A vertebrate, the fence skink, is a common but relatively low-quality prey for an invertebrate predator, the redback spider

Many predators feed on a diversity of prey items and the traits of these prey can affect their quality for predators. While invertebrate predators most often feed on other invertebrates, numerous studies have documented spiders and other predatory arthropods feeding on vertebrates. The goal of this study was to examine the frequency of fence skinks, Cryptoblepharus virgatus, in the diet of redback spiders, Latrodectus hasselti, and to measure the amounts and ratio of nutrients that spiders extracted from fence skinks compared to representative high-quality (i.e., locust) and low-quality (i.e., beetle) arthropod prey. In field surveys, fence skinks represented 8% of individual prey items and 17% of the biomass of prey captured by redback spiders. In feeding trials, spiders consumed a lower total dry mass and mass of lipid when feeding on skinks relative to both arthropod prey and the lowest mass of protein when feeding on beetles. In terms of feeding efficiency, spiders were most efficient at extracting dry mass, lipid and protein from locusts and least efficient at extracting nutrients from skinks (lipid) or skinks and beetles (dry mass and protein). There were also differences in trace element consumption between spiders feeding on skinks versus locusts. These results suggest that skinks are a relatively low-quality prey. The frequency of skinks in the diet of these urban redback spiders is likely a consequence of the abundance of skinks in this habitat, similar microhabitat selection by spiders and skinks, and relatively indiscriminate predation by spiders. Further work is needed to examine the relative quality of other vertebrates for invertebrates and if other traits such as predator feeding mode affects the relative quality of vertebrates as prey.

Automated summary

A study found that fence skinks are relatively low-quality prey for redback spiders, as they consumed a lower amount of nutrients from skinks compared to other arthropod prey. The frequency of skinks in the spiders' diet is likely due to their abundance in the habitat and the indiscriminate predation behavior of the spiders.