Project Title

Temporal Factors Affecting Foraging Patterns of a Diurnal Orb-weaving Spider, Micrathena gracilis (Araneae: Araneidae)

Authors' Affiliations

Mitchell Long, Department of Biological Sciences, College of Arts and Sciences, East Tennessee State University, Johnson City, TN Thomas C. Jones, Department of Biological Sciences, College of Arts and Sciences, East Tennessee State University, Johnson City, TN Darrell Moore, Department of Biological Sciences, College of Arts and Sciences, East Tennessee State University, Johnson City, TN

Faculty Sponsor’s Department

Biological Sciences

Name of Project's Faculty Sponsor

Dr. Thomas Jones

Additional Sponsors

Darrell Moore

Type

Poster: Competitive

Classification of First Author

Undergraduate Student

Project's Category

Circadian Rhythms

Abstract Text

Many studies have investigated the ecological factors that affect behavior in Micrathena gracilis, a diurnal orb-weaving spider that forages exclusively on flying insects during the day. However, none yet have considered how the temporal distributions of prey and predator occurrences shape their daily behavioral rhythms, especially web construction which involves a heavy energetic investment well in advance of potential nutritional benefit. Recently, other spider species have been found to express significant circadian plasticity, suggesting that circadian clock-controlled rhythms may play a larger role in niche partitioning than once thought. Despite the appearance of significant insect abundance in the evenings, M. gracilis individuals stop foraging, take down their webs, and retreat before they can capitalize on this opportunity. Is the nutritional benefit of this forfeited prey significant compared to what they collect during the day, and if so, what potential cost might justify opting out of this potential gain? To investigate, sticky traps for prey collection and a camera array for recording predator activity were used at a local field site to survey what risks and rewards these spiders face throughout the 24-hour day. Spider activity in a lab environment and web captures in the field were also used to confirm behavioral patterns and nutrient uptake throughout the day. It was found that significant prey biomass is given up shortly after the time that spiders typically retreat, suggesting that the spiders truly forfeit this prey and do not simply retreat due to a gradual decrease in overall prey availability. Spiders reliably cease foraging in the early evening and show agitation throughout the night when not comfortably hidden, suggesting that significant extension of foraging behavior may be harshly punished. However, recorded predation events from the camera array were much rarer than anticipated, and no predation was confirmed in the evening. These results support the notion that these spiders’ circadian rhythms are shaped by factors other than prey availability, but more work is necessary to identify these factors

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Temporal Factors Affecting Foraging Patterns of a Diurnal Orb-weaving Spider, Micrathena gracilis (Araneae: Araneidae)

Many studies have investigated the ecological factors that affect behavior in Micrathena gracilis, a diurnal orb-weaving spider that forages exclusively on flying insects during the day. However, none yet have considered how the temporal distributions of prey and predator occurrences shape their daily behavioral rhythms, especially web construction which involves a heavy energetic investment well in advance of potential nutritional benefit. Recently, other spider species have been found to express significant circadian plasticity, suggesting that circadian clock-controlled rhythms may play a larger role in niche partitioning than once thought. Despite the appearance of significant insect abundance in the evenings, M. gracilis individuals stop foraging, take down their webs, and retreat before they can capitalize on this opportunity. Is the nutritional benefit of this forfeited prey significant compared to what they collect during the day, and if so, what potential cost might justify opting out of this potential gain? To investigate, sticky traps for prey collection and a camera array for recording predator activity were used at a local field site to survey what risks and rewards these spiders face throughout the 24-hour day. Spider activity in a lab environment and web captures in the field were also used to confirm behavioral patterns and nutrient uptake throughout the day. It was found that significant prey biomass is given up shortly after the time that spiders typically retreat, suggesting that the spiders truly forfeit this prey and do not simply retreat due to a gradual decrease in overall prey availability. Spiders reliably cease foraging in the early evening and show agitation throughout the night when not comfortably hidden, suggesting that significant extension of foraging behavior may be harshly punished. However, recorded predation events from the camera array were much rarer than anticipated, and no predation was confirmed in the evening. These results support the notion that these spiders’ circadian rhythms are shaped by factors other than prey availability, but more work is necessary to identify these factors