Experiment: Sexual Cannibalism in Spiders

The experiment was conducted to test three different variables. These variables are an assessment of female aggressiveness, food deprivation, and staged male to female interactions. When testing the female aggressiveness, virgin females were run through a latency of attack assay to determine their aggressiveness. The spiders were given 30 seconds and a cricket was dropped in and a measurement was taken of how long interaction occurred between the cricket and the spider. When testing food deprivation, the number of days that female spiders went without food varied and was paired in groups of 1, 3, and 5 days for routine feeding. It was predicted that the longer female spiders went without food, the hungrier they would be. When testing staged male and female interactions, the males were placed in female containers with open lids as an escape route. Each pair interacted for six hours and all pairs resulted in successful copulation, sexual cannibalism, or the male abandons the female’s web. All instances of cannibalism were precopula and occurred shortly after males initiated their courtship sequence. After interaction, the remaining males were taken out the female web and females that cannibalized a male were given 24 hours to feed on the male before being given another male. A female never cannibalized two males consecutively. It was concluded that females that attacked prey more rapidly were more likely to cannibalize their first male mate. There is no detection of an association between cannibalism or food deprivation and female’s body mass. There is a positive association between the mass of egg cases and the number of offspring in females. The study proved that two factor are important in sexual cannibalism, female hunger state and female aggressiveness. There is also a source of fitness benefit for the female.

The three variables influencing female behavior related to cannibalism are aggressiveness, food deprivation, and male-female interactions. Female’s aggressiveness is related to the aggressive spillover hypothesis. This suggests that sexual cannibalism emerges as a product of selection and sexual cannibalism could be a facet of aggressiveness. Selection that favors aggressiveness can indirectly increase incidence of sexual cannibalism. Under these circumstances, sexual cannibalism threatens to sterilize highly aggressive females. With male-female interactions, mate choice hypothesis comes as a theory. Sexual cannibalism may represent an extreme form of mate choice. This is when females attack undesired males but allow preferred mates to copulate. Lastly, food deprivation can occur in aggressive and nonaggressive females.