Age group division and body ruler development of large gerbils in the southern margin of Junggar Basin

Rhombomys opimus is a typical family cluster living rat species in the desert ecosystem of Central Asia. Its feeding and mining activities cause serious harm to the desert ecosystem, and thus it is also one of the important plague sources in desert ecosystems. In this study, from 2022 to 2024, 150 large gerbils (♀ = 75, ♂ = 75) were captured on the southern margin of the Junggar Basin and their body weight, carcass weight, body length, tail length, back feet length, and ear length were measured. Cluster analysis was conducted with body weight as the main index, carcass weight and four body measures, and body weight, carcass weight and body size characteristics of each age group were analyzed by stepwise regression and Spearman correlation analysis. The results showed that: 1) The captured gerbils can be divided into four age groups, namely age group I (25 g < W ≤ 65 g, young), age group Ⅱ (65 g < W ≤ 95 g, subadult), age group Ⅲ (95 g < W ≤ 165 g, adult group I), and age group Ⅳ (165 g < W ≤ 246 g, adult group); 2) The body ruler index of the large gerbils was not synchronized throughout the growth and development period; 3) Weak relationships were found among hind foot length, ear length, and body weight at all growth stages of large gerbils: Therefore, when judging the age of the big gerbil cannot be referred to; 4) The body growth period is mainly during the age groups I, Ⅱ, and Ⅲ, whereas the growth period of the tail length is mainly during the age group Ⅲ; 5) When judging the age group of large gerbils with the characteristics of body ruler, Age I and Ⅱ age groups considering carcass weight and body length, For Ⅲ age groups, carcass weight, body length and tail length may be considered, Only the carcass weight was considered in the Ⅳ age group. This study provides a basis for the age division of gerbils and truly reflects the relationship between age and body ruler characteristics, which is of great significance for the prediction of local rat situation and the development of control measures.