Why sexual cannibalism?
Sexual cannibalism as extreme as it is, has many advantages for species that allows them to persist and flourish in environments today. Such advantages include the ability of the process to adjust demographic structure, population numbers and processes, life histories and resource usage. Inversely sexual cannibalism does come with certain risks and drawbacks, including the obvious male counterparts life coming to an end. Below are some suggestions to the advantages and disadvantages of this act, and the implications this strategy may have on the praying mantis species.
The advantages of sexual cannibalism
- By eating a male at mating the female increases her fecundity by increasing egg case mass. Research has shown female body conditions also improved which allowed for a significant increase in the mass of oothecae when compared to non cannibalized examples, thus increasing fecundity as well as number and health of the offspring (Johns & Maxwell 1997) (Barry et al' 2008).
- Valuable nutritional benefits from the male, of help when food resources may become scarce due to overcrowding and competition from other species (Barry et al' 2008).
- Population size control allows for optimal carrying capacity in certain habitats.
- As larger males are more often spared, keeps fitter genetic material flowing among populations (Prenter et al' 2006).
- Allows for natural selection to take place, due to preference orientated cannibalism.
- Allows for adaptive behavioral evolution to take place in individuals, often witnessed in the apparent attempt by males to escape cannibalism via sneak approaches when copulating (Kynaston et al' 1994).
- Increase of general fitness in offspring from the consumption of males leads to greater adaptive ability in remaining species, increases resilience to change and allows for a strong genetic population to adapt to future conditions, thus increasing the persistence of this species when faced with varying conditions/impacts such as climate change, competition, and resource depletion (Prenter et al' 2006) (Kynaston et al' 1994).
The disadvantages of sexual cannibalism
- Loss of future reproductive opportunities (Suttle 1999).
- Cannibalism may reduce the chances of eggs being fertilized due to the consumption of the male before or during copulation.
- No direct benefit for the male from sexual cannibalism (Johns & Maxwell 1997).
- Potential transmission of pathogens from the consumption of the male that may be harmful or induce death.
- Cannibalization of just males may lead to a biased 'feminizing' sex ratio, due to decreasing numbers of potential male mates once consumed (Hurd et al' 1994).