Postnatal Growth and Development in a Subtropical Population of Peromyscus leucopus texanus

Abstract

Postnatal growth and development were studied in 41 litters of Peromyscus leuco- pus texanus from the Lower Rio Grande Valley (LRGV) of Texas. Data were recorded every other day for the first 2 weeks of life and thence weekly until an age of 105 days. Mean litter size of 3.5 was similar to means reported for most south-temperate populations of this species. Hearing and vision were established by 12 days of age, and running and climbing abilities were well developed by 2 weeks of age. Mean age at weaning was 21 days. Hindfoot length was the first dimension to reach adult size (28 days), followed by length of ear (35 days), length of tail (63 days), length of body (70 days), and weight (>77 days). Large litters did not grow at slower rates than small litters. Comparisons among populations of P. leucopus indicate that growth and developmental rates for most of the parameters studied are relatively similar throughout the range of the species. However, a population from Campeche, Mexico, exhibited more rapid morphological development than north-temperate and LRGV populations. The data suggest that adaptation to specific habitat fac- tors or availability of critical resources are of primary importance in determining rates of growth and development in Peromyscus leucopus. Peromyscus leucopus ranges from near the U.S.-Canadian border through eastern and central United States and southward to the Yucatan Peninsula.