Quantifying predation pressure along an urbanisation gradient in Denmark using artificial caterpillars

Abstract

Abstract. Urbanisation results in a marked modification of habitats and influences several ecological processes, some of which give rise to beneficial ecological services. Natural pest control, the effect of predators on prey is one of such services. We quantified changes in the incidence of predation with increasing levels of urbanisation using artificial caterpillars made of green plasticine. Potential predators can be identified by the "attack marks" they leave on these artificial caterpillars. We conducted this study from May to October 2010 around the city of Sorø (Zealand, Denmark), in forests along an urbanisation gradient (rural-suburban-urban). Artificial caterpillars were placed on the ground in order to obtain an estimate of the incidence of predation at ground level. Half (50%) of the 1398 caterpillars were "attacked" and 28.8% of the bites were those of chewing insects. We attributed the majority of these to carabids, the most common group of ground-active arthropods. Chewing insects exerted the greatest predation pressure in the original forest (52.1%), with lower values recorded in the suburban (10.1%) and urban (16.4%) forest fragments. Ants were responsible for only 4.7% of the attacks in forest, 11.3% in suburban and 16.4% in urban forest fragments. Mammals exerted the highest predation pressure in suburban habitats (22.2% vs. 4.9% in forest, and 8.1% in urban forest fragments).

Predation risk shaped by habitat and landscape complexity in urban environments

“…Although the latter result is in line with Ferrante et al. (), its explanatory power is low as indicated by the wide credible intervals (Figure g,h). Nevertheless, taken together, such findings may suggest that two communities of ground‐dwelling predatory arthropods with contrasting habitat preferences might have driven the observed pattern (Figure g,h).…”

A review of the sentinel prey method as a way of quantifying invertebrate predation under field conditions

“…We found that contrary to expectation, invertebrate predation increases from the Equator to the poles (H4 not supported), but the apparent increase at higher latitude is greatly influenced by data from a single study in Denmark (Ferrante et al ., ) that may or may not be typical of the situation in northern temperate forests. Further records are required, and geographical gaps have to be filled.…”

Predators do not spill over from forest fragments to maize fields in a landscape mosaic in central Argentina

“…We found a positive correlation between total and chewing insect predation rates and live plant ground cover (H5 supported). Ground cover is important for soil surface‐active arthropods (Magura, ), which are probably a key group attacking artificial caterpillars (Ferrante et al., ; Mansion‐Vaquié et al., ), and which are abundant in chaco serrano (E. González, personal observation). Plant material affects soil pH, humidity, and organic content (Sadler, Small, Fiszpan, Telfer, & Niemela, ), and it is usually preferred by invertebrates to bare ground.…”