While humans may find the thought of cannibalism unsettling, other species seem to eat their own kind quite readily. Once viewed as a laboratory artifact, species specific predation is now being reevaluated. A recent study conducted by scientists at the University of Calgary, and published in the December issue of Ecology, has shown a definitive link between cannibalism and population stabilization among flour beetles.
Researchers Hugues P. Benoit, Edward McCauley and John R. Post studied twenty-one populations of the flour beetle, Tribolium confusum, in the laboratory. Their research built on the theory that cannibalism within this species is most likely to occur between mobile and immobile life stages; adult beetles mainly consume eggs and pupae, while larvae consume eggs.
When the beetles were separated according to life stage and a fixed proportion of the various stages were removed (temporarily) from the population, the incidence of cannibalism was dramatically reduced and in some instances almost entirely eliminated. In the absence of cannibalism, the growth of the adult population approached exponential rates. When the densities of larger larvae were relatively high, cannibalism of eggs was also very high, causing a large decrease in egg numbers. This resulted in a smaller population of larvae as these eggs hatched. This smaller population did not have a large cannibalistic impact on the subsequent egg population, resulting in little mortality, and consequently a large population of larvae some time later.
"As a result the population densities of eggs and larvae will cycle up and down, out of phase with one another, through time," explained McCauley.
Conversely, when the beetles were left to their own devices and allowed to eat flour and one another freely, population numbers tended to stabilize.
Similar studies have been conducted on populations of other animals. Past
research has indicated that size structured cannibalism
Contact: Nadine Lymn
Ecological Society of America