Dune vegetation fertilization by nesting sea turtles

Sea turtle nesting presents a potential pathway to subsidize nutrient-poor dune ecosystems, which provide the nesting habitat for sea turtles. To assess whether this positive feedback between dune plants and turtle nests exists, we measured N concentration and delta N-15 values in dune soils, leaves from a common dune plant ( sea oats [Uniola paniculata]), and addled eggs of loggerhead (Caretta caretta) and green turtles ( Chelonia mydas) across a nesting gradient ( 200 - 1050 nests/km) along a 40.5-km stretch of beach in east central Florida, USA. The delta N-15 levels were higher in loggerhead than green turtle eggs, denoting the higher trophic level of loggerhead turtles. Soil N concentration and delta N-15 values were both positively correlated to turtle nest density. Sea oat leaf tissue delta N-15 was also positively correlated to nest density, indicating an increased use of augmented marine-based nutrient sources. Foliar N concentration was correlated with delta N-15, suggesting that increased nutrient availability from this biogenic vector may enhance the vigor of dune vegetation, promoting dune stabilization and preserving sea turtle nesting habitat

Inferring Foraging Areas of Nesting Loggerhead Turtles Using Satellite Telemetry and Stable Isotopes

In recent years, the use of intrinsic markers such as stable isotopes to link breeding and foraging grounds of migratory species has increased. Nevertheless, several assumptions still must be tested to interpret isotopic patterns found in the marine realm. We used a combination of satellite telemetry and stable isotope analysis to (i) identify key foraging grounds used by female loggerheads nesting in Florida and (ii) examine the relationship between stable isotope ratios and post-nesting migration destinations. We collected tissue samples for stable isotope analysis from 14 females equipped with satellite tags and an additional 57 untracked nesting females. Telemetry identified three post-nesting migratory pathways and associated non-breeding foraging grounds: (1) a seasonal continental shelf-constrained migratory pattern along the northeast U. S. coastline, (2) a non-breeding residency in southern foraging areas and (3) a residency in the waters adjacent to the breeding area. Isotopic variability in both delta C-13 and delta N-15 among individuals allowed identification of three distinct foraging aggregations. We used discriminant function analysis to examine how well delta C-13 and delta N-15 predict female post-nesting migration destination. The discriminant analysis classified correctly the foraging ground used for all but one individual and was used to predict putative feeding areas of untracked turtles. We provide the first documentation that the continental shelf of the Mid-and South Atlantic Bights are prime foraging areas for a large number (61%) of adult female loggerheads from the largest loggerhead nesting population in the western hemisphere and the second largest in the world. Our findings offer insights for future management efforts and suggest that this technique can be used to infer foraging strategies and residence areas in lieu of more expensive satellite telemetry, enabling sample sizes that are more representative at the population level

Modeling and mapping isotopic patterns in the Northwest Atlantic derived from loggerhead sea turtles

Stable isotope analysis can be used to infer geospatial linkages of highly migratory species. Identifying foraging grounds of marine organisms from their isotopic signatures is becoming de rigueur as it has been with terrestrial organisms. Sea turtles are being increasingly studied using a combination of satellite telemetry and stable isotope analysis; these studies along with those from other charismatic, highly vagile, and widely distributed species (e.g., tuna, billfish, sharks, dolphins, whales) have the potential to yield large datasets to develop methodologies to decipher migratory pathways in the marine realm. We collected tissue samples (epidermis and red blood cells) for carbon (delta C-13) and nitrogen (delta N-15) stable isotope analysis from 214 individual loggerheads (Caretta caretta) in the Northwest Atlantic Ocean (NWA). We used discriminant function analysis (DFA) to examine how well delta C-13 and delta N-15 classify loggerhead foraging areas. The DFA model was derived from isotopic signatures of 58 loggerheads equipped with satellite tags to identify foraging locations. We assessed model accuracy with the remaining 156 untracked loggerheads that were captured at their foraging locations. The DFA model correctly identified the foraging ground of 93.0% of individuals with a probability greater than 66.7%. The results of the external validation (1) confirm that assignment models based on tracked loggerheads in the NWA are robust and (2) provide the first independent evidence supporting the use of these models for migratory marine organisms. Additionally, we used these data to generate loggerhead-specific delta C-13 and delta N-15 isoscapes, the first for a predator in the Atlantic Ocean. We found a latitudinal trend of delta C-13 values with higher values in the southern region (20-25 degrees N) and a more complex pattern with delta N-15, with intermediate latitudes (30-35 degrees N) near large coastal estuaries having higher delta N-15-enrichment. These results indicate that this method with further refinement may provide a viable, more spatially-explicit option for identifying loggerhead foraging grounds

Activity, Population-Size And Structure Of Immature Chelonia-Mydas And Caretta-Caretta In Mosquito Lagoon, Florida

Mosquito Lagoon, located on the east-central coast of Florida, was found to be a developmental habitat for two species of sea turtles. Populations of the green (Chelonia mydas) and loggerhead (Caretta caretta) turtles found in the lagoon were studied from July, 1976 to March, 1979. All green turtles were immature (N = 108; range 30-59.1 kg); 40% of the sampled individuals weighed less than 20 kg. Almost all loggerheads were immature (N = 104; range 12.8-97.7 kg); only 6% of the sampled number were heavier than 80 kg. Both species of turtles were present in the lagoon throughout the year. Chelonia was more susceptible to net capture during the warmer months. Nocturnal activity was not apparent in either species. The role of developmental habitats in the life history of both species is discussed

Digging behavior of four species of deer mice (Peromyscus). American Museum novitates ; no. 2429

16 p. : ill. ; 24 cm.Includes bibliographical references (p. 15-16)."Certain aspects of digging behavior in four species of deer mice, Peromyscus (P. floridanus, P. gossypinus, P. leucopus, and P. polionotus), were studied to determine the relationships between the level of digging activity and ecological factors and the possible adaptive significance of such correlations. Two populations of each of three of the species (floridanus, gossypinus, and polionotus) were included to provide some indication of the magnitude of intraspecific variation in digging activity, and both field and first generation laboratory-raised subjects of the same species were studied in an attempt to distinguish between the relative influences of genetic and environmental factors on this behavior. Mice were placed individually into an open-field box containing either sand or peat and observed for a five-minute period. In addition to descriptive notes on digging behavior, number of bouts, total time spent digging, and latency (time elapsed between introduction to the apparatus and beginning of first digging bout) were recorded. Peromyscus floridanus dug relatively slowly, using the forefeet for excavating and moving material beneath the body and also to propel the substrate to the rear. In contrast to the other species, the hind feet were rarely used to kick accumulated material backward. Peromyscus gossypinus moved the forefeet more rapidly in excavating material than did floridanus and generally used the hind limbs to throw the substrate behind the body. Details of digging in leucopus were not clearly observed; but it appears to resemble gossypinus in its style of digging. Peromyscus polionotus appeared to be the most efficient digger of the four species. It moved its forefeet more rapidly than the other forms, and the hind limbs were more closely integrated into the total action pattern. Quantitatively, floridanus dug less than the other species, gossypinus and leucopus were slightly more active, whereas polionotus far exceeded all other species in mean number of bouts and total time digging and had distinctly shorter latencies. The well-developed digging behavior of polionotus is correlated with burrowing habits. All species exhibited a tendency to dig more actively on sand rather than on peat, but only in leucopus and polionotus was the discrepancy pronounced. The higher level of digging of polionotus on sand may reflect selection for substrate recognition as a result of the importance of the proper type of soil for burrow construction in this species. There seems to be no obvious adaptive basis for the sand preference of leucopus. Only in polionotus were there appreciable differences between populations in digging behavior, with leucocephalus tending to do more digging than did subgriseus. This difference may reflect more intense selection for digging in the leucocephalus population as a result of more difficult burrow construction and maintenance, constant covering of food items by blowing sand, and greater use of shallow holes to avoid predation. In general, laboratory-raised stocks fell into the same relative position as field groups in the aspects of digging behavior studied, indicating a genetic basis of the differences observed. However, in all stocks except P. p. leucocephalus there was a tendency for reduced digging in laboratory-reared subjects. The differences between field and laboratory-raised groups appear to be of environmental origin, either reflecting the absence of experience on natural substrates or an effect of the homogeneous laboratory environment on other aspects of behavior, such as activity, temperament, etc., which in turn influence digging performance. The fact that laboratory-reared leucocephalus actually dug more than did field subjects may indicate either a stronger genetic basis for digging in this stock or a lesser effect of laboratory conditions, perhaps because of the relative homogeneity of the natural environment of this population compared with that of the other stocks. Differences in the present results and those of previous studies of digging behavior in Peromyscus dealing with some of the same species appear to be attributable to the types of testing apparatus and procedures utilized"--P. 14-15