Introduction to Filial Cannibalism - Using Fantail Darters for insight.

There comes certain circumstances in the animal kingdom where unfortunate things have to happen for the greater good; this occasionally includes filial cannibalism. There are two types of filial cannibalism: partial and total. Total  is where the parent consumes the total mass of offspring/litter whereas partial filial cannibalism is the consumption of only some (Lindstorm, 1997). A wide variety of animals eat their offspring including some carnivores, mammals and many others; most commonly know for however, is the occurrence of filial cannibalism in fish. Testing on fantail darters included the study of both fed and starved males. In the study they all ate their eggs but only 56% of the males completely disposed of their nest; the other 44% only consumed some of their offspring (Lindstorm, 1997). It was observed though that the difference in condition of the males (fed or starved) had little to no effect on the amount of egg consumption; in contrast it was noted that males with smaller egg masses ate the entire group whilst those with larger masses only ate some. In conclusion, filial cannibalism is generally unrelated to food ration. The reason males eat their young in the first place is to gain energy to complete their brood cycle; the males that eat their entire group of offspring tend to do so as the cost of energy needed to raise the young was too much compared to their breeding contribution.

Figure 1: Fantail Darter fish (Etheostoma flabellare) Retrieved from: http://www2.dnr.cornell.edu/cek7/nyfish/Percidae/fantail_darter.html 

Lindstorm, K., R. Sargent, C., 1997, Food access, brood size and filial cannibalism in the fantail darter, Etheostoma flabellare. 40: 107-110, ‘Behavioral Ecology and Sociobiology’. Retrieved 11th March 2014.

DID YOU KNOW?

Infanticide could more than likely be a heritable characteristic! The timing of mating behaviour in males, the male's familiarity with the female as well as the process of the male's ejaculation were all examined and have been seen to influence infanticidal behaviour!

Blumstein, D.T, 2000, The evolution of infanticide in rodents: a comparative analysis. Retrieved 10th March 2014.

Introduction to Infanticide

Infanticide refers to the murder of young by the parents in the animal kingdom, this type of behaviour has been noted in species such as lions, chimpanzees and even people. Many males within some species have been known to force their way into the alpha-male role and effectively result to killing any young that had been fathered by the previous alpha (Emlen, S. T., et al, 1989). This has been thought to have caused a return of sexual activity in females while increasing the fitness of the new male; the event of a committed infanticide serves some useful purposes. In the new domain of the uprisen alpha, the reproductive cycle in the females is sped up so that they are ready to mate again sooner than they would be if their previous young had been permitted to live (Crook, J. R., Sheilds, W. M., 1985).

Emlen, S. T., Demong, N. J. & Emlen, D. J. 1989. ‘Experimental induction of infanticide in female wattled jacanas’. Auk 106: 1-7.

Crook, J. R., Sheilds, W. M., 1985. ‘Sexually selected infanticide by adult male barn swallows’. Animal Behaviour 33: 754–761.