SummaryWe generated a computer model to analyse the effects of 'shadow' competition for sit-and-wait predators, particularly antlion larvae. The model used a simple foraging assessment rule to determine the quality of an antlion's location, and antlions relocated randomly in their habitat when a location proved to be of low quality. Shadow competition, or competition for food caused when one sit-and-wait predator intercepts moving prey before a second sit-and-wait predator is encountered, was incorporated into the model by restricting antlions to a bounded arena, and having prey for the antlions enter from the arena periphery. Antlions responded to shadow competition by relocating their pits to peripheral areas of their habitat. This peripheral accumulation of pits was most pronounced when antlion densities were high, and when prey availabilities were infermediate. An experimental test with the antlion Myrmeleon immaculatus supported the importance of shadow competition as a cause of observed pit distributions. Only the treatment which incorporated shadowing had pit distributions nearthe periphery, while the pit distributions in the control treatments did not differ from randomly generated distributions. We conclude that shadowing can influence sit-and-wait predator distributions when the prey distributions and movement patterns generate the conditions necessary for shadowing. But when prey availability is unpredictable, making assessment of patches difficult, or when prey do not originate in the periphery of the habitat, other factors, such as temperature or moisture, could be more important.
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. To capture their prey, larval antlions invest energy in building and maintaining conical pit traps in fine-particulate substrate. The resident antlions (Myrmeleon immaculatus) at Sleeping Bear Dunes National Lakeshore, Michigan, USA, seldom relocated their pits, and we wondered whether this site fidelity could be understood as an optimal (or near-optimal) response to observed spatial and temporal variation in prey availability. To determine this, we considered a large number of compound foraging strategies, each composed of the number of days over which the antlion evaluates foraging success at a site; the weighted-average foraging success during this interval, below which threshold the antlion moves to a new site; and the length of the random walk taken by the antlion to a new pit location. Using Monte Carlo simulation, we determined the expected net energy gain from each of these strategies by antlions rewarded according to the field data set. The overall highest gain strategy generally agreed with our a priori expectations for the observed pattern of patchiness in prey availability over space and time. Moreover, the corresponding optimal frequency of pit relocation, 1.65 moves over the observation period of -8 wk, is in rough agreement with field observations. However, the gain surface was relatively flat: 60% of the investigated strategies yielded within 8% of the maximum gain. When costs of pit relocation were reduced, maximal gain strategies shifted to generate frequent movement, suggesting that the magnitude of such sampling costs may control the foraging strategy in environments with high spatiotemporal variability. by biological systems can be reduced to the need to gather resources, distributed across space and time, as efficiently as possible.Antlion larvae (Neuroptera: Myrmeliontidae), the focus of the present study, are generalist predators of arthropods that move along the soil surface. Larvae construct conical pits in the dry sandy or silty substrate and use them to capture prey. A large proportion of the antlion larval diet consists of ants, not because of any clear specialization or preference, but because ants are relatively abundant in the dry areas where antlions are found (Topoff 1977). Other prey frequently eaten by antlion larvae include spiders, beetles, isopods, flies, caterpillars, wasps, and mites (Turner 1915, Wheeler 1930, Heinrich and Heinrich 1984, Linton 1995.Prey are captured when they fall into the pit, are dragged under the sediment surface, and are digested externally. Digested prey fluids are then extracted from the prey and c...
To capture their prey, larval antlions invest energy in building and maintaining conical pit traps in fine‐particulate substrate. The resident antlions (Myrmeleon immaculatus) at Sleeping Bear Dunes National Lakeshore, Michigan, USA, seldom relocated their pits, and we wondered whether this site fidelity could be understood as an optimal (or near‐optimal) response to observed spatial and temporal variation in prey availability. To determine this, we considered a large number of compound foraging strategies, each composed of the number of days over which the antlion evaluates foraging success at a site; the weighted‐average foraging success during this interval, below which threshold the antlion moves to a new site; and the length of the random walk taken by the antlion to a new pit location. Using Monte Carlo simulation, we determined the expected net energy gain from each of these strategies by antlions rewarded according to the field data set. The overall highest gain strategy generally agreed with our a priori expectations for the observed pattern of patchiness in prey availability over space and time. Moreover, the corresponding optimal frequency of pit relocation, 1.65 moves over the observation period of ∼8 wk, is in rough agreement with field observations. However, the gain surface was relatively flat: 60% of the investigated strategies yielded within 8% of the maximum gain. When costs of pit relocation were reduced, maximal gain strategies shifted to generate frequent movement, suggesting that the magnitude of such sampling costs may control the foraging strategy in environments with high spatiotemporal variability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.