Do polygynous males of Akodon azarae (Rodentia: Sigmodontinae) vary their mating tactics at low availability of females?

Abstract

We examined in Akodon azarae if at low availability of females (sex ratio biased toward males, 3:1), the mating tactics of males are determined by the number of receptive females to which they have access, or by the number of male competitors with which they interact. To test these hypotheses, we measured the home range size and overlap degree. At the beginning of the reproductive season, we studied spacing patterns using 57 and 30 home ranges established by reproductive males and females in three enclosure populations. We statistically compared our results with those previously obtained in enclosure populations with a sex ratio of 1:1. Male home range sizes were larger than those recorded in populations with a sex ratio of 1:1. The degree of male intra-sexual overlap increased about 3.5 times with respect to that observed under a sex ratio of 1:1. The increase in home range sizes and intra-sexual overlap degree of reproductive males reflects that A. azarae males may adjust their spacing strategy to increase their mating opportunities at low density of females. Our results suggest that at low breeding female availability, male mating tactics could be determined by the number of receptive females to which they have access.

Female Intrasexual Territoriality and its Potential Adaptive Significance: The Pampean Grassland Mouse as an Ecological Model Species

“…Taken together, current evidence is more consistent with the hypothesis that A. azarae breeding females are aggressive against intruder females as a strategy to protect their offspring, a possibility that could explain interfemale spatial avoidance recorded both in wild and in enclosed populations of this species (Priotto & Steinmann ; Bonatto et al. , ; Ávila et al. ).…”

“…Nevertheless, these authors found that during behavioural trails, both resident and intruder females spent most of the time exploring the environment, suggesting tolerant coexistence. Taken together, current evidence is more consistent with the hypothesis that A. azarae breeding females are aggressive against intruder females as a strategy to protect their offspring, a possibility that could explain interfemale spatial avoidance recorded both in wild and in enclosed populations of this species (Priotto & Steinmann 1999;Bonatto et al 2012Bonatto et al , 2015Avila et al 2016).…”

“…Akodon azarae has a polygynous mating system that operates through female defence, in which a minority of males (40%) monopolize several fertile females leaving other males without access to them (Bonatto et al 2012(Bonatto et al , 2013a. In this species, during the breeding period, male home range sizes are always larger than females (240 and 160 m 2 , respectively), show longer movement distances than females (63.5 and 25.6 m, respectively) and female intrasexual overlap percentages are always lower than those of males (7% female/female and 12% male/male) (Priotto & Steinmann 1999;Gomez et al 2011;Bonatto et al 2012Bonatto et al , 2015Avila et al 2016). According to Batzli & Henttonen (1993), an overlap degree significantly lower than the expected by random placement (minor than 10%) would indicate that individuals are avoiding one another (keeping exclusive or non-overlapping home ranges).…”

Space Use and Social Mating System of the Hantavirus Host, Oligoryzomys longicaudatus

“…In species where males have larger home ranges than females and extensively overlap with both female and male home ranges, researchers proposed a promiscuous mating system (Bond and Wolff 1999;Wolff and Macdonald 2004;Steinmann et al 2005;Blondel et al 2009). In contrast, in species where males have larger home ranges than females but keep mutually exclusive home ranges that extensively overlap with more than one female home range, it was proposed a polygynous mating system, in which a minority of males control or gain access to multiple females leaving other males without access to them (Ostfeld 1986;Shier and Randall 2004;Loughran 2007;Wolff and Sherman 2007;Bonatto et al 2012Bonatto et al , 2015.…”

“…A greater degree of imbalance in the OSR leads to a greater expected variance in reproductive success among members of the limited sex, affecting directly the degree of polygyny (Trivers 1972;Clutton-Brock and Parker 1992;Mitani et al 1996;Aloise King 2013). Many studies at the population level have revealed the impact of population density and OSR on spacing and mating behaviours of vole and mice (Ochiai and Susaki 2002;Steinmann et al 2006a, b;Stradiotto et al 2009;Sommaro et al 2010;Steinmann and Priotto 2011;Bonatto et al 2015;A ´vila et al 2016). For example, in some promiscuous and polygynous vole species, male home range size and overlap degree are negatively correlated with population density (Ostfeld et al 1985;Ostfeld 1986;Nelson 1995a, b;Bond and Wolff 1999;Moorhouse and Macdonald 2008;A ´vila et al 2016) and receptive female availability (Steinmann et al 2006a;Steinmann and Priotto 2011), while females maintain the size and exclusivity of its home ranges regardless of population density (Saitoh 1981;Ostfeld 1985;Erlinge et al 1990;Sommaro et al 2010;A ´vila et al 2016).…”