Reproduction in the East African root rat (Tachyoryctes splendens ; Rodentia : Spalacidae) from Tanzania : the importance of rainfall

Abstract

The East African root rat, Tachyoryctes splendens (Rüppell, 1835) is a solitary subterranean rodent mole. The present study investigated breeding patterns in both sexes of T. splendens from data collected at monthly intervals over an entire calendar year. The study focused on the analyses from post mortem examination of males and females to assess the presence of foetuses, gonadal histology, reproductive tract morphometrics, measurement of gonadal steroids (plasma progesterone and oestradiol-17β in females and testosterone in males) and field observations (i.e., the presence of infants, juveniles, sub-adults and lactating females). The objective of this study was to assess if the reproductive biology of the root rat reflected the bimodal pattern of rainfall that is characteristic of East Africa. Rainfall has been suggested to trigger breeding in many subterranean rodents and as a consequence, this study aimed to assess the relationship between rainfall and reproductive characteristics of T. splendens. Peaks in mean gonadal mass, increases in concentration of reproductive hormones and the presence of Graafian follicles and corpora lutea in the ovaries of females, and testes mass, seminiferous tubule diameter and testosterone titre mirrored the annual peaks of precipitation at the study area. Together with field observations of the temporal occurrence of pregnancies, infants, juveniles and sub-adults, the data show that T. spendens cues its breeding with the patterns of rainfall, such that offspring are born in the latter half of each rainy season, from April to July and November to December.