Attack rates on artificial caterpillars in urban areas are higher than in suburban areas in Colombia

Abstract

AbstractGrowing urban expansion can alter ecological processes within trophic networks. Predation on herbivores is known to vary with the size of the area covered by vegetation, successional stage, altitude and predator community structure; however there are gaps in understanding how this occurs in urban and suburban environments. The purpose of this study was to determine whether predation pressure on artificial models of caterpillars varied with the degree of urbanisation and type of substrate. Artificial caterpillars were placed on two types of substrates (leafvs. stem) in two areas of the city (urbanvs. suburban). Total predation was measured as the number of models with evidence of attack by predators, with the predation rate estimated on a weekly basis. Predation was affected by the degree of urbanisation, being higher in urban (x̄= 9.88%; SD = 4.09%,n= 8) than suburban areas (x̄= 5.75%, SD = 4.21%,n= 8). Attack marks were observed in 23.8% (n= 125) of artificial caterpillars. The weekly predation rate on leaves (x̄= 9.63%, SD = 5.95%,n= 8) was higher than that on stems (x̄= 6%, SD = 4.2%,n= 8). These results suggest that the incidence of predation might vary with the degree of urbanisation and by the type of substrate on which prey organisms are found.