Blair E. Witherington

Global Conservation Priorities for Marine Turtles

Where conservation resources are limited and conservation targets are diverse, robust yet flexible priority-setting frameworks are vital. Priority-setting is especially important for geographically widespread species with distinct populations subject to multiple threats that operate on different spatial and temporal scales. Marine turtles are widely distributed and exhibit intra-specific variations in population sizes and trends, as well as reproduction and morphology. However, current global extinction risk assessment frameworks do not assess conservation status of spatially and biologically distinct marine turtle Regional Management Units (RMUs), and thus do not capture variations in population trends, impacts of threats, or necessary conservation actions across individual populations. To address this issue, we developed a new assessment framework that allowed us to evaluate, compare and organize marine turtle RMUs according to status and threats criteria. Because conservation priorities can vary widely (i.e. from avoiding imminent extinction to maintaining long-term monitoring efforts) we developed a “conservation priorities portfolio” system using categories of paired risk and threats scores for all RMUs (n = 58). We performed these assessments and rankings globally, by species, by ocean basin, and by recognized geopolitical bodies to identify patterns in risk, threats, and data gaps at different scales. This process resulted in characterization of risk and threats to all marine turtle RMUs, including identification of the worlds 11 most endangered marine turtle RMUs based on highest risk and threats scores. This system also highlighted important gaps in available information that is crucial for accurate conservation assessments. Overall, this priority-setting framework can provide guidance for research and conservation priorities at multiple relevant scales, and should serve as a model for conservation status assessments and priority-setting for widespread, long-lived taxa.

Regional Management Units for Marine Turtles: A Novel Framework for Prioritizing Conservation and Research across Multiple Scales

Background Resolving threats to widely distributed marine megafauna requires definition of the geographic distributions of both the threats as well as the population unit(s) of interest. In turn, because individual threats can operate on varying spatial scales, their impacts can affect different segments of a population of the same species. Therefore, integration of multiple tools and techniques — including site-based monitoring, genetic analyses, mark-recapture studies and telemetry — can facilitate robust definitions of population segments at multiple biological and spatial scales to address different management and research challenges. Methodology/Principal Findings To address these issues for marine turtles, we collated all available studies on marine turtle biogeography, including nesting sites, population abundances and trends, population genetics, and satellite telemetry. We georeferenced this information to generate separate layers for nesting sites, genetic stocks, and core distributions of population segments of all marine turtle species. We then spatially integrated this information from fine- to coarse-spatial scales to develop nested envelope models, or Regional Management Units (RMUs), for marine turtles globally. Conclusions/Significance The RMU framework is a solution to the challenge of how to organize marine turtles into units of protection above the level of nesting populations, but below the level of species, within regional entities that might be on independent evolutionary trajectories. Among many potential applications, RMUs provide a framework for identifying data gaps, assessing high diversity areas for multiple species and genetic stocks, and evaluating conservation status of marine turtles. Furthermore, RMUs allow for identification of geographic barriers to gene flow, and can provide valuable guidance to marine spatial planning initiatives that integrate spatial distributions of protected species and human activities. In addition, the RMU framework — including maps and supporting metadata — will be an iterative, user-driven tool made publicly available in an online application for comments, improvements, download and analysis.

Influences of artificial lighting on the seaward orientation of hatchling loggerhead turtles Caretta caretta

Abstract The seaward orientation behavior of hatchling loggerhead turtles Caretta caretta when exposed to five different artificial light sources (high-pressure) and low-pressure sodium vapor, and yellow, red, and white incandescent lamps) was examined. Each light source affected hatchling sea-finding performance either in direction of orientation or width of dispersion. Hatchlings were attracted to light sources emitting short-wavelength visible light and long-wavelength sources that excluded intermediate wavelengths. A negative response was observed toward sources emitting predominately yellow light. For this reason, low-pressure sodium vapor (LPS) luminaires, which emit only yellow light, are expected to affect loggerhead hatchling sea-finding minimally, if positioned behind the primary dune. LPS luminaires positioned between emerging hatchlings and the ocean, however, will disrupt hatchling orientation.

Hypothermic Stunning and Mortality of Marine Turtles in the Indian River Lagoon System, Florida

indicate that an increase in recruitment occurred between those years. Impacts of these hypothermic stunning events on lagoonal populations, especially green turtles, are potentially devastating. A trapping effect exhibited by Mosquito Lagoon and the northern Indian River may prevent resident turtles from locating refuges thereby contributing to the occurrence of cold-stunning events there. As a possible result of frequent cold-stunning events, fewer green turtles inhabit Mosquito Lagoon than other parts of the Indian River Lagoon System.

Quantifying multiple threats to endangered species: an example from loggerhead sea turtles

The effectiveness of recovery plans for threatened and endangered species has been questioned in academic and political domains. A comprehensive assessment of species recovery plans concluded that quantification and prioritization of threats have received insufficient attention, which contributes to the failure of some plans. On the basis of this assessment, we developed and implemented a detailed analysis of threats in the Recovery Plan for the Northwest Atlantic Population of the Loggerhead Sea Turtle (Caretta caretta), produced by the National Marine Fisheries Service and US Fish and Wildlife Service. The analytical approach that we designed and summarize here provides an objective process for quantifying known threats and prioritizing recovery actions in terms of their relative impact on population growth rate (λ) of the loggerhead sea turtle. Although this process was developed for loggerhead sea turtles, it can be applied to other species.

Better Science Needed for Restoration in the Gulf of Mexico

In the wake of the BP oil spill, U.S. agencies need research plans to collect data that will aid in managing and assessing marine species and ecosystems. The 2010 BP Deepwater Horizon oil spill in the Gulf of Mexico (GoM) has damaged marine ecosystems and jeopardized endangered and commercial species under U.S. jurisdiction (see the figure). Agencies that manage protected species—including the U.S. National Marine Fisheries Service and the U.S. Fish and Wildlife Service—are tasked with recovering these populations. But many populations have not been adequately assessed, so recovery cannot be measured. Achieving mandated recovery goals depends on understanding both population trends and the demographic processes that drive those trends. After the 1989 Exxon Valdez Alaskan oil spill, evaluations of effects on wildlife were ambiguous, in part because limited data on abundance and demography precluded detection of change (1). Sadly, the situation in the GoM is similar more than 20 years later. As concluded in the National Commission report on the BP spill (2) released 11 January, “Scientists simply do not yet know how to predict the ecological consequences and effects on key species that might result from oil exposure…” We argue that scientists know how to make these assessments, but lack critical data to achieve this goal.

Plasma estradiol-17β, progesterone, prostaglandin F, and prostaglandin E2 concentrations during natural oviposition in the loggerhead turtle (Caretta caretta)

Changes in plasma concentrations of steroids and prostaglandins (PGs) during natural nesting and oviposition in the loggerhead turtle were studied. Blood samples were obtained during nine distinct behavioral stages of oviposition. Emerging females had no detectable prostaglandin F (PGF) or prostaglandin E2 (PGE2) whereas plasma estradiol-17 beta averaged 255 pg/ml and mean plasma progesterone was 395 pg/ml. Plasma steroid concentrations did not vary significantly during nesting. In contrast, plasma PGF and PGE2 exhibited significant elevations during nest digging about 15 min after emergence. A further significant increase in plasma PGs was observed 10 min later during early oviposition. Plasma PGE2 peaked during mid oviposition whereas maximal plasma PGF levels occurred during nest covering although mean values were not significantly different than those observed during oviposition. Both PGs showed an abrupt decline (within 10 min) during body pit covering to concentrations similar to those observed during nest construction. Our data suggest that PGs have an active role during oviposition and nesting in the loggerhead turtle and are consistent with hypotheses that PGF2 alpha stimulates uterine contractions promoting egg expulsion while PGE2 may be more important in promoting cervical relaxation.

Leatherback nests increasing significantly in Florida, USA; trends assessed over 30 years using multilevel modeling

Understanding population status for endangered species is critical to developing and evaluating recovery plans mandated by the Endangered Species Act. For sea turtles, changes in abundance are difficult to detect because most life stages occur in the water. Currently, nest counts are the most reliable way of assessing trends. We determined the rate of growth for leatherback turtle (Dermochelys coriacea) nest numbers in Florida (USA) using a multilevel Poisson regression. We modeled nest counts from 68 beaches over 30 years and, using beach-level covariates (including latitude), we allowed for partial pooling of information between neighboring beaches. This modeling approach is ideal for nest count data because it recognizes the hierarchical structure of the data while incorporating variables related to survey effort. Nesting has increased at all 68 beaches in Florida, with trends ranging from 3.1% to 16.3% per year. Overall, across the state, the number of nests has been increasing by 10.2% per year since 1979. Despite being a small population (probably < 1000 individuals), this nesting population may help achieve objectives in the federal recovery plan. This exponential growth rate mirrors trends observed for other Atlantic populations and may be driven partially by improved protection of nesting beaches. However, nesting is increasing even where beach protection has not been enhanced. Climate variability and associated marine food web dynamics, which could enhance productivity and reduce predators, may be driving this trend.

Orientation of hatchling loggerhead turtles at sea off artificially lighted and dark beaches

42 hatchling loggerhead turtles Caretta caretta L. were released at lighted and dark beach sites on the east coast of Florida, USA, and tracked as they swam offshore during daytime and nighttime trials at each site (four groups). Hatchlings from each group swam in straight paths in generally seaward directions. Hatchlings from both NNE-facing (dark beach) and SSE-facing (lighted beach) beaches swam approximately perpendicular to the shore. No differences were found among groups in path straightness or in orientation direction relative to the shoreline surrounding the release point. Hatchlings swimming from the lighted beach at night, however, swam more slowly and had a larger angle of dispersion than did hatchlings from the dark beach at night. Beach lighting was among other site characteristics that may have influenced these behaviors.

Historical versus Contemporary Climate Forcing on the Annual Nesting Variability of Loggerhead Sea Turtles in the Northwest Atlantic Ocean

A recent analysis suggested that historical climate forcing on the oceanic habitat of neonate sea turtles explained two-thirds of interannual variability in contemporary loggerhead (Caretta caretta) sea turtle nest counts in Florida, where nearly 90% of all nesting by this species in the Northwest Atlantic Ocean occurs. Here, we show that associations between annual nest counts and climate conditions decades prior to nest counts and those conditions one year prior to nest counts were not significantly different. Examination of annual nest count and climate data revealed that statistical artifacts influenced the reported 31-year lag association with nest counts. The projected importance of age 31 neophytes to annual nest counts between 2020 and 2043 was modeled using observed nest counts between 1989 and 2012. Assuming consistent survival rates among cohorts for a 5% population growth trajectory and that one third of the mature female population nests annually, the 41% decline in annual nest counts observed during 1998–2007 was not projected for 2029–2038. This finding suggests that annual nest count trends are more influenced by remigrants than neophytes. Projections under the 5% population growth scenario also suggest that the Peninsular Recovery Unit could attain the demographic recovery criteria of 106,100 annual nests by 2027 if nest counts in 2019 are at least comparable to 2012. Because the first year of life represents only 4% of the time elapsed through age 31, cumulative survival at sea across decades explains most cohort variability, and thus, remigrant population size. Pursuant to the U.S. Endangered Species Act, staggered implementation of protection measures for all loggerhead life stages has taken place since the 1970s. We suggest that the 1998–2007 nesting decline represented a lagged perturbation response to historical anthropogenic impacts, and that subsequent nest count increases since 2008 reflect a potential recovery response.