Cannibalism, Food Limitation, Intraspecific Competition, and the Regulation of Spider Populations

Abstract

Cannibalism among generalist predators has implications for the dynamics of terrestrial food webs. Spiders are common, ubiquitous arthropod generalist predators in most natural and managed terrestrial ecosystems. Thus, the relationship of spider cannibalism to food limitation, competition, and population regulation has direct bearing on basic ecological theory and applications such as biological control. This review first briefly treats the different types of spider cannibalism and then focuses in more depth on evidence relating cannibalism to population dynamics and food web interactions to address the following questions: Is cannibalism in spiders a foraging strategy that helps to overcome the effects of a limited supply of calories and/or nutrients? Does cannibalism in spiders reduce competition for prey? Is cannibalism a significant density-dependent factor in spider population dynamics? Does cannibalism dampen spider-initiated trophic cascades?

Predatory cannibalism in Drosophila melanogaster larvae

“…Our study suggests that the slowly developing genotypes would have both an opportunity and an incentive to cannibalize the fast developers, thus potentially contributing to the higher mortality of the latter and thus to maintenance of the polymorphism. Competition involving direct aggression stabilizes population dynamics and may help maintain species diversity 1,9,12 . The ephemeral resources on which D. melanogaster larvae feed in nature are often utilized by a range of other species 51,52 , and the behaviours we describe here in the context of intraspecific predation could also be involved in predation on larvae of other species, that is, intraguild predation 54 .…”

“…Although it can sometimes function to eliminate competitors 1,2 or be the price of mating 3 , it is usually a means of supplementing nutrition [4][5][6][7] . Cannibalism has important ecological consequences for population dynamics and stability, interspecific trophic interactions as well as pathogen transmission and epidemiology [8][9][10] .…”

Diet influences mate choice selectivity in adult female wolf spiders

“…Several recent studies, however, suggest that the nutritional quality of food can influence a variety of behaviors in arthropods, including courtship (Wagner and Hoback, 1999;Holzer et al, 2003;Hunt et al, 2004;Bertram et al, 2006) and mating (Mallard & Barnard, 2004). In addition, it has been suggested that predatory arthropods such as spiders are frequently nutrient limited in nature (Denno and Fagan, 2003;Fagan and Denno, 2004) and that food quantity is also often limited (Wise, 1993;Wise, 2006). These studies in combination with our results suggest that under natural conditions, food quantity and/or quality could significantly affect female mate choice and the evolution of male secondary sexual traits.…”

Dangerous mating systems: Signal complexity, signal content and neural capacity in spiders

“…Spiders have been reported to occasionally capture vertebrates: fish, bats, birds, lizards (Nyffeler and Knornschild, 2013), but they mostly prey on insects and other spiders (Wise, 2006). Cannibalism is common in spiders, and conspecifics can comprise a major component of their diet (Fox, 1975).…”

“…Cannibalism is common in spiders, and conspecifics can comprise a major component of their diet (Fox, 1975). Interspecific and intraspecific cannibalism affect population dynamics and are proposed to regulate density in many species (see Wise, 2006 for a review) with the exception of social or colonial spiders that show remarkable tolerance towards conspecifics (Bilde and Lubin, 2011). When cannibalism does occur, the relative size difference between two individuals often decides who eats whom (Dor and Hénaut, 2013).…”