The effect of cannibalism on the demography and activity of a natural population of desert scorpions

Abstract

1. Cannibalism was studied over a five year period in a natural population of the scorpion, Paruroctonus mesaensis. Conspecifics are the fourth most frequent prey item and represent about nine percent of the diet; however when prey are ranked according to biomass captured, conspecifics are the number one diet item and constitute over twenty-five percent of all diet biomass. Cannibalism is a function of age, sex, size, time of year, scorpion density and level of available interspecific prey. 2. Several features of the population dynamics of P. mesaensis can be explained by cannibalism. Under natural conditions and in experimental enclosures, the mortality rate due to cannibalism increases with density and thus cannibalism is capable of producing population regulation. 3. Several behavioral characteristics function to decrease cannibalism: temporal and spatial aggregation of newborn animals; differential foraging phenology of subordinate scorpions; use of micro-habitat refuges by young animals; and components of male mating behavior. 4. It is suggested that cannibalism is potentially the most effective and homeostatic self-regulatory agent. There are several individual and group benefits which accrue to a population of cannibalistic individuals. Cannibalism is capable of contributing to the long term stability and persistence of populations.