0.004), and sub adult group (P<0.001) and adult I group (P=0.005), while the differences among the other three groups were not significant.3By comparing the pellet weight of house mice in different age groups, we found that there was a significant positive correlation between age and pellet weight. The results revealed that the differences of pellet weight were not significant between female and male house mice (F1.72=0.225, P=0.637). But among age groups, the differences were significant (F3.72=10.721, P<0.001). The interaction between age and sex were not significant (F3.72=0.256, P=0.856). The multiple comparison (LSD) show that the pellet weight of adult II group was greater than the young group (P<0.001), and sub adult group (P<0.001) and adult I group (P=0.001), while the differences among the other three groups were not significant.4By comparing the pellet moisture of house mice in different age groups, we found that there was a significant positive correlation between age and pellet moisture. The results showed that the differences of pellet moisture were not significant between female and male house mice (F1,72=0.895, P=0.347). But among age groups, the differences were significant (F3,72=7.604, P<0.001). The interaction between age and sex were not significant (F3,72=1.734, P=0.168). The multiple comparison (LSD) indicated that the pellet moisture of adult II group was greater than the young group (P<0.001), and sub adult group (P<0.001) and adult I group (P=0.005), while the differences among the other three groups were not significant. 5The nesting behavior of house mice would happen in all age groups, especially in the sub adult group, which possibly derived from the need in reproduction during pregnancy and lactation period. On the other hand, the adult mice have relative strong ability adapting to the environment, and they did not exhibit active nesting behavior. |
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