Raymond R. Carthy

INCREASED INCIDENCE OF RED IMPORTED FIRE ANT (HYMENOPTERA: FORMICIDAE) PRESENCE IN LOGGERHEAD SEA TURTLE (TESTUDINES: CHELONIIDAE) NESTS AND OBSERVATIONS OF HATCHLING MORTALITY

Red imported fire ants, Solenopsis invicta Buren, were introduced to North America in the 1930s (Buren 1972). Since their introduction, fire ant distribution and abundance has continued to increase dramatically. Fire ants have infested more than one hundred million hectares and expanded their range throughout most of the southeastern United States (Callcott & Collins 1996). Fire ants are an omnivorous and opportunistic species, and are often aggressive predators and competitors of native species. Fire ants have the potential to negatively affect vertebrates (Allen et al. 1994). Oviparous species may be especially vulnerable to fire ant predation, particularly ground nesting birds and reptiles (Allen et al. 1994, Allen et al. 1997, Tuberville et al. 2000, Wojcik et al. 2001). Observations of fire ant predation on amphibian and reptilian eggs and hatchlings have been reported for numerous species (Landers et al. 1980, Mount et al. 1981, Freed & Neitman 1988, Montgomery 1996, Allen et al. 1997, Buhlmann & Coffman 2001). The occurrence of red imported fire ants in green sea turtle, Chelonia mydas, and loggerhead sea turtle, Caretta caretta, nests have been documented (Wilmers et al. 1996, Moulis 1997), however few researchers have been able to document observations of hatchling mortality due to fire ants. Hatching sea turtles may be particularly vulnerable to fire ant predation. Sea turtles are oviparous, subterranean nesting species. Prior to hatchling emergence from the nest, newly hatched turtles remain in the ground for up to seven days (Lohmann et al. 1997), during which they may be susceptible to injury from fire ants. In addition, fire ants primarily feed on high protein resources during brood production in late spring, which coincides with the start of sea turtle nesting season. In this paper, we provide observations of predation by fire ants on loggerhead sea turtle hatchlings on Cape San Blas, Florida. Cape San Blas, a coastal barrier island along the Northern Gulf of Mexico, supports the largest density of nesting loggerhead turtles in northwest Florida (Fig. 1). Encalada et al. (1998) identified this group of nesting loggerhead sea turtles as genetically distinct from other nesting populations in southeastern United States. Surveys for nesting sea turtles have been conducted every year since 1994 along Eglin Air Force Base property on Cape San Blas by foot and on ATV. Two surveyors conducted daily monitoring surveys of the 5-km area from 6:00 am to 10:00 am every morning from May 15 to August 15. From August 15 to October 31, nests were observed daily for signs of hatchling emergence or depredation. Nest inventories were conducted 72 h after first emergence or after 85 days of incubation, and number of hatched, unhatched, and depredated eggs was recorded. Red imported fire ant presence was not recorded in sea turtle nests on Cape San Blas before 1995 (Table 1). In 1995, fire ants were observed on one of 60 loggerhead sea turtle nests; however, fire ant induced hatchling mortality was not documented. In 1996, fire ant presence was not recorded on any of the 25 loggerhead sea turtle nests. Fire ants were observed again in 1997 on 14 of 54 loggerhead nests (25.9%). Hatchling mortality was witnessed at two of the 54 nests (3.7%). Upon excavation of one nest, fire ants were observed consuming one sea turtle hatchling that had cracked (pipped) the egg shell, entering and stinging a live turtle within a second pipped egg, and stinging a third hatchling. In the second nest, fire ants were observed consuming an undetermined number of pipped eggs, and skeletonizing five hatchlings before emergence from the nest. In 1998, fire ants were observed on 10 of 57 nests (17.5%). Fire ant depredation resulted in mortality of 23 hatchlings, combined in three of the 57 nests (5.3%). Hatchling mortality was not recorded in the remaining seven fire ant infested nests. In 1998, surveyors observed one hatchling being consumed by fire ants near the nest surface. Upon excavation of the nest, an additional twenty dead hatchlings and one live hatchling were observed covered with fire ants. Fifteen live hatchlings were removed from the infested nest and released. Injures observed on numerous live hatchlings included blinding due to removal of eyes and wounds on head and flippers due to necrotizing fire ant stings. All fire ant induced hatchling mortalities were observed in nests left to incubate in-situ along the North beach, not in the nests relocated to East beach.

Comparison of methods for estimating abundance of gopher tortoises

Estimates of abundance of threatened and endangered species are crucial for monitoring population status and recovery progress. For most wildlife species, multiple abundance estimation methods are available and the choice of method should depend on cost and efficacy. We field-tested the cost and efficacy of line transect, total count, sample count, and double observer methods for estimating abundance of gopher tortoise (Gopherus polyphemus) burrows in two habitats that differed in vegetation density (sparse and dense) at the Ordway-Swisher Biological Station in north-central Florida. In the dense vegetation stratum, density of burrows estimated using the line transect method (8.58 ± 0.94 burrows ha−1) was lower than that obtained from the total count method (11.33 burrows ha−1). In the sparse vegetation stratum, estimated burrow density using the line transect method (11.32 ± 1.19 burrows ha−1) was closer to the burrow density obtained from the total count method (13.00 burrows ha−1). Density of burrows estimated using the double observer method was identical to that obtained from the total count method in dense vegetation stratum, but slightly greater than that obtained from the total count method in sparse vegetation stratum. Density of burrows estimated using the sample count method varied widely depending on the proportion of plots sampled. The cost of sampling as well as estimates of burrow density varied with habitat type. The line transect method was the least costly of the methods, and we were able to sample a larger effective area with the same effort. Using burrow cameras and patch occupancy modeling approach, we also estimated the probability of burrow occupancy by gopher tortoises (active: 0.50 ± 0.09; inactive: 0.04 ± 0.04), and used these values to estimate abundance of gopher tortoises. Using estimates of burrow abundance based on the line transect method, density of gopher tortoises was 2.75 ± 0.74 ha−1 in the sparse vegetation stratum. We recommend that gopher tortoise monitoring programs use rigorous methods for estimating burrow abundance (e.g., line transect methods) and the probability of burrow occupancy by gopher tortoises (e.g., patch occupancy modeling approach).

Declining Reproductive Parameters Highlight Conservation Needs of Loggerhead Turtles (Caretta caretta) in the Northern Gulf of Mexico

Abstract Marine turtles in the Gulf of Mexico are at risk due to many anthropogenic threats including habitat degradation, commercial fishing, and petroleum activities. The severity of this risk was made apparent in 2010 with the occurrence of the Deepwater Horizon oil spill. The objectives of this study were to assess long-term trends in abundance and reproductive parameters for this genetically distinct nesting group. From 1994 to 2010, morning surveys were conducted along 3 beaches on the St Joseph Peninsula, Florida, including within our primary study site on Cape San Blas. Nest abundance on all 3 beaches declined by at least 47% (p < 0.01). Mean nesting success on Cape San Blas was 40% and also declined (p  =  0.002). Mean clutch size was 108 and mean emergence success was 58%. Throughout the study there were no changes in clutch size and emergence success. We found that nesting characteristics for the northern Gulf of Mexico subpopulation appear similar to those from other loggerhead turtle nesting groups in the southeastern United States in some ways, such as emergence success, timing of peak nesting, and incubation duration and different in other ways such as nesting success. Variation in some of the parameters may indicate turtles among the different nesting groups experience different environmental conditions. The severity of declines in nest abundance and the low nesting success reported for this small subpopulation suggest potentially serious consequences for this nesting group.

Response of Nesting Sea Turtles to Barrier Island Dynamics

ABSTRACT Although barrier island beaches provide important nesting habitat for sea turtles, they are constantly changing. To determine how nesting sea turtles have responded to this dynamic environment, we assessed: 1) wind, current, and tidal patterns and changes in beach profiles, 2) sea turtle nesting patterns, and 3) success of turtle nests deposited along 5 km of beach on Cape San Blas, Florida, an extremely dynamic barrier beach in northwest Florida. From 1998 to 2000, nesting turtles were tagged, nests were monitored, and hatching success was determined. Throughout this study, West beach lost ∼ 5 m of sand while East beach gained ∼ 4 m; however 61% of nests were deposited on West beach and 39% on East beach. Hatchling emergence success did not differ between beaches. Wind direction influenced current direction and sand movement and affected the number of nests deposited along East beach but not on West beach. Nearly all nests (98%) oviposited on both beaches were deposited during a rising tide. Although West beach is narrow and eroding, the steep slope may enable nesting turtles to expend less energy to reach higher nesting sites while still providing successful nests. Nesting on a rising tide and using offshore currents during the internesting period may assist this effort.

Winter Diets of Immature Green Turtles ( Chelonia mydas ) on a Northern Feeding Ground: Integrating Stomach Contents and Stable Isotope Analyses

The foraging ecology and diet of the green turtle, Chelonia mydas, remain understudied, particularly in peripheral areas of its distribution. We assessed the diet of an aggregation of juvenile green turtles at the northern edge of its range during winter months using two approaches. Stomach content analyses provide a single time sample, and stable isotope analyses integrate diet over a several-month period. We evaluated diet consistency in prey choice over time by comparing the results of these two approaches. We examined stomach contents from 43 juvenile green turtles that died during cold stunning events in St. Joseph Bay, Florida, in 2008 and 2011. Stomach contents were evaluated for volume, dry mass, percent frequency of occurrence, and index of relative importance of individual diet items. Juvenile green turtles were omnivorous, feeding primarily on seagrasses and tunicates. Diet characterizations from stomach contents differed from those based on stable isotope analyses, indicating the turtles are not feeding consistently during winter months. Evaluation of diets during warm months is needed.

Growth rates of wild green turtles, Chelonia mydas, at a temperate foraging habitat in the northern Gulf of Mexico: assessing short‐term effects of cold‐stunning on growth

There are multiple factors that may determine individual and population growth rates and understanding the impact of extrinsic factors, such as temperature, is important for successful recovery plan stock assessment and modelling. In January 2001 and January 2003, cold‐stunning events occurred along the northern Gulf of Mexico, in St Joseph Bay, Florida. In this study we examine the short‐term effects of decreased water temperatures and repeated cold‐stunning events on the growth of juvenile green turtles in northwest Florida. There were no significant effects of number of cold‐stunning events on growth, although turtles stunned twice tended to grow slower than non‐stunned turtles. This is the first study to provide information on the growth rates of green turtles in the northern Gulf of Mexico and it is the first examination of the effects of cold‐stunning on growth in any sea turtle population.

Changing taste preferences, market demands and traditions in Pearl Lagoon, Nicaragua: A community reliant on green turtles for income and nutrition

Caribbean Nicaragua has its own cultural logic that helps to explain the eating habits of indigenous communities that rely on sea turtle meat for nutrition and prefer its taste to that of other available meats. Nutritional costs and benefi ts form a fundamental part of this reliance, yet there are ecological, economic, cultural, and other factors that may be just as if not more important than the nutritional value of turtle meat. Caribbean Nicaraguans have legally harvested green turtles (Chelonia mydas) for more than 400 years, and continue to rely on the species as an inexpensive and tasty source of protein and income. From 1967 to 1977, green turtles were harvested for both local and foreign consumption, including annual exports to the US and Europe from turtle packing plants in Nicaragua in excess of 10,000 turtles. Although the processing plants have been closed for over 30 years after Nicaragua became a signatory of CITES in 1977, the local demand for turtle meat in coastal communities has continued. Following themes of cultural ecology and ecological anthropology, we fi rst discuss what is known about the traditional culture of Caribbean Nicaragua, in particular the history of its changing economy (after European contact and settlement on the coast) and subsistence lifestyle of Miskito and Creole societies on the coast. Second, we provide background information on regional ethnic identity and the human ecology of the Caribbean Nicaragua sea turtle fi shery. We then present a quantitative analysis of the relationship between protein preference and various demographic characteristics, and speculate whether protein preferences have been altered in the coastal culture, providing recommendations for future research. Recent studies present disparate views on whether nesting and foraging green turtle populations are increasing or decreasing in the region: in either case the level of harvest makes the topic of protein preference an important and relevant consideration in conservation.

Line Transects by Design: The Influence of Study Design, Spatial Distribution and Density of Objects on Estimates of Abundance

The line transect distance sampling method provides unbiased estimates of abundance when organisms are distributed randomly or line transects are laid out randomly, sample sizes are large and other assumptions of the method are met; such, however, is rarely the case in real life. We conducted a simulation study to investigate how spatial distribution and density of objects, and total length, layout and number of transects influence bias, precision, and accuracy of estimates of abundance obtained by distance sampling along line transects. Overall, density estimated using the distance sampling method was within 4.9% of the true density, but it varied substantially depending upon spatial distribution of objects. Of the three spatial distribution patterns considered, estimates of density were least biased, and most precise and accurate when objects were distributed randomly; they were most biased, and least precise and accurate when objects followed a clumped distribution. The estimated bias (% difference between true density and estimated density) for clumped, random and uniform distribution was 13.1%, -0.4%, and 2.1%, respectively; precision (% coefficient of variation, CV( ˆ D )) was 13.7%, 9.1%, and 9.2%; and accuracy (root mean-squared error, RMSE) was 27.9%, 7.4%, and 11.7% for clumped, random, and uniform distribution, respectively. Increasing total transect length and using several short transects (as opposed to few long transects) generally reduced bias, and increased accuracy and precision of estimates of abundance. A systematic layout of transects worked as well as, or better than, random layout, except when objects were distributed uniformly in space. This study advances the utility of the line transect method by providing information both on how study design affects accuracy and precision of abundance estimates, and how it can be improved when assumptions of the method are not strictly met based on a priori knowledge of the spatial distribution and presumed density of the target organism through appropriate changes in the study design.