Individual success in mating balls of the grass snake, Natrix natrix: size is important

Abstract

Natricine colubrid snakes, including the grass snake, Natrix natrix, are frequently involved in complex social behaviour during the reproductive season. During these social behaviours, several males may simultaneously court a single female, resulting in a ‘ball’of mating snakes in which each male ‘combats’with rival males by ‘tail wrestling’(see Madsen & Shine, 1993). I performed some experiments in outdoor enclosures for testing the male‐male competition and the determinants of mating success in male grass snakes involved in such ‘ball’aggregations. I demonstrated that competition between males occurred both when a single female was available to multiple males and when two females were simultaneously available to males. The larger males achieved more copulations than the smaller ones, thus demonstrating that body size is a crucial determinant of the individual mating success. It was not clear which aspect of male body size is the most important in determining success in these mating ‘balls’, but it was evident that the age of the ‘fighting’male was not correlated with mating success. Larger females attracted more males than smaller ones, both in the field and in the enclosure. Furthermore, when the size difference between available females in the cage was high, only the largest female was courted and coupled.

Reproductive strategies in snakes

“…Even in species in which males do not show overt physical rivalry, such as natricine colubrids and boids in 'mating balls' of many males plus a female, more subtle physical struggles may influence reproductive success (Rivas & Burghardt 2001). For example, males may push aside the tails of their rivals, such that larger males obtain more matings than do smaller conspecifics (Madsen & Shine 1993a;Weatherhead et al 1995;Luiselli 1996;Shine et al 2000e). (iii) Alternative male mating tactics within a single population.…”

“…Lond. B (2003) vigorous physical battles (tail-wrestling; Madsen & Shine 1993a;Luiselli 1996;Shine et al 2000e). However, larger size might be a disadvantage if other males use body size as a cue to elicit courtship (Eunectes murinus; Rivas & Burghardt 2001).…”

The Opportunistic Serpent: Male Garter Snakes Adjust Courtship Tactics to Mating Opportunities

“…Males maintain this position with frequent attempts to intertwine their tailbase beneath that of the female; any movement by the female provokes an immediate urry of activity by male tails ('tail-searching': Noble, 1937;Blanchard & Blanchard, 1941;Crews & Gartska, 1982;Whittier et al, 1985). Large males may push the tails of their small rivals out of the way at such times (Luiselli, 1996;Shine et al, 2000f). The most distinctive courtship tactic by males involves caudocephalic waving, a series of muscular contractions that travel from the male's cloacal area to his head (Noble, 1937;Gillingham, 1987).…”

The blue‐spotted morph of the slow worm,Anguis fragilis:Colour polymorphism and predation risks

“…Considering that (1) male slow worms combat vigorously during the mating season for access to the females (Smith, 1951;Malkmus, 1995;Capula et al, unpublished data), (2) the blue-spotted morph is a typical male colouration, and (3) the blue spots are more conspicuous during the mating season (Naulleau, 1980; this study), we suggest that the blue-spotted colouration has a communication value and may increase life-time reproductive success in male slow worms. Moreover, if we hypothesize that male size is a crucial determinant of individual reproductive success during the mating season (as previously observed in other squamates; Andren, 1986;Olsson, 1992;Luiselli, 1995Luiselli, , 1996, it would be clear that the blue-spotted colouration occurs usually in large individuals with high contest success. It could be speculated that the value of the blue-spotted colouration is to communicate 'superiority' to potential rivals during the mating season.…”