Deborah T. Crouse

A Stage‐Based Population Model for Loggerhead Sea Turtles and Implications for Conservation

Management of many species is currently based on an inadequate under- standing of their population dynamics. Lack of age-specific demographic information, particularly for long-lived iteroparous species, has impeded development of useful models. We use a Lefkovitch stage class matrix model, based on a preliminary life table developed by Frazer (1983a), to point to interim management measures and to identify those data most critical to refining our knowledge about the population dynamics of threatened log- gerhead sea turtles (Caretta caretta). Population projections are used to examine the sen- sitivity of Frazers life table to variations in parameter estimates as well as the likely response of the population to various management alternatives. Current management practices appear to be focused on the least responsive life stage, eggs on nesting-beaches. Alternative protection efforts for juvenile loggerheads, such as using turtle excluder devices (TEDs), may be far more effective.

Models to Evaluate Headstarting as a Management Tool for Long‐Lived Turtles

Most turtle species suffer highly mortality in their first year, have a long juvenile period, and can live for decades once they reach adulthood. Conservationists have implemented a number of recovery plans for threatened turtle populations, including experimental headstart programs. Headstarting involves the captive rearing of hatchlings from eggs collected in the wild. The hatchlings are held for several months to help them avoid high mortality in their first year. It is hoped that these turtles survive and grow like wild turtles after release. The purpose of our study was to evaluate headstarting as a management tool for threatened turtle populations. We critically examined the population-level effects of headstarting with a series of deterministic matrix models for yellow mud turtles (Kinosternon flavescens), a non-threatened, well-studied species, endangered Kemps ridley sea turtles (Lepidochelys kempi). We show that management efforts focused exclusively on improving survival in the first year of life are unlikely to be effective for long-lived species such as turtles. Population projections for both turtles predict that head-starting can augment increasing populations when adult survival is returned to or maintained at high levels, provided that headstarted juveniles are as vigorous as wild turtles. However, when subadult and adult survival is reduced, headstarting cannot compensate for losses in later stages. Proportional sensitivity (elasticity) analyses of stage-based matrix models indicated that annual survival rates for subadult and adult turtles are most critical; small decreases in the survival of older turtles can quickly overcome any potential benefits of headstarting. In general, the biological benefits of headstarting programs may be overestimated for turtles, and a careful examination of stage-specific mortality sources, demography, and life history can guide us toward more effective management strategies.

ENDANGERED SPECIES RECOVERY AND THE SCB STUDY: A U.S. FISH AND WILDLIFE SERVICE PERSPECTIVE

As agency biologists with more than 30 years of collective recovery experience, we provide our perspective on the endangered species recovery planning process and the Society for Conservation Biology (SCB) recovery planning study. As part of the continuum from listing through recovery planning and implementation to species recovery and delisting, we believe that clearly written, well-designed recovery plans can play a key role in organizing and focusing the recovery effort for endangered and threatened species. We outline major opportunities, constraints, and limitations of the recovery planning process. Next we discuss some of the major results and recommendations of the SCB recovery plan study and identify 10 action items for further U.S. Fish and Wildlife Service consideration as possible ways to strengthen our recovery program for endangered and threatened species.

Endangered species recovery: A resource allocation problem

Explicit articulation of values and objectives is critical Many nations have laws to identify and protect imperiled species and their ecosystems. In the United States, actions taken under the Endangered Species Act (ESA) have prevented many extinctions, but few listed species have recovered to the point where they can have the ESA protections removed (1, 2). One reason for this [among many (3)] is a shortfall in funding, raising a conundrum for agencies responsible for species recovery: Should resources be allocated toward species facing imminent extinction or species whose long-term survival can most benefit from investment? Some argue that the latter strategy is ethically unsound because it may abandon species with little hope of long-term recovery [for example, (4)], even when science suggests that the former strategy may miss opportunities to prevent species from ever experiencing the risk of imminent extinction (2). We suggest that framing recovery prioritization as a resource allocation problem provides a structure to facilitate constructive debate about such important questions. We discuss here the merits of an explicit resource allocation framework and introduce a prototype decision tool [(5); see supplementary materials for details] that we developed with the U.S. Fish and Wildlife Service (USFWS) to facilitate transparent and efficient recovery allocation decisions.