Larisa Avens

Relationship between barnacle epibiotic load and hematologic parameters in loggerhead sea turtles (Caretta caretta), a comparison between migratory and residential animals in Pamlico Sound, North Carolina.

Abstract Health status of a total of 57 loggerhead sea turtles (Caretta caretta; 42 migratory and 15 residential turtles) was analyzed using body condition and hematologic parameters. A subset of 18 juvenile migratory loggerhead sea turtles in the fall of 1997 and 15 residential turtles in the summer of 2000 were analyzed for barnacle epibiota. The migratory group had significantly higher red blood cell counts and percent heterophils and significantly lower percent lymphocyte and absolute eosinophil counts, as well as significantly lower plasma concentrations of calcium, sodium, chloride, potassium, glucose, alkaline phosphatase, and anion gap. Many of these variations may be because of physiology of migration. A positive association between turtle weight and hematocrit was detected and may be because of larger turtles diving for longer periods of time. There were no significant differences of epibiota load, health of the turtles, or condition index between turtles captured during the two events.

Navigation and seasonal migratory orientation in juvenile sea turtles

SUMMARY Juvenile loggerhead and green turtles that inhabit inshore waters of North Carolina, USA undertake long seasonal migrations, after which they often return to specific feeding areas. In addition, juvenile turtles are capable of homing to specific sites after being displaced. As a first step towards investigating the navigational mechanisms that underlie these movements, juvenile turtles were captured in coastal waters of North Carolina and displaced 30–167 km along circuitous routes while deprived of visual cues. At the testing location, turtles were tethered in a circular arena and permitted to swim while their orientation was monitored. Between May and September, when juvenile loggerhead and green turtles inhabit feeding areas along the North Carolina coast, turtles oriented in directions that corresponded closely with the most direct route back to their capture locations. During October and November, however, both loggerhead and green turtles oriented southward, a direction consistent with the migratory paths of turtles beginning their autumn migration. The results demonstrate for the first time that both homing and migratory orientation can be elicited in juvenile turtles under laboratory conditions in which orientation cues can be readily manipulated. In addition, the results provide evidence that juvenile loggerheads can assess their position relative to a goal using local cues available at the test site and are therefore capable of map-based navigation.

Responses of hatchling sea turtles to rotational displacements

After emerging from underground nests, sea turtle hatchlings migrate through the surf zone and out to the open ocean. During this migration, both waves and water currents can disrupt hatchling orientation by unpredictably rotating the turtles away from their migratory headings. In addition, waves cause turtles to roll and pitch, temporarily impeding forward swimming by forcing the hatchlings into steeply inclined positions. To maintain seaward orientation and remain upright in the water column, hatchlings must continuously compensate for such displacements. As a first step toward determining how this is achieved, we studied the responses of loggerhead (Caretta caretta L.) sea turtle hatchlings to rotational displacements involving yaw, roll, and pitch. Hatchlings responded to rotations in the horizontal plane (yaw) by extending the rear flipper on the side opposite the direction of rotation. Thus, the flipper presumably acts as a rudder to help turn the turtle back toward its original heading. Turtles responded to rotations in the roll plane with stereotypic movements of the front flippers that act to right the hatchlings with respect to gravity. Finally, hatchlings responded to rotations in the pitch plane with movements of the hind flippers that appear likely to curtail or counteract the pitching motion. Thus, the results of these experiments imply that young sea turtles emerge from their nests possessing a suite of stereotypic behavioral responses that function to counteract rotational displacements, enable the animals to maintain equilibrium, and facilitate efficient movement toward the open sea.

Patterns of loggerhead turtle ontogenetic shifts revealed through isotopic analysis of annual skeletal growth increments

Ontogenetic changes in resource use often delimit transitions between life stages. Ecological and individual factors can cause variation in the timing and consistency of these transitions, ultimately affecting community and population dynamics through changes in growth and survival. Therefore, it is important to document and understand behavioral and life history polymorphisms, and the processes that drive intraspecific variation in them. To evaluate juvenile loggerhead sea turtle (Caretta caretta) life history variation and to detect shifts in habitat and diet that occur during an oceanic-to-neritic ontogenetic shift, we sequentially analyzed the stable isotope composition of humerus bone growth increments from turtles that stranded dead on Southeastern U.S. beaches between 1997 and 2013 (n = 84). In one-half of the sampled turtles, growth increment-specific nitrogen stable isotope (δ15N) data showed significant increases in δ15N values over each turtles life. These data were used to provide a new line ...

Summer Abundance Estimates of Caretta caretta (Loggerhead Turtles) in Core Sound, NC

Abstract We estimated summer abundance of juvenile Loggerhead Turtles at our study site in Core Sound, NC with a Horvitz-Thompson type estimator, which uses count data and recapture probability to estimate abundance. Abundance ranged from 192 (95% CI = 88–1047) to 633 (95% CI = 219–1047) turtles over the six years of this study. These results provide preliminary estimates of juvenile Loggerhead Turtle abundance during the summer in Core Sound.

Methods for sampling sequential annual bone growth layers for stable isotope analysis

Methods in Ecology and Evolution 2016 doi: 10.1111/2041-210X.12522 Methods for sampling sequential annual bone growth layers for stable isotope analysis Calandra N. Turner Tomaszewicz 1,2 *, Jeffrey A. Seminoff 2 , Larisa Avens 3 and Carolyn M. Kurle 1 Division of Biological Sciences, Ecology, Behavior and Evolution Section, University of California, San Diego, La Jolla, CA 92093-0116, USA; 2 Southwest Fisheries Science Center, NOAA, National Marine Fisheries Service, La Jolla, CA 92037, USA; and 3 Southeast Fisheries Science Center, NOAA, National Marine Fisheries Service, Beaufort, NC 28516, USA Summary 1. Stable carbon (d 13 C) and nitrogen (d 15 N) isotope analysis (SIA) has proven useful in addressing fundamental questions in ecology such as reconstructing trophic interactions, habitat connections and climate regime shifts. The temporal scales over which SIA can be used to address ecological problems vary depending on the protein turnover times of the analysed tissue. Hard, inert tissues, such as teeth, bones and mollusc shells, grow in regular intervals (i.e. daily or annually), and sequential sampling of these growth layers provides a time series of isotopic patterns. As a result, SIA on these tissues is useful for elucidating behaviour and ecology of animals over time, especially those with cryptic life-history stages, such as marine turtles that retain growth layers in their humerus bones. To date, there exists no standard protocol for the sequential sampling of cortical bone samples taken from fresh, modern samples for SIA. 2. We tested two different methods, micromilling untreated bone cross sections and biopsy coring bone cross sec- tions processed for skeletochronology, for sequentially sampling individual growth layers from marine turtle humerus bones. 3. We present a standard protocol for sequential bone growth layer sampling for SIA, facilitating direct compar- ison of future studies. We recommend using the micromilling sampling technique on untreated bone cross sec- tions, as it facilitated higher precision sampling of growth layers that were not affected by chemical processing, and minimized sample handling, thereby reducing chances for contamination. 4. This is the first study to present a standardized method to sequentially sample annual bone growth layers for stable isotope analysis and facilitates direct comparison among future studies. Key-words: bone, collagen, marine turtles, sequential sampling, skeletochronology, stable isotope analysis Introduction Stable carbon (d 13 C) and nitrogen (d 15 N) isotope analysis (SIA) of organic matter is a powerful tool used in ecological studies to elucidate diet, trophic level, habitat use and migra- tion of a wide variety of taxa in both marine (e.g.Vander Zan- den & Rasmussen 2001; Michener & Lajtha 2007; Graham et al. 2010; Newsome, Clementz & Koch 2010) and terrestrial (e.g. Koch, Fogel & Tuross 1994; Hobson, Barnett-Johnson & Cerling 2010) systems. Examination of both d 13 C and d 15 N values from animal tissues allows for reconstruction of animal movement patterns due to spatial variation in these values that reflect differential carbon and nitrogen processing at the base of terrestrial and marine food webs (DeNiro & Epstein 1978; Rau et al. 1983; Clementz & Koch 2001; McMahon, Hamady & Thorrold 2013). Different tissues incorporate and retain stable isotopes from the diet at varying rates, allowing researchers to investigate for- aging ecology over multiple time-scales by sampling-specific *Correspondence author. E-mail: cturnert@ucsd.edu tissues (Hobson 1999; Dalerum & Angerbj€ orn 2005; Reich, Bjorndal & Martinez del Rio 2008; Kurle 2009). Many hard tissues, such as bone, teeth, otoliths, corals and bivalve shells, do not have regular cellular turnover; instead, subsequent lay- ers formed during growth are retained. These inert layers pre- serve their original chemical composition, thereby reflecting the stable isotope values of the environment and the prey con- sumed during the formation of a particular growth layer (e.g. Elorriaga-Verplancken et al. 2013). This creates a time series of data reflecting an animal’s diet and location when layers are formed at regular time intervals (e.g. days for otolith rings, or years for bone, tooth, coral and tree rings). Sequential SIA of growth layers has been conducted on tis- sues such as otolith and teeth (e.g. Schwarcz et al. 1998; Hob- son 1999; Newsome et al. 2006; Elorriaga-Verplancken et al. 2013) with promising results for reconstructing habitat use pat- terns for migratory megafauna. For some marine turtle spe- cies, humerus bone tissue is deposited in annual layers (e.g. Snover et al. 2011) and, recently, sequential SIA of marine tur- tle bone growth layers identified by skeletochronology has been successful, generating a time series reflecting the diet and

Variability in age and size at maturation, reproductive longevity, and long-term growth dynamics for Kemp's ridley sea turtles in the Gulf of Mexico

Effective management of protected sea turtle populations requires knowledge not only of mean values for demographic and life-history parameters, but also temporal and spatial trends, variability, and underlying causes. For endangered Kemp’s ridley sea turtles (Lepidochelys kempii), the need for baseline information of this type has been emphasized during attempts to understand causes underlying the recent truncation in the recovery trajectory for nesting females. To provide insight into variability in age and size at sexual maturation (ASM and SSM) and long-term growth patterns likely to influence population trends, we conducted skeletochronological analysis of humerus bones from 333 Kemp’s ridleys stranded throughout the Gulf of Mexico (GOM) from 1993 to 2010. Ranges of possible ASMs (6.8 to 21.8 yr) and SSMs (53.3 to 68.3 cm straightline carapace length (SCL)) estimated using the “rapprochement” skeletal growth mark associated with maturation were broad, supporting incorporation of a maturation schedule in Kemp’s ridley population models. Mean ASMs estimated from rapprochement and by fitting logistic, generalized additive mixed, and von Bertalanffy growth models to age and growth data ranged from 11 to 13 yr; confidence intervals for the logistic model predicted maturation of 95% of the population between 11.9 and 14.8 yr. Early juvenile somatic growth rates in the GOM were greater than those previously reported for the Atlantic, indicating potential for differences in maturation trajectories between regions. Finally, long-term, significant decreases in somatic growth response were found for both juveniles and adults, which could influence recruitment to the reproductive population and observed nesting population trends.

Chronic debilitation in stranded loggerhead sea turtles (Caretta caretta) in the southeastern United States: Morphometrics and clinicopathological findings

Chronically debilitated loggerhead sea turtles (Caretta caretta) (DT) are characterized by emaciation, lethargy, and heavy barnacle coverage. Although histopathological findings associated with this condition have been reported, only limited data is available on health variables with clinical application. The objectives of this study were to 1) to compare morphometrics, clinicopathological variables, and immune functions of DTs to a group of apparently healthy loggerhead turtles to better understand the pathophysiology of the condition and 2) to assess health parameters in live debilitated turtles as they recovered during rehabilitation in order to identify potential prognostic indicators. We examined and sampled 43 DTs stranded from North Carolina to Florida for 47 health variables using standardized protocols to further characterize the condition. DTs were grouped into categories of severity of the condition, and those that survived were sampled at four time points through rehabilitation. All groups and time points were compared among DTs and to clinically healthy loggerhead turtles. Compared to healthy turtles, DTs had significantly lower body condition index, packed cell volume (PCV), total white blood cell (WBC) count, lymphocytes, glucose (Glc), total protein, all protein fractions as determined by electrophoresis, calcium (Ca), phosphorus (P), Ca:P ratio, potassium (K), lymphocyte proliferation, and greater heterophil toxicity and left-shifting, uric acid (UA), aspartate aminotransferase, creatine kinase, lysozyme, and respiratory burst. From admission to recovery, hematology and plasma chemistry data improved as expected. The most informative prognostic indicators, as determined by correlations with a novel severity indicator (based on survival times), were plastron concavity, P, albumin, total solids, UA, lymphocyte proliferation, WBC, K, Glc, Ca:P, and PCV. The results of this study document the wide range and extent of morphometric and metabolic derangements in chronically debilitated turtles. Monitoring morphometrics and clinicopathological variables of these animals is essential for diagnosis, treatment, and prognosis during rehabilitation.