Caatinga vesper mouse
The caatinga vesper mouse is a rodent species in the family Cricetidae from South America. It is endemic to eastern Brazil, where it is found in open savanna and thorny scrub habitats. Its karyotype has 2n = 66 and FN = 68. It was formerly synonymized with C. callosus, but the latter has 2n = 50 and FN = 66. Karyologic analysis of C. expulsus has shown that the X chromosome is large and submetacentric while the Y chromosome is either acrocentric or submetacentric. Predators include the barn owl. Sexual dimorphism in shape and size occurs; the former is present mainly before the age of 20 days. Males are smaller before age 50 days and larger thereafter, which becomes less prominent after 200 days.
