Reproduction and growth in a Neotropical arboreal mouse: Oecomys rutilus (Sigmodontinae: Cricetidae) in French Guiana

François Catzeflis

doi:10.1590/1676-0611-bn-2018-0697

Abstract

Abstract: Postnatal growth and development of the small Neotropical mouse Oecomys rutilus (Sigmodontinae: Cricetidae) were investigated from birth to day 143, in the laboratory. Morphometric measurements at age of 3 days, of both sexes combined, revealed body weight to be 3.4 ± 0.3 g, mean tail length as 27.4 ± 1.1 mm, and mean hind foot length as 9.3 ± 0.7 mm. Body weight was found to increase steadily until at least 69 days, whereas the instantaneous growth rates of other measurements declined earlier: the daily growth of hind foot length declined to a minimum at age of 24 days, and the growth of tail and of ear declined by the age of 33 days. Average litter size for 12 captive births was 2.5, ranging from 2 to 3. The preserved eye crystalline lens was weighted in 23 captive-born animals of known age, allowing a rough estimate of the age of reproduction in wild-caught animals. Based on the inferred relation between eye-lens weight and age, the youngest reproductive (pregnant) wild-caught females had an estimated age of 90 and 95 days.

Highlights

Being able to ascertain age is important in studies of mammals, as the knowledge of age structures of populations is necessary for understanding the life history strategies (Martin et al, 2011)
The growth pattern was examined in six external variables, for which a minimum of 3 young animals could be measured at each of 25 different ages ranging from 3 to 143 days after birth, and the mean values are detailed in Table 1. (For the body weight, data span a much longer period up to 567 days, with 42 additional ages, each with at least 3 measures)
In Oecomys rutilus, the average litter size measured in captivity is not different from the average number of embryos in wild-caught females

Summary

Introduction

Being able to ascertain age is important in studies of mammals, as the knowledge of age structures of populations is necessary for understanding the life history strategies (Martin et al, 2011). When samples of field-caught mammals are taken from a population, it is usually impossible to assign a known age to any specimen unless birth was observed and the individual was uniquely marked for later identification. The weight of the eye crystalline lens increases with age and many studies of age structures of populations have relied on weighing the lenses removed from mammal specimens (see Lord 1959 and review in Friend 1967; Morris 1972).

Methods

Results

Conclusion