Observations of sand dune-obligate spider, Geolycosa wrighti, on Presque Isle State Park Final Report Matthew Foradori, PhD, Associate Professor Department of Biology and Health Services Edinboro University of Pennsylvania, 230 Scotland Road, Edinboro, PA 16412 Phone: (814) 732-1519 email: [email protected] Adam Hoke, Graduate Student Department of Biology and Health Sciences Edinboro University of Pennsylvania, 230 Scotland Road, Edinboro, PA 16412 Phone: (814) 720-1102 email: [email protected] Renee Foradori, MS, Adjunct Professor Department of Biology Gannon University, 109 University Square, Erie, PA 16541 Phone: (814) 403-7618 email: [email protected] Introduction Spiders from the Genus Geolycosa are somewhat rare arachnids endemic sandy habitats (Carrel, 2003). Geolycosa wrighti (Figure 1), a dune-obligate wolf spider, has been identified at Presque Isle State Park on two separate occasions (Truman, 1941; Buchkovich, unpublished). These burrowing wolf spiders are light brown on both the ventral cephalothorax and abdomen (Figure 1A). The ventral cephalothorax is a light brown color, usually becoming worn via sand abrasion, and ultimately resulting in hair loss, giving it a shiny appearance; the ventral abdomen is almost black (Bradley, 2013). According to Emerton (1912), G. wrighti is found in sandy environments along the Great Lakes region from the eastern end of Lake Erie near Buffalo west to Chicago, Illinois, and south to central Illinois, along the Illinois River. Its distribution along this range is sporadic and correlates with the presence of sand. Spiders in the genus Geolycosa are a unique group; like other wolf spiders, they can be vagile, yet predominantly exhibit a more sessile behavior. They frequently occur in habitat that has loose, sandy soil (Figure 2A) where they can burrow (Figure 2B) (Wallace, 1942). The burrow is constructed by excavating sand and wrapping it in small amounts of silk to produce a pellet. Each sand pellet is carried in their chelicerae to the opening of the burrow and deposited outside (Emerton, 1912). The upper part of the excavated burrow is lined with silk to prevent cave-ins (Nelson and Jackson, 2011); in some cases a turret is constructed at the end of the burrow (Wallace, 1942). G. wrighti have a minimal home range spending their entire life in the burrow or within a short distance of its opening. Females only leave their burrows to capture prey. Young males exhibit similar activity until they attain sexual maturity late in the season during September or October. Freshly molted, sexually mature males leave their burrows to actively seek out females for courtship and mating. Females lay fertilized eggs in late May then display maternal care by carrying the egg sac on their spinnerets. Care continues (Figure 3) after the spiderlings hatch until late June or early July, when the juveniles leave and construct their own burrows. The spiders overwinter in their burrows, and eventually reach sexually maturity the following September (Emerton, 1912). Both Skerl (1999) and Coddington et al. (1990) have suggested that G. wrighti be categorized as threatened or endangered. However, in an extensive review of threatened Pennsylvania invertebrates, three spiders were included while G. wrighti was omitted (Rawlins, 2 2007). As biodiversity is threatened by climate change, human development and contamination, it is of the utmost importance to monitor rare and threatened species in order to protect them and conserve their environments. Ecosystem conservation at unique places like Presque Isle State Park can only be enhanced by focusing some energy on the needs of these rare spiders. Ultimately, we would like them to be included in a review of threatened Pennsylvania invertebrates. Objectives The main objectives are: 1. Identify wolf spider burrows by sight, using sand pellets as potential burrow indications; collect spiders and confirm the presence of Geolycosa wrighti at Presque Isle State Park. 2. Survey these burrows for the presence of the burrowing spiders; monitoring the population throughout the year to identify population dynamics. Methods During the spring and summer of 2011 and 2012, we observed a population of Geolycosa wrighti on the eastern half of the Dead Pond Trail. The site was chosen after three periods of extensive observation, which started at the Thompson Circle and ended at the intersection with the B-Trail. Spiders were located by first finding the burrows; several of the spiders (Figure 1A, B) were positively identified to the species using resources by Ubick and coworkers (2005) and Wallace (1942). Spider burrow identification was performed by a bit of trial and error. Eventually, burrows were correctly determined by observing the presence of G. wrighti at the entrance. Ultimately, two sites were chosen immediately off of Dead Pond Trail. A 1.5 m2 perimeter was established around each of the group of burrows. Observations were performed on a weekly basis to determine specific burrow activity, which was defined as any visible proof that a spider currently inhabited a particular burrow. Each observation period lasted approximately 10 minutes. Results Geolycosa wrighti was initially observed on June 27th, 2011 on the most eastern part of the Dead Pond Trail named Site 1 (Figure 4, red dot). This outing provided excellent 3 observations of three adult G. wrighti. These burrowing spiders remained within close proximity to the opening of their respective burrows. This provided an excellent opportunity for photographic documentation (Figure 5C). Upon returning to Site 1 the following week (July 6th), however, all active burrows were absent. After careful analysis of the pictures taken from the first day, it was determined that one female G. wrighti was actively caring for young spiderlings. We now believe that the adult females sealed off the burrow entrance to either (1) protect the spiderlings, as suggested by Aisenberg et al. (2011), or (2) force the spiderlings to disperse by restricting access. The following week (July 13th), two burrows were again found at Site 1, one of which was identified as active. Site 1 was an exposed part of the trail, and saw constant traffic. Animal and human footprints were always plentiful during each observation period; sometimes SUV tracks were evident. In spite of this, we decided to keep monitoring Site 1, but we also wanted to add a second, low traffic area as well. Approximately 40-50 meters west on the Dead Pond Trail, a second field site (Figure 4, blue dot), Site 2, was established around a population of five juvenile G. wrighti burrows that were located within a radius of approximately 30 cm from each other (Figure 6). After setting up a 1.5 m2 field site, (Figure 6), we positively identified six burrows and after a ten minute observation period on this site it was determined that 4 of the 6 burrows could be classified as “Active”. In one instance, we recorded juvenile feeding behavior at the Site 2 (Figure 5A, B). Over the course of the next 3 months weekly observations were conducted at both sites along the Dead Pond Trail, to monitor any change in the spider populations. Activity continued at Site 1 throughout our research. Most notably, there was a large increase in the population of juvenile G. wrighti in the general area around Site 2 in the middle of September. The activity of spiders at both field sites gradually diminished both in abandoned and active burrows with the onset of fall. Juvenile spiders seal off the entrance to the burrow in order to overwinter (Emerton, 1912). Discussion Geolycosa wrighti, a dune-obligate wolf spider is an uncommon arachnid in Pennsylvania. It has been found at Presque Isle State Park, (Truman, 1941) and exhibits a patchy distribution across the sand dunes. The spider appears to have a centrally located distribution in 4 the dunes and scrub of Presque Isle; our efforts to locate this species on the exposed west-facing beaches and shoreline found none. This report focuses on observations of a population of G. wrighti located on the Dead Pond Trail. While described as being predominantly sessile (Wallace, 1942), we observed fluctuations in burrow activity, placement, and construction from week to week and month to month. The laborious construction of a burrow is not an indication that the spider is coupled to that location. Disturbances to the burrow site, natural or man-made, no matter how small, appear to be enough to cause the spider to leave and construct a burrow in another location. What constituted a good site (substrate selection) remains to be determined. Prey was abundant in our observations at both Site 1 and Site 2, and spiders were observed in the process of either hunting for or capturing prey during every observation period. There was a brief time at the end of June where the number of active burrows observed dropped precipitously. The reason was not immediately clear at the time, but in retrospect, it was during a brooding period by female G. wrighti. Each female seals off the burrow from during a period of time in order for the spiderling to develop. The female is exhibits maternal care by being ‘tolerant’ toward the spiderlings for this brief period of time (Miller, 1989). By the middle of July, the number of active burrows rebounded to those in early June. Photographic evidence (Figure 3) indicates that even after the burrows were reopened, maternal care could be exhibited. There appears to be little impact on G. wrighti by foot traffic and vehicle traffic on the Dead Pond Trail (see recommendations below). That being said, G. wrighti has been omitted from an extensive list of threatened or endangered Pennsylvania invertebrates created by Rawlins (2007). This is troubling considering multiple researchers feel that these spiders should be classified as such (Skerl, 1999; Coddington et al., 1990).