The influence of food supply on foraging behaviour in a desert spider
TL;DR: It is suggested that digestive constraints prevented supplemented spiders from fully utilizing the available prey, and by reducing foraging activities on the surface, spiders in a prey-rich habitat can reduce the risk of predation.
Abstract: We tested the alternative hypotheses that foraging effort will increase (energy maximizer model) or decrease (due to increased costs or risks) when food supply increased, using a Namib desert burrowing spider, Seothyra henscheli (Eresidae), which feeds mainly on ants. The web of S. henscheli has a simple geometrical configuration, comprising a horizontal mat on the sand surface, with a variable number of lobes lined with sticky silk. The sticky silk is renewed daily after being covered by wind-blown sand. In a field experiment, we supplemented the spiders' natural prey with one ant on each day that spiders had active webs and determined the response to an increase in prey. We compared the foraging activity and web geometry of prey-supplemented spiders to non-supplemented controls. We compared the same parameters in fooddeprived and supplemented spiders in captivity. The results support the "costs of foraging" hypothesis. Supplemented spiders reduced their foraging activity and web dimensions. They moulted at least once and grew rapidly, more than doubling their mass in 6 weeks. By contrast, food-deprived spiders increased foraging effort by enlarging the diameter of the capture web. We suggest that digestive constraints prevented supplemented spiders from fully utilizing the available prey. By reducing foraging activities on the surface, spiders in a prey-rich habitat can reduce the risk of predation. However, early maturation resulting from a higher growth rate provides no advantage to S. henscheli owing to the fact that the timing of mating and dispersal are fixed by climatic factors (wind and temperature). Instead, large female body size will increase fitness by increasing the investiment in young during the period of extended maternal care.
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TL;DR: In this article, the authors describe the links between the production of silk by spiders and their behaviour, and explain the phenomena of group cohesion, collective decision making, and coordination of activities, without resorting to mental representations for the overall situation.
Abstract: This article describes the links between the production of silk by spiders and their behaviour. Silk allows the spider to change its physical environment, which in turn leads to behavioural changes and impacts in the new environment. The feedback between silk and the animal producer can explain the architecture of spider webs and their adaptation to the environment, by referring only to stereotypic stimulus-response reactions without necessarily resorting to a “representation” by the animal of the structure it builds. Silk can act as a means of protection against environmental stress, a snare for prey, a means of locomotion, and also as support for chemical signals or to act as a vector of vibratory signals. These last two functions have undoubtedly played a key role in spider socialization and explains the phenomena of group cohesion, collective decision making, and the coordination of activities, without resorting to mental “representations” for the overall situation. The bulk of this review describes silk as the chief agent directing the construction of traps, communication, social cohesion, and cooperation amongst its producers.
30 citations
Cites background from "The influence of food supply on for..."
...However, it has been shown for a species of Eresidae from Namibia, that while its web is regularly destroyed by wind and sand it also adjusts the size of the trap according to the quantity of prey available, without changing the size of its retreat [205]....
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TL;DR: A significant positive correlation between sizes of webs and prey capture in Highprey spiders but not in Low Prey spiders is found, and the hypothesis that web investment by D. volucripes may incorporate information about both previous foraging effort and foraging success is presented.
Abstract: Foraging behaviors result from dynamic trade-offs made by organisms, incorporating factors such as past foraging success, reproductive effort, and predation risk. But, decision-making by animals occurs with incomplete information about the environment. We examined the relationship of web architecture and foraging decisions in the tangle web-building spider Dictyna volucripes Keyserling, a common spider in North American fields. Tangle webs are constructed over many days, which increases the total material and energetic investment in webs compared to orb-webs that are rebuilt daily. This reduces the profitability of changing web sites for tangle web spiders, making decisions about allocation of resources to foraging within single patches critical. We studied how foraging success affected investment in webs for High Prey spiders, fed two Drosophila daily, and Low Prey spiders, fed half that amount, over a 9-day period. We found no difference in the total area of silk added to webs. Increase in web area was proportional to initial web size in High Prey spiders, all of which increased webs by approximately 50%, despite substantial variation in initial sizes of webs. But, some Low Prey spiders with small initial webs increased web size by 200-300% while others, with large initial webs, invested proportionately little silk in webs. We also compared the effects of web architecture on prey capture of High and Low Prey spiders, under standardized prey density. There was no difference between High and Low Prey spiders in the number of Drosophila captured. We found a significant positive correlation between sizes of webs and prey capture in High Prey spiders but not in Low Prey spiders. We present the hypothesis that web investment by D. volucripes may incorporate information about both previous foraging effort and foraging success.
28 citations
TL;DR: In this article, the authors examined whether small juvenile amphipods can survive without parental care to determine if this reproductive strategy is obligate or facultative, and they found that extended parental care was obligate for the survival of early juvenile stages in this epibenthic amphipod.
27 citations
TL;DR: The large, dominant heteropodid, Leucorchestris, may determine many characteristics of the Namib arthropod community, including large size, polyphagy, low metabolism, longevity, brood care and seasonal foraging and breeding patterns.
25 citations
TL;DR: In areas with higher lionfish densities, prey fishes that are more active at dusk and/or inhabit seagrass beds near coral patch reefs may be more vulnerable to lionfish predation.
Abstract: Density-dependent changes in predator foraging behavior due to intraspecific com- petition for food can have important implications for population dynamics of both the predator and its prey. The Indo-Pacific red lionfish Pterois volitans is an invasive predatory reef fish that has reached high population densities and can cause large reductions in small native fishes. To deter- mine whether lionfish behavior or movement varies with local lionfish and/or prey densities, I con- ducted observations of lionfish on 16 coral patch reefs in The Bahamas. Lionfish foraging activity and movement varied significantly with lionfish density. At higher densities, lionfish exhibited greater activity levels, time away from shelter, and more short-term foraging movements between coral patch reefs and surrounding seagrass habitats. However, these changes were not uniform throughout the day, with differences in activity occurring only at dusk and differences in move- ment occurring at both dawn and dusk, but not midday. Although some lionfish foraging behav- iors varied with prey density, overall lionfish density was more strongly related to differences in lionfish activity patterns. These temporal and spatial changes in lionfish foraging behaviors are consistent with the predicted effects of intraspecific competition and may have important conse- quences for lionfish removal efforts and native prey populations. Specifically, in areas with higher lionfish densities, prey fishes that are more active at dusk and/or inhabit seagrass beds near coral patch reefs may be more vulnerable to lionfish predation. By culling lionfish, managers may reduce the local foraging movements of lionfish and thus help maintain native fish communities in multiple habitats.
23 citations
Cites background from "The influence of food supply on for..."
...Instead, individual lionfish spent more time hunting but less time active at higher prey densities, which suggests that they may spend less time searching for prey at higher prey densities (Anholt & Werner 1995, Lubin & Henschel 1996, Harding et al. 2007)....
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References
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TL;DR: In this article, age and size at maturity at maturity number and size of offspring Reproductive lifespan and ageing are discussed. But the authors focus on the effects of age and stage structure on fertility.
Abstract: Prologue Part I: Evolutionary explanation Demography: age and stage structure Quantitative genetics and reaction norms Trade-offs Lineage-specific effects Part II: Age and size at maturity Number and size of offspring Reproductive lifespan and ageing Appendices Glossary References Author index Subject index.
10,338 citations
TL;DR: The book aims to instill in students an ability to think through biological research problems in such a way as to grasp the essentials of the experimental or analytical setup to know which types of statistical tests to apply in a given case and to carry out the computations required.
Abstract: This text develops the science of biometry from an elementary introduction up to the advanced methods necessary for biological research and for an understanding of the published literature. This text is aimed primarily at the academic biologist including general zoologists botanists microbiologists geneticists and physiologists in universities research institutes and museums. This book while furnishing ample directions for the analysis of experimental works also stresses the descriptive and analytical statistical study of biological phenomena. It is intended both as a text to accompany a lecture course and as a complete course for self-study. The book aims to instill in students an ability to think through biological research problems in such a way as to grasp the essentials of the experimental or analytical setup to know which types of statistical tests to apply in a given case and to carry out the computations required. Chapters cover biological data data handling descriptive statistics probability estimation and hupothesis testing analysis of variance linear regression correlation multiple and curvilinear regression analysis of frequencies and miscellaneous methods.
4,145 citations
Book•
04 Feb 1993
TL;DR: The spider in the ecological play is a central character in the story of how spiders avoid competition and the impact of spiders on insect populations and competitionist views of spider communities are examined.
Abstract: Preface Acknowledgements 1. The spider in the ecological play 2. Hungry spiders 3. Competitionist views of spider communities 4. Failure of the competitionist paradigm 5. How spiders avoid competition 6. Impact of spiders on insect populations 7. Anchoring the ecological web 8. Untangling a tangled web 9. Spinning a stronger story References Index.
914 citations
TL;DR: This paper presents a meta- Ecology of Insect Folivores of Woody Plants: Nitrogen, Water, Fiber and Mineral Considerations, andritional Ecology of Grass Foliage-Chewing Insects and Phytophagous Mites.
Abstract: Nutritional Ecology of Forb Foliage-Chewing Insects Nutritional Ecology of Insect Folivores of Woody Plants: Nitrogen, Water, Fiber and Mineral Considerations Nutritional Ecology of Grass Foliage-Chewing Insects Nutritional Ecology of Phytophagous Mites Nutritional Ecology of Lichen/Moss Arthropods Nutritional Ecology of Arthropod Gall-Makers Nutritional Ecology of Bruchid Beetles Nutritional Ecology of Seed-Sucking Insects Nutritional Ecology of Stored-Product Insects Nutritional Ecology of Stored-Product and House Dust Mites Ecology of Nectar and Pollen Feeding in Lepidoptera.
793 citations
"The influence of food supply on for..." refers background in this paper
...The short pauses in activity may occur because time is required to digest the prey or to renew the digestive enzymes before resuming foraging (Riechert and Harp 1987)....
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01 Jan 1991
TL;DR: Barth et al. as discussed by the authors observed that the physiognomy or physical structure of environments has an important influence on the habitat preferences of spider species, and ultimately on the composition of spider communities.
Abstract: Spiders are extremely common inhabitants of most terrestrial communities, yet, compared to other animal taxa, they have only recently become the subject of ecological research (Turnbull, 1973; Witt and Rovner, 1982; Wise, 1984; Shear, 1986; Nentwig, 1987, for reviews). From the earliest studies, it has been clear that the physiognomy or physical structure of environments has an important influence on the habitat preferences of spider species, and ultimately on the composition of spider communities. This is certainly no coincidental observation for two important reasons:
1.
Many spiders build webs for prey capture, and the attachment of these webs to surrounding structures often requires the presence of specific architectural features or arrangements (Riechert and Gillespie, 1986).
2.
The nature of both web-building and non-web-building spiders’ primary sensory modalities (they perceive vibration through mechanoreceptors) dictates that they perceive their environment using tactile and vibratory cues (Barth, 1985).
403 citations