Foraging strategies of animals can be influenced by multiple and diverse factors, such as competitive interactions, predator avoidance, and the abiotic environment. We studied niche partitioning among four species of orb-weaving spiders (Araneidae) in a grassland habitat: Argiope trifasciata (Forskal), Cyclosa turbinata (Walckenaer), Mangora gibberosa (Hentz), and Neoscona arabesca (Walckenaer). We determined whether the various species partition this niche by capturing different types of prey. They are sit-and-wait predators that often forage at night on the same insect taxa, thus they may compete for food or space.

Results/Conclusions

We found that webs of adult females of A. trifasciata, M. gibberosa, and N. arabesca tended to be positioned higher in the vegetation than were webs of juveniles. However, webs of C. turbinata showed the opposite pattern. Foraging characteristics, such as height of the hub of the web from the ground, diameter of the web, web-stitching, differ among species, providing evidence that these species occupy relatively narrow niches. Spider species differed in the number, size, and type of prey that they captured, even though stable isotope analysis indicated that they choose their prey from the same trophic level (i.e., herbivores). The number of prey captured per unit time was highest for spiders of small body size or those with large webs. Larger spiders caught fewer, but larger prey than small spiders.