Death feigning in the face of sexual cannibalism

Abstract

Pre-copulatory sexual cannibalism by females affects male and female reproductive success in profoundly different ways, with the females benefiting from a meal and the male facing the risk of not reproducing at all. This sexual conflict predicts evolution of traits to avoid cannibalism and ensure male reproductive success. We show that males of the nuptial gift-giving spider Pisaura mirabilis display a remarkable death feigning behaviour—thanatosis—as part of the courtship prior to mating with potentially cannibalistic females. Thanatosis is a widespread anti-predator strategy; however, it is exceptional in the context of sexual selection. When the female approached a gift-displaying male, she usually showed interest in the gift but would sometimes attack the male, and at this potentially dangerous moment the male could ‘drop dead’. When entering thanatosis, the male would collapse and remain completely motionless while retaining hold of the gift so it was held simultaneously by both mates. When the female initiated consumption of the gift, the male cautiously ‘came to life’ and initiated copulation. Death feigning males were more successful in gaining copulations, but did not have prolonged copulations. We propose that death feigning evolved as an adaptive male mating strategy in conjunction with nuptial gift giving under the risk of being victimized by females.

The shield effect: nuptial gifts protect males against pre-copulatory sexual cannibalism

“…The use of fake gifts by males may thus be a way to get access to receptive females [18], but considering the results of the present paper it may also serve to reduce the risk of a cannibalistic attack. Pre-copulatory cannibalism against gift-carrying males was not observed in this study but has been observed previously [13][14][15]30]. Gift-stealing from these males was observed, however.…”

“…Because of low frequency of sexual cannibalism (less than 5%) [11,13 -15] the phenomenon was inferred to be an unimportant evolutionary force in this mating system. However, a low cannibalism frequency may be owing to effective male counteradaptations to avoid female aggression [15]. If the gift functions in the way that Bristowe [9] imagined, experimentally removing the gift should (all other things equal) expose the pre-adaptation risk of sexual cannibalism.…”

Young fire ant workers feign death and survive aggressive neighbors

“…However, a growing number of studies have reported instances of intraspecific death feigning. In several spider species, males freeze or feign death to gain copulations with potentially cannibalistic females (Bergey and Weis 2006;Bilde et al 2006). In the mantid, Mantis religiosa, males freeze after mating to avoid post-copulatory cannibalism by the female (Lawrence 1992).…”

Tonically immobilized selfish prey can survive by sacrificing others

“…This immobile state is variously called tonic immobility, hypnosis, thanatosis, catatonia, playing possum, playing dead or death-feigning. Catatonic animals can conceal their presence not only from predators (Miyatake et al 2004), but also from harassing mates (Dennis & Lavigne 1976) and from aggressive conspecifics (Lawrence 1992;van Veen et al 1999;Bilde et al 2006;Cassill et al 2008). However, until recently, research into the adaptive significance of tonic immobility has been bypassed in evolutionary studies (but see Miyatake et al 2004Miyatake et al , 2008Bilde et al 2006;Honma et al 2006;Ruxton 2006;Ohno & Miyatake 2007;Cassill et al 2008;Gerald 2008;Hansen et al 2008).…”