Are Cape ground squirrels (Xerus inauris) induced or spontaneous ovulators?

Abstract

Little is known about the ovulation patterns in ground squirrels, even though the timing of ovulation could influence mate-order effects and sperm competition, which have been documented in a number of species. The Cape ground squirrel (Xerus inauris) is a social, nonhibernating, semifossorial rodent with aseasonal reproduction. Evidence suggests that sperm competition is an important aspect of male reproductive success in this species. We examined whether the Cape ground squirrel is an induced or spontaneous ovulator. Fifteen reproductive adult females were removed from natal colonies and housed individually. Females were subjected to 1 of 3 trials: no male contact, chemical and visual contact but no physical contact with intact males, or direct contact with epididymectomized males. Females from each of the 3 experimental treatments exhibited similar urinary progesterone metabolite concentrations and qualitative ovarian histology. Neither the presence of males nor copulation appear necessary for ovulation to occur, and ovulation in this social African ground squirrel appears to be spontaneous. © 2006 American Society of Mammalogists.