The role of chemical cues in the predatory and anti-predatory behaviour of jumping spiders (Araneae, Salticidae).
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The role of chemical cues in prey-capture behaviour is studied in jumping spiders (Salticidae). Prior to this study, little attention has been given to how chemical cues influence the predatory behaviour of these spiders with complex eyes and visual acuity unrivalled in any other animals of comparable size. Three categories of predation are considered: salticids preying on conspecifics (cannibalism), salticids preying on non-conspecific spiders (araneophagy) and salticids preying on ants (myrmecophagy). Primary study animals are Portia spp. and Habrocestum pulex. Portia spp. and Habrocestum pulex are known to prefer spiders and ants, respectively, as prey, and each uses specialised prey-capture behaviour against its preferred prey. Here the predatory behaviour of these salticids is shown to be influenced in a variety of ways by chemical cues from prey. A general conclusion is suggested: that reliance on chemical cues is especially pronounced in predators that specialise on particularly dangerous prey. In Queensland, Portia fimbriata preys on other genera of salticids, with Jacksonoides queenslandicus being the dominant salticid prey species taken. Besides actively stalking J. queenslandicus in the open, P. fimbriata also launches attacks from webs and details of how P. fimbriata uses its web against J. queenslandicus are investigated. Contact and olfactory chemical cues from J. queenslandicus are shown to have three distinct effects on the predatory behaviour of Queensland Portia fimbriata: (1) attracting f. fimbriata to, or inducing f. fimbriata to remain in, areas where there are cues from J. queenslandicus; (2) changing f. fimbriata's behaviour in ways that facilitate prey capture; (3) heightening f. fimbriata's attention to optical cues from J. queenslandicus. No evidence was found that any other prey species has comparable influences on f. fimbriata. Undirected leaping (erratic leaping with no target being evident) is one of the Queensland P. fimbriata's responses to chemical cues from J. queenslandicus. That this behaviour functions as hunting by speculation is investigated. Experiments show that undirected leaping induces J. queenslandicus to move and thereby reveal its location to P. fimbriata. Intraspecific conflict in Sri Lankan Portia labiata is particularly violent, often ending in cannibalism. Using size matched conspecifics, two types of testing show that females of this species and population of Portia discriminate between conspecifics on the basis of fighting ability. Other Portia, and other salticid genera, were tested as well, but none of these are as prone to violent aggression and cannibalism. There was no evidence for recognition of fighting ability in any salticid other than Sri Lankan P. labiata. Habrocestum pulex is shown to rely on chemical cues from ants. Chemical cues from ants induce H. pulex to: (1) remain on soil which has previously housed ants; (2) enter an experimental arm of a Y-shaped olfactometer more often if it contains air from a cage with ants, or if it contains 6-methyl-5-hepten-2-one (an ant alarm pheromone); (3) change behaviour in ways that facilitate ant capture; (4) enhance attention to optical cues from ants.