Effect of adults on juvenile reproduction ofCalomys venustus(Muridae: Sigmodontinae)

Abstract

We tested the hypothesis that adult overwintering Calomys venustus inhibit maturation and reproduction in young-of-the-year from the first cohort. The study was carried out in four 0.25-ha enclosures (two control and two experimental), each situated on natural pasture. This study was conducted between August 1997 and March 1999 and had two parts: removal of overwintering male (ROM) and removal of overwintering female (ROF). For the ROM treatment overwintering males were removed immediately after the first cohort of juveniles were born, in the ROF treatment overwintering females were removed after the first cohort were weaned.Weekly censuses were taken for three successive days over 6 weeks. The sexual maturation and reproductive condition of juveniles were compared between treatments (overwintering male or female removal) using repeated-measures anova. The repeated measures factor was the age of juveniles. Removal of overwintering males and females did not affect sexual maturation of juveniles, however, overwintering males influenced the onset of reproductive activity of juvenile females at the beginning of the breeding period.

A demographic analysis of population responses to the manipulation of adult males in Calomys venustus (Rodentia, Sigmodontinae)

“…Control enclosures had lower survival probability than experimental enclosure II. This minor survival of control enclosures could be the result of reproductive activity began 20 days earlier than in experimental ones (Priotto et al 2006). The earlier beginning in reproduction activity in the presence of adult males would determine the minor survival because of greater physiological or Total recaptures 2 3 4 5 6 7 8 9 10 Enclosure I 1 7 5 0 1 0 0 0 0 0 0 6 2 10 4 3 1 0 0 0 0 0 8 3 5 5 0 0 0 0 0 0 5 4 17 13 0 0 0 0 0 13 5 23 11 1 0 0 1 13 6 17 5 0 0 0 5 7 25 8 2 0 10 8 15 7 1 8 9 3 3 1 6 1 6 Enclosure II 1 behavioral demands (in energetic terms), as it was observed in other mammal species (Lindstrom 1999;Lambin and Yoccoz 2001).…”

“…Considering that juvenile females reach sexual maturity 20 days earlier than juvenile males (Priotto et al 2006), in the absence of adult males the C1 females would become pregnant just when the C1 males reach sexual maturity. Therefore, the presence of adult males would be a limiting factor for females to start mating.…”

“…At the beginning of the breeding period, C1 females mate only with overwintering males because C1 males become reproductively mature 20 days later than C1 females (Priotto et al 2006). Overwintering males typically decline in number more rapidly than females (Provensal 2001;Priotto and Polop 2003) as it was observed in other rodent species (Krebs and Boonstra 1978;Redfield et al 1978;Beacham 1980).…”

Environmental variables and reproductive activity in small rodents of pampean agroecosystems

“…Trap sites and borders were classified as " active " or " inactive " in relation to the reproductive condition of the females of each species. At a microhabitat scale, trap sites were classified as active if at least one pregnant or lactating female was captured on it; a perforated vaginal orifice was not used as it is not a reliable indicator of reproductive activity (de Villafa ñ e 1981 , Priotto et al 2006 ). Trap sites were classified as inactive if no pregnant or lactating females were captured on it through the eight nights.…”