Photo: Peter C. H. Pritchard Conservation Strategies—An Overview:
Implications for Management

Peter C. H. Pritchard

Chelonia Institute, 401 South Central Avenue, Oviedo, FL 32765, USA
Florida Audubon Society, 1331 Palmetto, Suite 110, Winter Park, FL 32789, USA

        Polite friends and relatives, making small talk, often ask me, “How are the turtles doing?”  The focus of my professional life involves trying to find the answer to this question, but I assume that they do not really want several hours of commentary, and I generally give a brief and noncommittal reply.  But the time has come that the question must be answered to whatever extent that is possible, and it may best be rephrased, “In a world where human impact reaches into almost every corner, how much punishment can turtle populations and turtle species take?”

        The optimist would make certain observations, as follows:
        • Apart from some giant tortoises on small islands (Pritchard, 1996), and perhaps one or two mud turtle subspecies in island-like refugia (namely isolated water holes in arid terrain, Iverson, 1981), we have not yet lost any taxa to extinction at the hand of man.
        • Turtles logically must have some ultimate mechanism for responding to factors that cause population reduction or increase in such a way as to reduce the effect of those factors; otherwise, every natural population trend, upwards or downwards, would have continued either to infinity or extinction by now.  Yet this has obviously not happened for any extant population.
        • Many turtles are ecological generalists and can do well even in disturbed or unnatural habitat.  Thus, red-eared sliders (Trachemys scripta elegans) can live almost anywhere; gopher tortoises (Gopherus polyphemus) do best in habitat that has been prevented from forming a closed canopy, by regular burning, hurricane action, etc.; and even the rare bog turtle (Clemmys muhlenbergii) may do well in habitat that has been influenced by such activities as cattle grazing.
        • Tortoises (Testudinidae) are presumably amongst the slower breeding of chelonian species, yet even they have the capacity to reach spectacular concentrations within a few decades.  We note the huge population of giant tortoises (Aldabrachelys elephantina) on Aldabra Atoll (over 130,000 animals), or the thousands of bowsprit tortoises (Chersina angulata) on Dassen Island, off eastern South Africa.  The former population has expanded from an almost extinct natural population in 1890–1900 (Swingland, 1989), while Dassen Island, a speck of land only 222 hectares, has a population of tens of thousands of tortoises, reportedly derived from a founder stock of unknown but presumably small size introduced between 1896 and 1929 (Branch, 1991).  This increase has occurred despite seemingly low reproductive potential (a single egg per clutch) and relatively severe predation on the juveniles by Kelp Gulls.  Both situations attest to the power of geometric increase, once it gets under way in simple, closed ecosystems.
        • The demonstrated “take” (capture or slaughter) that some turtle populations seem to have tolerated is sometimes impressive.  Loggerhead sea turtles are gradually increasing in Florida despite tens of thousands of drowning mortalities annually, in recent years, by shrimp trawlers (National Research Council, 1990).  The olive ridley colony in Oaxaca, Mexico was subjected to an annual take of many thousands of animals per year for over 20 years, yet in the year following the final closure of the legal take, arribadas of very large—and annually increasing—size were observed (Márquez et al., 1996).  And, around the Mediterranean, where casual pickup of tortoises of the genus Testudo has occurred at least since Greek and Roman times, and continues to this day (whether for food, personal pets, commercial export, or manufacture of musical instruments), and where in recent decades a great deal of environmental destruction and highway mortality has occurred as well, tortoise populations continue to survive in most areas.  Their documented retreat (e.g., in France, Devaux, 1988) is probably a result of both natural climatic shift and total conversion of habitat; the tortoises often survive well in areas of low-intensity viniculture, such as has been conducted near La Pardiguière (Guyot, 1995).
        A tropical parallel would be the situation of the yellow-footed tortoise in forests of Amazonia and the Guianas.  Throughout the range of this species, it is safe to say that virtually any time human eyes fall upon a specimen, it is collected for food (or, much more rarely, for the wildlife trade).  Moreover, this has probably occurred for thousands of years.  Yet the species remains abundant.

        To these observations, the pessimist would make reply as follows:
        • The extinctions that have occurred at the hand of early man have almost certainly been severe.  Thus, the extinction of once-widespread giant tortoises in continental and continental-island ecosystems, including North America, the Caribbean, and Madagascar, almost certainly resulted from human predation (possibly in tandem with climate change).  Moreover, we are today in the midst of widespread, steady decline of most species, and we can anticipate numerous extinctions in the decades to come.
        • Careful studies by Ron Brooks and his co-workers in Guelph (Galbraith et al., this volume) have demonstrated that an Ontario population of the common snapping turtle—the epitome of a robust species to most people—showed no density-dependent response or population recovery following a stochastic population-depletion event, and the conclusion was made that there was no possibility of sustained exploitation of mature turtles from populations at such latitudes.
        • Not all turtles are ecological generalists.  For example, map turtles (Graptemys) demonstrate specialization for pristine riverine conditions, and in circumstances where rivers have been heavily impacted by siltation, as has occurred in northeastern Arkansas, the map turtles may disappear and be replaced by the more tolerant Trachemys.  Similarly, bog turtles, while tolerant of certain kinds of habitats with some degree of disturbance, have very precise “bog habitat” requirements, and their overall range thus shows trenchant discontinuities.  The South African geometric tortoise, Psammobates geometricus, has demands for such a specialized habitat type (“renosterveld”) that it cannot tolerate significant land alteration or even progressive, natural closure of the tree canopy (an event held at bay by fire, which ironically also kills many individuals of this non-burrowing species).  The conversion of about 97% of its habitat to grape and wheat cultivation has reduced the range of the species by the same percentage (Baard, this volume).
        • In isolated situations turtles may be able to increase geometrically to impressive population densities, but in most continental situations, informal observation by those whose interests or inclination causes them to notice turtles and tortoises indicates that, even in the absence of directed or obvious threats, populations progressively diminish from one year to the next.  Witness, for example, the anecdotal but highly persuasive evidence for decreases in the “common” box turtle in many areas in the eastern United States in recent decades (Dodd and Franz, 1993), although on islands, even those with dense exotic vegetation, like Egmont Key Florida, impressively dense populations may build up (Dodd et al., 1994).  In this case the population increase is fostered by a fortuitous combination: absence of mammalian predators, insignificant or absent human take, and a dense population of cockroaches that constitutes a crucial prey item.
        • There are many reported situations that contrast sharply with the apparently large sustainable take of certain turtle populations.  A number of these relate to species that are not evenly distributed over large tracts of land, but rather exist in microhabitats within a wide—or not-so-wide—overall range.  Examples include the aforementioned bog turtle; Blanding’s turtle (Emydoidea blandingii) in the northeastern United States (Congdon et al., 1993); the African pancake tortoise (Malacochersus tornieri) (Wood and MacKay, this volume); and probably other tortoise species, such as Manouria impressa, Homopus boulengeri, and H. signatus, which have very specialized habitat requirements.  In cases like these, removal of just a few individuals from an individual deme may cause local extirpation and, because dispersal across alien habitat is chancy at best (and impossible at worst), recolonization may not occur within any practical time frame.  But even in such cases, an isolated population may recover from an episode of collecting, if the harvest is not sustained—witness the reported recovery of a pancake tortoise population in Kenya within slightly over a decade after heavy exploitation (Wood and MacKay, this volume).

— o000o —
        The present volume is a goldmine of information on the population status, dynamics, and prospects of the tortoises and turtles of the world.  When combined with the papers in the proceedings of the slightly more recent turtle conservation conference in Gonfaron, France (SOPTOM, 1995), it should be possible for us to come to some general conclusions to answer that naive but crucial question, “How are the turtles doing?”
        The conclusions below are derived from my basically subjective evaluation of many scientific contributions from many parts of the world.  I consider it entirely possible that a different commentator could arrive at significantly different conclusions, or at least present different emphases and propose different priorities.
        • Species or populations that are naturally rare, or demes or populations of species existing near the latitudinal extremes of their natural range, are presumably rare for a reason.  They are living under some kind of adverse circumstances that limit their success and their population increase.  Reproduction or recruitment may fail entirely except in favorable years, and populations “hang on” mainly because of the longevity of adults.  This being the case, the superimposition of sustained anthropogenic take or other stress upon these natural, limiting factors and hardships is likely to lead to progressive depletion and ultimately extirpation or extinction.
        • Nonetheless, the generalization above should not be incautiously extended to populations living in more optimal habitat.  In the various cases mentioned above in which abundant or robust turtle populations have survived heavy and protracted collection, it appears that some sort of enhanced recruitment or survival of juvenile year-classes, or even reduction of maturation time, may have occurred.  A real-world example is offered by the two localities in Pacific Costa Rica where the olive ridley nests in great concentrations or arribadas.  One of these sites, Playa Nancite, is constrained between rocky headlands about a kilometer apart and is totally protected from human interference by its national park status.  Turtle populations progressively built up to such a level that the entire beach was overcrowded, the incubation medium became polluted by the remains of destroyed eggs, and hatching success dropped to about 1% (Cornelius, 1986).  Now the adult population is starting to show a sharp decline.  Meanwhile, on Ostional Beach to the south, a modest level of legal exploitation of the eggs has probably enhanced hatching success, which is significantly greater than that reported for Nancite, and the nesting population remains robust.
        • In a stable, unexploited turtle population living in equilibrium within its ecosystem, it is indeed true that sexually mature individuals, especially females, are extraordinarily important.  In most cases such animals should be protected at all costs.  Nevertheless, some managers have extrapolated this rule to the indefensible corollary that, because adults are important, eggs are unimportant.  While it is clear that a given breeding adult is more crucial than a given egg, the “real-world” question is nevertheless different from this, and harder to answer; it may be summarized as, “Is it better to take 100 kg of adult turtles or 100 kg of eggs?”
        Oblivious of such subtleties, some managers have tolerated excessive levels of egg exploitation for human consumption, without having any idea how many eggs must be protected to maintain the overall population.  This careless approach to eggs caused the collapse of the population of Kemp’s ridley in the Gulf of Mexico and North Atlantic, and of the green turtle and leatherback populations in Malaysia (Talang Islands and Terengganu).  Any wildlife manager will insist that animal populations can only be sustained if they are allowed to reproduce safely, yet some turtle biologists seem to have forgotten this fundamental principle.  Nests and eggs must receive substantial protection; otherwise, although the population collapse may be delayed for many years, when it comes it will be irreversible.
        • It is important not to be sidetracked by an excessively theoretical approach.  One must have some hypothesis or theory to justify what one is doing, but the variables are so many that there is no substitute for careful monitoring to determine the actual outcome of a conservation program (as opposed to the anticipated outcome).  Population biology and ecology have not yet reached the point where one can predict the outcome of any given manipulation of a reptile population in quantitative terms.  I take respectful issue, for example, with the Desert Tortoise Recovery Team identifying its goal as giving the Mojave population a 50% chance of survival 500 years from now (Berry, this volume)—partly because the goal is too modest (“survival” means that at least a few individuals survive; thus, the chance of “recovery,” a minor subset of the “survival” outcome, is actually far less than 50%)—and partly because one should, in the words of Margaret Thatcher, “never prophesy anything, especially about the future.”  It is now about 500 years since Columbus landed, and the absurdity of any prediction made in 1492 accurately reflecting the state of the nation or the world in the 1990s is obvious.  Moreover, things are moving faster than ever these days; we don’t even know what will happen a year from now, and the limitations on prediction offered by chaos theory and forces of contingency are now understood.  About the only area of modern life where we look for prediction and expect any degree of success is in weather forecasting, and even there we restrict our expectations of accuracy to the next few days only.
        • USDI and NMFS turtle recovery plans have often been utilized as excuses for decade-long delays in taking any conservation action.  The mandate of the typical team—to ignore political considerations, to identify every single potential or actual stress upon a species or population, and to make sure that every agency represented on the team is allowed to protect its “turf”—has not been a recipe for quick action or success.  Obvious, feasible, essential tasks are diluted by exhaustive inventories of theoretical, hopeless, or unnecessary recommended actions; the preparation of the average plan for listed vertebrate species takes 9.4 years (Tear et al., 1995).  Sometimes only a single severe but easily identifiable stress may be holding a species back, and if this is corrected, the natural resilience of the species alone may allow it to tolerate other stresses.
        In many cases, it would be far better for the whole job of preparing the recovery plan to be contracted out to a competent individual who knows the species, knows conservation biology, and knows his politics.  Then one would have a result in three months, it would have a theme—even a vision—rather than a mere consensus, and it would be politically realistic without being politically compromised.  A lot of conservation dollars, and a lot of time, would be saved.
        • The general public, not to mention the herpetoculturist, is keenly aware of—and much dismayed by—the vulnerability of the hatchling stage of turtle life.  Awkwardly straddling the philosophical fence between K- and r-selected reproductive strategies, turtle hatchlings are big enough to be cute and small enough to die in droves.  Most hatchlings, even of species that are not particularly prolific, simply do not make it.  It is a fortunate one that finds a safe retreat that is protected from climatic and humidity extremes and predators, which also offers adequate nutrition, for enough time, to allow the animal to grow and consolidate its bony shell until it can afford to be seen in public.  Yet few professionals (apart from Mrosovsky, 1983) view this phase, during which the vast majority of individual turtles die of non-intrinsic causes (i.e., “bad luck” rather than genetic deficiency), as a conservation opportunity.  In the case of Kemp’s ridley, a bi-national, interagency, expensive, multi-year conservation effort finally yielded positive results for which the key factor may well have been headstarting (Pritchard, 1997).  But the Recovery Plan (USFWS/NMFS, 1992) was conspicuously silent on the subject of headstarting.  On the narrowly legalistic grounds that headstarting is an experiment, and experiments have no place in a recovery plan, no place was found for headstarting among the recommended actions.  (It could be mentioned that virtually everything we do to enhance turtle populations is experimental, and the actual impact on the population of almost any manipulation remains speculative.)
        Nat Frazer (this volume), who is one of the more brilliant theorists behind the science of turtle conservation biology, implies that manipulation of such juvenile stages to enhance survival or replace excessive take of post-hatchlings, juveniles, or adults is “half-way technology,” which attacks symptoms rather than root causes.  He is obviously right, but I prefer to emphasize that effective conservation plans, like good politics, represent “the art of the possible,” and the correction of the fundamental wrongs of the world, while worth attempting (we are nothing if not optimists), may not be successful or may not yield results in time.  In cases where root causes cannot be easily reversed and species or populations are disappearing, we have to do what Gerald Kuchling (this volume) has done in Western Australia with Pseudemydura, or Roger Wood (this volume) has done in New Jersey with diamondback terrapins (Malaclemys), and take matters in hand to ensure some recruitment where little or none would otherwise occur.
        • Theoreticians and pessimists should note that there is now, at last, good evidence that headstarting does work, and headstarted turtles can contribute to breeding populations.  It has happened with Kemp’s ridley (Pritchard, 1997) and with the Hood Island Galápagos tortoise (Cayot and Morillo, this volume).  Indeed, it may have saved both of those taxa.
        Today, the heavy hand of man is extirpating whole populations, even whole species of rare or localized turtles in eastern and southeastern Asia, and is seriously depleting even widespread ones.  A billion people in China, formerly constrained from regular consumption of luxury foods like turtle by lack of cash, are wielding new-found economic power.  Ross Perot might describe the “giant sucking sound” of millions of turtles being wrenched from their habitats in Laos, Cambodia, Bangladesh, Vietnam, Malaysia, and Indonesia to meet the insatiable demand and high prices offered by Chinese markets.  Even the newly described Geoemyda yuwonoi, whose natural range encompasses just a small area in northern Sulawesi, Indonesia (McCord et al., 1995), and represented in hardly any museums, is starting to appear in numbers in Chinese markets.  And professional collectors report that several of the new taxa of Chinese box turtles described in recent years can no longer be found.  They may or may not be biologically extinct, but they are apparently commercially extinct.  Even the long-known and relatively widespread Cuora trifasciata, found in both China and Vietnam and formerly a common pet trade species, now fetches $1,000 per kilo on eastern markets.
        I see no prospect of reversing these trends in any reasonable time frame by outside action.  We are faced with the appalling choice of either doing nothing, or attempting to save at least a genetic remnant of the species in question by captive breeding.  The latter option is not my first choice, and I am not capitulating to the lobbying pressure of herpetoculturists who are keen to acquire specimens without restrictions and who have advocated captive breeding as the method of choice all along.  But there may be no other way.
        This will require a new partnership between conservationists, zoological parks, government conservation agencies, and private breeders and hobbyists.  Some of the latter may need a little redirection (away from preoccupation with designer snakes, albinos, and similar anomalies), but it is in this community that the husbandry expertise resides, not to mention the financial resources and interest.  The majority of turtle species are actually relatively easy to maintain alive in captivity, and potentially to breed also, although there is a hard core of notoriously “difficult” forms—Malayemys, Morenia, Manouria impressa, Notochelys platynota, Psammobates, and Homopus—that rarely survive long in captivity, let alone breed.  The softshells (Trionychidae) also, although kept for generations in often-filthy “tanks” in eastern temples, seem very susceptible to rapidly fatal skin eruptions in captivity.
        Perhaps a widespread captive breeding program for depleted and endangered chelonian species would result in the happy dilemma faced by the average crocodilian headstarting, ranching, or captive-breeding program—after one crocodilian generation or so, the question of what on earth to do with all these fast-growing, hungry crocodiles (or caimans, or alligators) quickly becomes acute.  In the case of turtles, creative minds could devise a formula for the percentage of offspring to be retained as breeding stock, how many to release into areas of local depletion or extirpation, how many to distribute to other institutions and individuals, and—most controversial of all—how many to sell on lucrative private markets in order to make the entire operation economically self-supporting, and perhaps even generate a surplus to allow for land acquisition or habitat management.

Literature Cited:

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