Dr. Linda Rayor Research Interests:
Evolution of sociality must involve adaptive benefits to offset costs of living with competitors, especially among potentially cannibalistic predators. I am particularly interested in the trade-offs that obligate predators make to live in social groups. For example, group members may benefit by sharing prey or evade other predators more effectively in the group, but remaining in the group may also reduce their own reproduction. Understanding the factors that influence the evolution of social behavior and how social groups function are central issues in behavioral ecology today.
My research interests are in two primary areas:
(1) Patterns of cooperation and conflict in an extremely atypical social huntsman spider, Delena cancerides [Araneae: Sparassidae], with comparisons to closely related solitary huntsman spiders.
(2) Patterns of social communication and exploration in social whip spiders (Arachnida: Order Amblypygi).
Adaptations for Group-Living in Social Huntsman Spiders:
The primary research in my laboratory is on the social behavior, mother-offspring dynamics, in the endemic Australian huntsman spider, Delena cancerides (Sparassidae). Delena were the spider stars of the 'Arachnophobia'!
Complex and long-lasting social interactions among family or communal groups of arachnids (spiders, scorpions, amblypygids, harvestmen, pseudoscorpions, etc.) is extremely rare (Rayor & Taylor 2006), although transient maternal defense of eggs and newly emerged young occurs sporadically throughout the arachnids. Social behavior beyond transient maternal care is only found in 55 spider species (Whitehouse & Lubin 2005) and 17 non-spider arachnids (Rayor & Taylor 2006), or something less than 0.01% of all known arachnid species. Other than the Acarines (mites and ticks), all arachnids are obligate predators which apparently results in steep barriers to group-living. Although rare, sociality is found in 13 diverse, taxonomically unrelated spider families (Aviles 1997, Uetz & Heiber 1997, Lubin & Bilde 2007). Yet across the taxonomic spectrum, all but the social huntsman species share key behavioral traits. All live in web-based societies, even when other members of the family do not build prey capture webs (Aviles 1997). The unequivocal advantage of group-living in social spiders is enhanced prey capture success through shared use of webs and cooperative prey capture (Whitehouse & Lubin 2005). Sociality in spiders is extremely rare.
Delena canerides is considered to be the most unusual of the known social spiders with important characteristics that differ from those of all other social spiders. Unlike all other social spiders, they do not live in webs, are extremely aggressive to non-colony mates, have a 1:1 sex ratio, and are highly outbred with unusual chromosomal races (Rowell & Aviles 1995). Delena simply do not fit any current understanding of spider sociality. Delena are large non-web building spiders that live under the bark of dead trees in year-round colonies of up to 300 individuals. The narrow bark-covered retreats are relatively rare and can readily be defended from intruders, unlike the relatively open web-based colonies of other social spider species. The social demographics of Delena vary along a continuum from a single breeding female with multiple clutches of offspring to the substantially more complex dynamics of multiple adult social groups. Although they lack communal webs that facilitate cooperative prey capture and communication, Delena share prey and interact frequently with a diverse behavioral repertoire. Delena exhibit important components of conflict and cooperation more typical of eusocial insects than social spiders, including aggression toward non colony-mates and competition between reproductive females. Even courtship and mating is unusual in these spiders, as these huntsmen spiders mate for hours, with many partners, and males may simultaneously attempt to copulate with females! Because of the confluence of unusual behavioral and genetic traits, Delena cancerides are a wonderful system to test theories of social evolution and group living.
Projects on Delena cancerides in my laboratory include:
- A comparison of courtship, mother-offspring interactions, prey sharing, and growth rates in Delena with those seen in solitary huntsmen spider species.
- Studying the social dynamics in colonies with different social demographics.
- Examining the role of prey availability and retreat size on social dynamics.
- Consequences of sociality on courtship and mating patterns in Delena
- Experiments and simulation models to determine which factors affect individuals' decisions to remain with the social group or depart from the natal colony.
- A determination of genetic relationships within Delena colonies, in collaboration with Dr. David Rowell, Australian National University.
- Investigate factors involved in kin recognition and aggression between non-colony mates.
Social Behavior in Amblypygids
Amblypygids or whip spiders are close relative of spiders (Arachnida: Amblypygi). Like spiders and most other arachnids, the amblypygids have the same basic body structure: two main body parts (cephalothorax and abdomen), eight legs, and palps on either side of their mouth. But the amblypygids have palps and first legs very different from the spiders. The amblypygids have strong, spiny raptorial palps that are used to capture prey and their extremely long, flexible first legs act like antennae to pick up sensory information from their surroundings. Amblypygids lives are centered on the sensory information they acquire through their whips. An amblypygid’s whips are in constant movement exploring their environment.
Until recently, amblypygids have been considered to be completely solitary and highly aggressive to conspecifics. Because of my long-term interest in how early mother-offspring dynamics affect patterns of social organization, I began watching the interactions between youngsters and their mother in two amblypygid species. Completely to my surprise, I discovered that (at least in captivity) these species have quite complex communicative and social interactions that last until the animals become sexually dimorphic around 1-year of age!
Research on amblypygids in my laboratory has focused on amblypygid social dynamics, kin recognition, and ontogenetic changes in behavior. We have found that in Damon diadema (Family Phrynichidae) there is prolonged association and tolerance between mothers and their offspring, active aggregation, frequent amicable tactile interactions, and kin recognition. In Rayor & Taylor (2006), I coined a term for this long-term, complex, and interactive association between mothers and their offspring as ‘prolonged subsocial’. Immature amblypygids and their mothers form large interactive groups that are in constant tactile (whip) contact with one another. Young D. diadema remain closely associated and highly interactive until they reach sexual maturity at approximately 12 - 15 months, at which time they avoid interaction with one another except when coming together for courtship. Patterns of grouping and proximity change gradually as the amblypygids mature. Agonistic interactions among siblings are mild and infrequent prior to sexual maturity. Young siblings (4 to 6 months) interact constantly and are significantly more amicable than interactions among subadult siblings (10 to 11 months) or within mixed groups of unrelated animals. Agonistic behavior is significantly higher among unfamiliar individuals than among sibling groups. When experimentally disturbed or moved into an unfamiliar environment, young amblypygids immediately aggregate with one another and move closer to their mother. Exploring amblypygid communication and social dynamics is the current focus of this system in my laboratory.
If this work is of interest to you, please check out the following papers:
Linda S. Rayor. 2007. Family Ties: Unexpected social behavior in an improbable arachnid, the whip spiders. Natural History Magazine. 116: 38-44.
L.S. Rayor & Taylor, Lisa. 2006. Social behavior in amblypygids, and a reassessment of arachnid social patterns. Journal of Arachnology 34: 399-421
Walsh, Rachel & L.S. Rayor. 2008. Kin discrimination in the amblypygid, Damon diadema). Journal of Arachnology 36:00 – 00 (8 pages)
Graduate Student: Eric C. Yip
My dissertation examines the evolution of sociality in the huntsman spider, Delena cancerides. These spiders form mother-offspring groups under exfoliating bark and do not build capture webs like the majority of other social spiders. Many of the benefits of group-living proposed for spiders, such as the cooperative capture of large prey, depend on the presence of a web. I examine the costs and benefits of group-living in this webless spider to examine how different selective pressures may have led to sociality in this species. My project has combined field work in Australia and laboratory studies at Cornell University to examine foraging patterns, predator defense, nestmate recognition, inter-colony migration rates and genetic relatedness in this species. Currently, I am examining female inheritance of the natal retreat and competition for available retreats to further examine constraints on dispersal in Delena cancerides.
Funding Sources: Sage Fellowship – Cornell University; Australia-US Fulbright Fellowship 2006-2007; NSF GRFP.
Undergraduate Members of the Lab Currently and Some Former Members of the Lab:
CURRENT UNDERGRADUATES IN THE LABORATORY:
Jenna DeNicola - Honors Project - Comparative social behavior in Australian huntsman spiders. Previous projects have included a collaborative project on kin recognition patterns in amblypygids and assisting with Ariel Zimmerman's Honors project involving growth and survival of several huntsman species in solitary and group-living situations. Jenna is in charge of animal care in the lab and a prolific tarantula collector.
Chung 'Albert' Chiu - Honors Project - Running speed and metabolic rates in Australian huntsman spiders. Albert has previously assisted on the project on survival and growth rates in solitary and group situations. Former animal care assistant.
Anthony Auletta - Project - How many Delena cancerides spiders really share prey at a time? Comparing color changes and sharing patterns in social spiders. Anthony was a collaborator on the kin recognition in amblypygid project. Anthony has made outstanding signs for the Arthropod Zoo at Insectapalooza for the last 2 years. Anthony is a scorpion afficianado.
SOME OF THE FORMER MEMBERS OF THE LABORATORY (WHO HAVE REMAINED IN ACADEMICS);
Ariel Zimmerman - Honors Project: Assessing the costs of group living: Comparing metabolic physiology and growth in social and solitary spiders. Winner of the Paul Scheur Award for Academic Excellence and Research and one of ‘25-Most Impressive Seniors’ at Cornell. Ariel is now pursuing graduate work at the University of Florida in Dr. Jamie Gillooly's lab with the assistance of an NSF GRFP.
Mike Avery – Honors Project: Investigations into colony identity in a social spider: Does Delena cancerides utilize chemical cues to distinguish between kin and non-kin? Mike is now pursuing graduate work at the University of Pennsylvania on effects of global warming on invertebrate and vertebrate fauna in Greenland.
Claire Rittschof – Dominance and conflict in Delena colonies. Currently at the University of Florida working on the Golden Orb weaver, Nephila clavipes, in Dr. Jane Brockmann’s lab.
Frank Castelli – Early warning of prey and predators in amblypgyids through use of their whip in amblypygids. Frank is completing a masters degree on social vole genetic relationships at the University of Miami – Ohio. Frank has been the Youth Coordinator on three Cornell Adult University tours to Tanzania and Panama with Dr. Rayor.
Rachel Walsh – Honors Project: Social Dynamics in a Whip Spider (Order Amblypygi, Family Phrynichidae: Damon diadema) and an Unusual Huntsman Spider (Sparassidae: Delena cancerides). Cornell Presidential Research Scholar. Rachel is studying tamarin monkeys as a graduate student at the University of California – Berkeley in Dr. Eileen Lacey’s lab.
Lisa Taylor – Honors Thesis: Social Behavior, Aggregation, and Mother-Offspring Interactions in two species of captive Tailless Whip Scorpions (Order Amblypygi: Phrynus marginemaculata and Damon diadema). Lisa is exploring how color patterns affect sexual selection in jumping spiders at the University of Arizona in Dr. Kevin McGraw’s lab.