Survey
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INTRODUCTION Georgia’s historic conservation and management efforts have resulted in a range of ecosystems rich in endemic and charismatic species. Georgia’s barrier islands are touted as the crown jewels of Georgia’s coast due to their status as the least disturbed coast on the eastern seaboard (http://www.georgiawildlife.com/node/1060). These dynamic, protected coastal ecosystems serve as nurseries for a host of beloved and increasingly threatened species. New challenges continue to emerge with a key issue being the introduction and assimilation of aggressive ant species. Red imported fire ants, Solenopsis invicta, Black imported fire ants, S. richteri, their hybrid, and the tropical fire ant Solenopsis geminata can be found throughout the state (Gardner et al. 2008) (Wetterer 2011). Meanwhile big-headed ants, Pheidole megacephala, and little fire ants, Wasmannia auropunctata are both present on the Florida coast (Wetterer 2012, Wetterer 2013) and could easily move north into Georgia’s barrier islands in a similar fashion to the tawny crazy ant Nylanderia fulva, which was first reported in Georgia in 2013 (Gochnour 2015). The above species are known to negatively affect or outright depredate a plethora of species, such as shrub nesting songbirds, small mammals, butterflies, shore birds and both marine and terrestrial reptiles (Conner et al. 2010, Diffie et al. 2010, Wauters et al. 2014, Long et al. 2015, Dziadzio et al. 2016). When species are not out-right depredated by ants, vertebrate behavior can be altered by the ants presence (Langkilde 2009). Notably, on Georgia’s barrier islands nesting Loggerhead sea turtles, shore birds, and endemic herpetofauna are at risk of negative impacts from aggressive, predatory ants. Additionally, native ant species are likely to have evolved to take advantage of the resources historical present among the barrier islands. While other issues may be larger threats to these species, every successful nest protected from depredation increases the health of already fragile populations. Similar to the species richness found in Georgia’s vertebrate fauna, Georgia has an abundant and diverse ant assemblage (Ipser et al. 2004) yet the barrier islands are understudied in regards to ants. Native ants are also negatively impacted by invasive ant species, with invasive species often outcompeting or even extirpating local ant fauna. The difficulty of sampling for small cryptic animals on sand as well as their relative scarcity has left open a natural history niche with a wide array of research possibilities. While invasive ants have been shown to depredate sea turtle eggs and hatchlings (Allen et al. 2001, Parris et al. 2002, Wetterer et al. 2007), very little is published regarding ant depredation of sea turtles in Georgia, with the most recent article on the matter published nearly 20 years ago (Moulis 1997). We propose a 2-year research project involving a large-scale survey of the ground-inhabiting ant assemblage on Georgia’s barrier islands. This effort will involve collaborations with teams throughout the Georgia coast who will be collecting ants observed in the process of depredating sea turtle nests and hatchlings. These surveys will broaden our knowledge of ant diversity and abundance on Georgia’s barrier islands while providing confirmation of which ant species are affecting beach-nesting vertebrates and document the current situation. In addition the survey will also help monitor for the presence of potential invasives such as W. auropunctata, P. megacephala, and, N. fulva. MATERIALS AND METHODS Collaborators throughout the state will be collecting ants encountered depredating sea turtle nests and hatchlings. Ants will be collected in 120 mL (4oz) specimen cups, frozen, and stored. Samples will be identified to species once in Athens. The detailed survey entails traps constructed of PVC tubing encapsulating a bait (combination of peanut butter, tuna fish, or hot dog) inside two nested tubes, which can be opened/closed by rotating the outer sleeve. The traps have holes large enough for ants to enter but prevent larger animals from gaining access. Importantly, the baits will be deployed for a 1-2 hour window then promptly collected, minimizing the potential for recruitment of vertebrate pests. Twist and seal bait trap design A 1.27 cm (1/2“) long ring was cut of 3.175 cm (1-1/4“) diameter PVC and affixed with Oatey heavy duty clear PVC cement inside a 1-1/4“ slip cap. A 2.54 cm (1”) diameter PVC pipe cut to 16.5cm (6.5”) in length was then inserted into the same slip cap, guided by the ring, and affixed to the slip cap with PVC cement. A 3.175 cm (1- 1/4“) PVC pipe cut to 15.24 cm (6”) in length was inserted into the dried slip cap. A series of three holes spaced roughly 3.81 cm (1.5”) apart along the length of the apparatus were drilled into both pipe lengths simultaneously using a 3/16 drill bit. A parallel set of three holes was then drilled, spaced roughly 5 cm (2”) in circumference away from the first holes. Finally, a second slip cap was attached to the apparatus, but not cemented to provide an accessible opening. Figure 1: Slip cap and ring Figure 2: Both pipes can be manipulated independently Baits will be deployed for 2 hours, collected, processed, and then redeployed in the same plot. Each time portion of a sequential time-series, 8am-10am, 10am-12pm, etc., will be sampled until a 24 hour cycle is completed in the plot to asses which ant species forage along the dunes at which time of day. Figure 3: One slip cap remains uncemented and serves as the bait reservoir A plot will be considered a replicate and entail 5 traps deployed every 10 meters along a transect perpendicular to the tide line from the inland dune edge to the seaward primary dune front. 21 traps will also be deployed along the dune front parallel to the tide line until 200 meters of beach length have been covered. 4 secondary transects will be placed every 50 meters. A rough plot design can be seen below, consisting of 21 traps along the dune front and 12 within the primary dune for 33 total traps. Initial Transect Dune Front Inter-dune edge Figure 2: Bait trap plot design. Each star represents a bait trap. This hypothetical design would be modified based on dune topography and delicacy in each area. Pitfall traps would be placed at both ends of the five transects Sampling will be intentionally biased towards the dune front because sea turtle nest depredation is possibly correlated to nest proximity to the dune front and ants are known to nest in dunes but not open sand of the upper or intertidal beach. As such, foraging ants of greatest interest to this study are those which are active along the dune front. However, occasional samples throughout the dune will ensure that we are performing due diligence in our sampling of scavenging ant species present. Intermittently, covered pitfall traps will be deployed alongside the baited traps. Each replicate would have 12 rounds of timed baits deployed to survey an entire 24 hour period to ensure both night and day foragers are sampled for. Five plot replicates will be attempted during the course of the survey season and dispersed throughout the island’s length. Each plot site will be selected based on historical sea turtle nest depredation data and input from island naturalists. Extreme care will be taken to ensure native organisms and ecosystems are not unduly disturbed. No baits or excess materials will be left on the beach or near vulnerable sites to attract unwanted scavengers. Ten pitfall traps will be placed alongside the bait traps on the perimeter of the plot. The pitfall will be 7.62 cm (3”) diameter PVC pipe buried to a depth of 0.5 m; analogous to the depth of a loggerhead nest. The tops of the pitfalls would be covered to prevent both accidental capture of unwanted organisms and sand inundation. The length of the pitfall trap would be perforated with small holes drilled with a 3/16 bit starting just beneath the cap, at 5 cm in depth, and spaced every 10 cm thereafter so that subterranean foragers have access to the trap. The trap will have no bait and a cup at the base containing a vertebrate safe collecting solution, propylene glycol. Pitfalls would be deployed at the beginning of a survey and checked daily thereafter and removed at the end of each two week survey period. The burial of the pitfall will have the added benefit of causing disturbance similar to turtle nest deposition or hatchling emergence, another possible trigger for ant recruitment. Plot placement of the traps would be selected based on historical ant depredation data provided by Georgia Department of Natural Resources and the Georgia Sea Turtle Cooperative, as well as input from management and research professionals on site. At least 2 sites will be sampled per survey trip and trips will be undertaken until at least 5 plots have been sampled. Precautions Extreme caution will be undertaken to ensure no nesting birds, turtles, or other wildlife are disturbed, and areas where such nesting is underway will be excluded from the survey plots. Care will be taken during trap deposition and collection to ensure native organisms and ecosystems are not unduly disturbed. No baits or excess materials will be left on the beach or near vulnerable sites to attract unwanted scavengers. Additionally, the traps are small, white, and discreet. Baited traps will only be ephemerally present on the beach as they are timed and then immediately collected. Pitfall traps will be buried and mostly out of sight ensuring a minimum degree of both physical and visual disturbance. The traps use propylene glycol, which is neither volatile nor sweet, and non-toxic to vertebrates. This will prevent unwanted predator attraction while the covered design prevents all organisms larger than a 3/16 drill bit from entering the trap. Survey Project Goals 1. Document the current species composition and relative abundance of the ground nesting ant community by collecting both predacious ants via baits and subterranean ants via pitfall traps. 2. Determine the foraging time and efficiency of scavenging ants by baiting through a 24 hour time series. 3. Compare species observed in our survey to species collected by turtle monitoring field teams throughout the state to identify which species of ants are interacting with beach nesting vertebrates. Future Research Goals While it is not possible to guarantee at this time, once ant specimens have been collected, they could be analyzed in the future for a suite of biocontrol pathogens. Parasitic flies, microsporidia, and species specific viruses have all been identified as possible biocontrol agents for problematic ants and leave distinct traces on parasitized ants. Already present in some ant communities in north Florida (Valles et al. 2010) and Georgia (Gardner et al. 2013), the presence or absence of biocontrol agents along the coast would inform future researchers as to their potential management utility. These current and future project goals would coalesce to furthering our scientific understanding of a unique system by better documenting the species assemblage and abundance of ground nesting ants. Further, by determining their presence, foraging behavior, and associates, an optimal control model can be generated to manage problematic species through a combination of biocontrol agents and targeted bait treatments. Once such a plan has been made, local island agents would have a wellinformed ability to respond to ant issues appropriately and effectively with minimum impact to other important species. Works Cited Allen, C. R., E. A. Forys, K. G. Rice, and D. P. Wojcik. 2001. Effects of fire ants (Hymenoptera : Formicidae) on hatching turtles and prevalence of fire ants on sea turtle nesting beaches in Florida. Fla. Entomol. 84: 250-253. Conner, L. M., J. C. Rutledge, and L. L. Smith. 2010. Effects of Mesopredators on Nest Survival of ShrubNesting Songbirds. J. Wildl. Manage. 74: 73-80. Diffie, S., J. Miller, and K. Murray. 2010. Laboratory Observations of Red Imported Fire Ant (Hymenoptera: Formicidae) Predation on Reptilian and Avian Eggs. J. Herpetol. 44: 294-296. Dziadzio, M. C., A. K. Long, L. L. Smith, R. B. Chandler, and S. B. Castleberry. 2016. Presence of the red imported fire ant at gopher tortoise nests. Wildl. Soc. Bull. 40: 202-206. Gardner, W. A., H. B. Peeler, and S. K. Diffie. 2013. Occurrence of Phorid Fly (Diptera: Phoridae) Parasitoids of Imported Fire Ants (Hymenoptera: Formicidae) in Georgia. J. Entomol. Sci. 48: 243-250. Gardner, W. A., S. Diffie, R. K. V. Meer, and M. A. Brinkman. 2008. Distribution of the fire ant (Hymenoptera : Formicidae) hybrid in Georgia. J. Entomol. Sci. 43: 133-137. Gochnour, B. M., Joe A.; Suiter, Daniel R. 2015. The Tawny Crazy Ant, Nylanderia fulva, in Georgia. In U. o. Georgia [ed.]. UGA-CAES Extension. Ipser, R. M., M. A. Brinkman, W. A. Gardner, and H. B. Peeler. 2004. A survey of ground-dwelling ants (Hymenoptera : Formicidae) in Georgia. Fla. Entomol. 87: 253-260. Langkilde, T. 2009. Invasive fire ants alter behavior and morphology of native lizards. Ecology 90: 208217. Long, A. K., L. M. Conner, L. L. Smith, and R. A. McCleery. 2015. Effects of an invasive ant and native predators on cotton rat recruitment and survival. J. Mammal. 96: 1135-1141. Moulis, R. A. 1997. Predation by the imported fire ant (Solenopsis invicta) on loggerhead seat turtle (Caretta caretta) nests on Wassaw National Wildlife Refuge, Georgia. Chelonian Conservation and Biology 2: 433-436. Parris, L. B., M. M. Lamont, and R. R. Carthy. 2002. Increased incidence of red imported fire ant (Hymenoptera : Formicidae) presence inloggerhead sea turtle (Testudines : Cheloniidae) nests and observations of hatchling mortality. Fla. Entomol. 85: 514-517. Valles, S. M., D. H. Oi, and S. D. Porter. 2010. Seasonal variation and the co-occurrence of four pathogens and a group of parasites among monogyne and polygyne fire ant colonies. Biol. Control 54: 342-348. Wauters, N., W. Dekoninck, H. W. Herrera, and D. Fournier. 2014. Distribution, behavioral dominance and potential impacts on endemic fauna of tropical fire ant Solenopsis geminata (Fabricius, 1804) (Hymenoptera: Formicidae: Myrmicinae) in the Galapagos archipelago. Pan-Pacific Entomol. 90: 205-220. Wetterer, J. K. 2011. Worldwide spread of the tropical fire ant, Solenopsis geminata (Hymenoptera: Formicidae). Myrmecol. News 14: 21-35. Wetterer, J. K. 2012. Worldwide spread of the African big-headed ant, Pheidole megacephala (Hymenoptera: Formicidae). Myrmecol. News 17: 51-62. Wetterer, J. K. 2013. Worldwide spread of the little fire ant, Wasmannia auropunctata (Hymenoptera: Formicidae). Terrestrial Arthropod Reviews 6: 173-184. Wetterer, J. K., L. D. Wood, C. Johnson, H. Krahe, and S. Fitchett. 2007. Predaceous ants, beach replenishment, and nest placement by sea turtles. Environ. Entomol. 36: 1084-1091.