Density Effect on Postnatal Growth of Laboratory-Bred Yangtze Vole (Microtus fortis calamorum)

We performed four morphometric measurements to study the postnatal development of Yangtze vole Microtus fortis calamorum from birth through approximately 3 months of age with respect to growth. Vole pups were randomized into litters of 1-2 (LD, low density), 3-5 (MD, medium density), and 6-9 (HD, high density) individuals, and the body weight, body length, tail length, and hind foot length were measured and curve-fitted by using Von Bertalanffy and Logistic equations. Instantaneous growth rates and growth acceleration of Yangtze vole at different densities were calculated. Results showed that at different stages, the growth of the pups was density-dependent, while during the adult age, was independent of the presence of other individuals. The difference of hind foot length (HFL) between groups was not significant from day 21 while the body weight (BW) difference was significant or highly significant from birth to day 79, for body length (BL), it was significant from day 2 to day 86, and for tail length (TL), it was significant from day 4 to day 58, indicating that HFL reaches mature size ahead of BW, BL, and TL.