Male Benefits?
Cannibalism of the male mantid is not an obligatory condition for copulation to occur (Maxwell 1998). So why then has cannibalism being maintained if it is not necessary? Whilst the benefits of sexual cannibalism for females are quite apparent, less obvious are the benefits to males and there are in fact several proposed benefits that males may derive.
Intriguingly males can indeed gain a reproductive benefit from being cannibalised (Maxwell 1998), and could be an adaptive mating strategy (Lawrence 1992). If males are voluntarily cannibalised it is indicative of parental investment to an extreme (Capinera 2008). Material donations provided by the male to his female partner serve as a form of parental investment; self-sacrifice has been proposed by some to be a nuptial donation (Welke & Schneider 2012). As the males body is utilised nutritionally by the female toward the production of offspring (Maxwell 1998). Willing cannibalism of the male may serve another purpose of prolonging copulation in order to increase his paternity share (Welke & Schneider 2012). Proposed by the male complicity hypothesis is that: “males shall engage in behaviour that actively facilitates, or at least passively fails to avoid, acts of sexual cannibalism during and after copulation” Lelito & Brown (2006, pp. 264).
Yet only if the male cannibalised is the sire will these strategies yield benefits to him (Welke& Schneider 2012). Studies have reported that copulation is still possible for males after the onset of cannibalism (Welke & Schneider 2012) and in some even prior to genital contact (Barry, Holwell & Herberstein 2008).
Sexual cannibalism also provides benefits to males if their chances of fertilizing additional females are low (Lawrence 1992), as cannibalism clearly imparts total loss of future reproduction (Lelito& Brown 2008). If the costs of finding and successfully mating with future females are high, more benefit maybe derived from cannibalism as a parental investment (Maxwell 1998).
Intriguingly males can indeed gain a reproductive benefit from being cannibalised (Maxwell 1998), and could be an adaptive mating strategy (Lawrence 1992). If males are voluntarily cannibalised it is indicative of parental investment to an extreme (Capinera 2008). Material donations provided by the male to his female partner serve as a form of parental investment; self-sacrifice has been proposed by some to be a nuptial donation (Welke & Schneider 2012). As the males body is utilised nutritionally by the female toward the production of offspring (Maxwell 1998). Willing cannibalism of the male may serve another purpose of prolonging copulation in order to increase his paternity share (Welke & Schneider 2012). Proposed by the male complicity hypothesis is that: “males shall engage in behaviour that actively facilitates, or at least passively fails to avoid, acts of sexual cannibalism during and after copulation” Lelito & Brown (2006, pp. 264).
Yet only if the male cannibalised is the sire will these strategies yield benefits to him (Welke& Schneider 2012). Studies have reported that copulation is still possible for males after the onset of cannibalism (Welke & Schneider 2012) and in some even prior to genital contact (Barry, Holwell & Herberstein 2008).
Sexual cannibalism also provides benefits to males if their chances of fertilizing additional females are low (Lawrence 1992), as cannibalism clearly imparts total loss of future reproduction (Lelito& Brown 2008). If the costs of finding and successfully mating with future females are high, more benefit maybe derived from cannibalism as a parental investment (Maxwell 1998).
Male mantids have the ability to mate with multiple females and as suggested by Lelito & Brown (2008, pp. 314) “the opportunity for surviving males to do so maybe enhanced by an increasingly biased sex ratio as the breeding season progresses”. There is wide ranging evidence for alternative male strategies that appear to substantially reduce the risk of cannibalism (Barry, Holwell & Herberstein 2008). As there is a net cost is imposed upon male fitness by sexual cannibalism, males could change their behaviour around and towards females in order to try and minimise cannibalisation risk (Maxwell 1998). A variation in mating behaviour according to the risk of cannibalisation imposed by the female occurs (Lelito & Brown 2006). ‘Safety precautions’ are one such behaviour undertaken by males when approaching or mounting females (Barry, Holwell & Herberstein 2008). That is in the presence of females they use low risk movements (Maxwell 1998), including slowing when approaching females, displaying a greater intensity of courting and mounting from a greater distance (Lelito & Brown 2008). During copulation they can also maintain a posture that keeps them safe from female reach (Maxwell 1998, Barry, Holwell & Herberstein 2008).
A second strategy is that of male choice, whereby males avoid mating with cannibalistic females altogether (Maxwell 1998). This involves males assessing the risk associated with a female (Lelito & Brown 2006). Well-fed females appear to be favoured by males given they are less likely to cannibalise and added to this often have high fecundity (Maxwell, Gallego & Barry 2010). Abdominal thickness is commonly an indication of this and alongside behavioural and chemical signals it is thought males cue to these to form the basis of their mate choice (Maxwell, Gallego & Barry 2010). However this is only viable under two conditions; the first being that males have access to other females and thus more than one mating opportunity, and secondly that these females differ in their fitness and propensity for cannibalism (Maxwell 1998). As a male will only benefit from rejecting a female and consequent mating prospect if a female with greater fecundity, and/or is less cannibalistic, can be found in the future (Maxwell 1998).
Male condition has also been considered an important predictor as to their behaviour and indeed risk of sexual cannibalism (Prokop & Radovan 2005). The higher their fitness thus prospective cannibalism decreases (Prokop & Radovan 2005). Overall males appear to be presented with a direct trade-off between the incentive to reproduce and motivation to live (Lelito & Brown 2006). In general their behaviour implies that they strive to increase the likelihood of surviving sexual encounters un-cannibalised (Maxwell 1998).
A second strategy is that of male choice, whereby males avoid mating with cannibalistic females altogether (Maxwell 1998). This involves males assessing the risk associated with a female (Lelito & Brown 2006). Well-fed females appear to be favoured by males given they are less likely to cannibalise and added to this often have high fecundity (Maxwell, Gallego & Barry 2010). Abdominal thickness is commonly an indication of this and alongside behavioural and chemical signals it is thought males cue to these to form the basis of their mate choice (Maxwell, Gallego & Barry 2010). However this is only viable under two conditions; the first being that males have access to other females and thus more than one mating opportunity, and secondly that these females differ in their fitness and propensity for cannibalism (Maxwell 1998). As a male will only benefit from rejecting a female and consequent mating prospect if a female with greater fecundity, and/or is less cannibalistic, can be found in the future (Maxwell 1998).
Male condition has also been considered an important predictor as to their behaviour and indeed risk of sexual cannibalism (Prokop & Radovan 2005). The higher their fitness thus prospective cannibalism decreases (Prokop & Radovan 2005). Overall males appear to be presented with a direct trade-off between the incentive to reproduce and motivation to live (Lelito & Brown 2006). In general their behaviour implies that they strive to increase the likelihood of surviving sexual encounters un-cannibalised (Maxwell 1998).