Comparison of the capture efficiency, prey processing, and nutrient extraction in a generalist and a specialist spider predator

Abstract

Predators are traditionally classified as generalists and specialists based on the presence of adaptations that increase efficiency of prey capture and consumption and selection of particular prey types. Nevertheless, empirical evidence comparing foraging efficiency between generalist and specialist carnivores is scarce. We compared the prey-capture and feeding efficiency in a generalist and a specialist (araneophagous) spider predator. By using two related species, the generalist Harpactea rubicunda (Dysderidae) and the specialist Nops cf. variabilis (Caponiidae), we evaluated their fundamental trophic niche by studying the acceptance of different prey. Then, we compared their predatory behavior, efficiency in capturing prey of varying sizes, feeding efficiency, and nutrient extraction. Nops accepted only spiders as prey, while Harpactea accepted all offered prey, confirming that Nops is stenophagous, while Harpactea is euryphagous. Further, Nops displayed more specialized (stereotyped) capture behavior than Harpactea, suggesting that Nops is a specialist, while Harpactea is a generalist. The specialist immobilized prey faster, overcame much larger prey, and gained more mass (due to feeding on larger prey) than the generalist. Both the specialist and the generalist spider extracted more proteins than lipids, but the extraction of macronutrients in the specialist was achieved mainly by consuming the prosoma of the focal prey. We show that the specialist has more efficient foraging strategy than the generalist.

Venom gland size and venom complexity—essential trophic adaptations of venomous predators: A case study using spiders

“…Previous studies on venom metering in spiders revealed that generalists can alter the amount of venom injected based on the behaviour of prey; specifically agile, larger and dangerous prey required more venom to be paralysed (Kuhn‐Nentwig, Schaller, & Nentwig, ; Malli, Kuhn‐Nentwig, Imboden, & Nentwig, ). Some spider specialists catch dangerous prey (ants or spiders) (Pekár & Toft, ), and typically hunt prey larger than themselves (e.g., García, Viera, & Pekár, ; Michálek et al., ; Pekár, Šedo, Líznarová, Korenko, & Zdráhal, ). Thus, to effectively paralyse such prey, specialists should inject more venom than generalists.…”

“…Some spider specialists catch dangerous prey (ants or spiders) (Pekár & Toft, 2015), and typically hunt prey larger than themselves (e.g., García, Viera, & Pekár, 2018;Michálek et al, 2017;Pekár, Šedo, Líznarová, Korenko, & Zdráhal, 2014). Thus, to effectively paralyse such prey, specialists should inject more venom than generalists.…”

No ontogenetic shift in the realised trophic niche but in Batesian mimicry in an ant-eating spider

“…www.nature.com/scientificreports www.nature.com/scientificreports/ of authors (CRH) witnessed in the field capture of large ants by juveniles. There is gathering evidence that specialised spiders in general possess the ability to catch prey larger than themselves both in juvenile and adult stage 34,35 . For example, even small instars of ant-eating Zodarion spiders are able to catch giant ants 6 .…”

Nest usurpation: a specialised hunting strategy used to overcome dangerous spider prey

“…senilis only, because the number of adult individuals collected in the field was very low for the experiment. Although the trophic niche breadth may increase with age of spiders as bigger spiders can hunt bigger prey 21 , specialized spiders hunting dangerous prey like ants or other spiders are usually able to subdue larger prey than themselves even as juveniles 22–24 . Similarly, Poecilochroa was able to overcome larger spiders than itself as a juvenile.…”