Age Structure and Body Size of The Tibetan Toad (Bufo tibetanus) Populations from Two Different Altitudes in China

Knowledge about the altitudinal patterns in age and body size helps to highlight the evolution of life history parameters in animals. In this study, we investigated the demographic traits of the Tibetan toad (Bufo tibetanus) between populations from low and high altitude habitats (2650 vs 3930m) using skeletochronology. We found 1) the mean age and body size of females were significantly greater than those of males in either population; 2) both sexes of toads from the higher altitude tended to be significantly older in age and larger in body size; 3) a significant positive relationship between age and body size within each sex of the toad at both altitudes; 4) growth rates varied between the two populations, with the higher rate observed in the low-altitude population, and lower in the high-altitude population. Our results suggest that factors other than age can influence altitudinal patterns in body size, such as altitude-associated temperature. Future research should pay attention to these factors and evaluate their influences on the growth patterns of animals.Knowledge about the altitudinal patterns in age and body size helps to highlight the evolution of life history parameters in animals. In this study, we investigated the demographic traits of the Tibetan toad (Bufo tibetanus) between populations from low and high altitude habitats (2650 vs 3930m) using skeletochronology. We found 1) the mean age and body size of females were significantly greater than those of males in either population; 2) both sexes of toads from the higher altitude tended to be significantly older in age and larger in body size; 3) a significant positive relationship between age and body size within each sex of the toad at both altitudes; 4) growth rates varied between the two populations, with the higher rate observed in the low-altitude population, and lower in the high-altitude population. Our results suggest that factors other than age can influence altitudinal patterns in body size, such as altitude-associated temperature. Future research should pay attention to these factors and evaluate their influences on the growth patterns of animals.