Identifying Anomalous Reports of Putatively Extinct Species and Why It Matters

Abstract:  As species become very rare and approach extinction, purported sightings can stir controversy, especially when scarce management resources are at stake. We used quantitative methods to identify reports that do not fit prior sighting patterns. We also examined the effects of including records that meet different evidentiary standards on quantitative extinction assessments for four charismatic bird species that might be extinct: Eskimo Curlew ( Numenius borealis ), Ivory-billed Woodpecker ( Campephilus principalis ), Nukupu`u ( Hemignathus lucidus ), and O`ahu `Alauahio ( Paroreomyza maculata ). For all four species the probability of there being a valid sighting today, given the past pattern of verified sightings, was estimated to be very low. The estimates of extinction dates and the chance of new sightings, however, differed considerably depending on the criteria used for data inclusion. When a historical sighting record lacked long periods without sightings, the likelihood of new sightings declined quickly with time since the last confirmed sighting. For species with this type of historical record, therefore, new reports should meet an especially high burden of proof to be acceptable. Such quantitative models could be incorporated into the International Union for Conservation of Nature's Red List criteria to set evidentiary standards required for unconfirmed sightings of "possibly extinct" species and to standardize extinction assessments across species.     

State Intervention to Protect Endangered Species: Why History and Bad Luck Matter

Abstract: Illegal exploitation threatens the survival of many species, and anti-poaching legislation ("protection on paper") does not protect species. State enforcement is needed to support and supplement the formal status of endangered species, but state enforcement can be a source of instability leading to the demise of species if ad hoc rules are followed blindly. We demonstrate this with a model of poaching, wildlife, and government wildlife enforcement, but our findings apply more generally. Crucial assumptions of the dynamic model are that both poaching and enforcement effort increase or decrease whenever poaching effort and enforcement are relatively profitable or unprofitable activities, respectively. We found that multiple steady states may characterize the system's equilibrium. Depending on initial populations, the initial extent of state involvement, and random events, animal populations may be severely depleted or unexpectedly built up during transition phases. Our findings highlight the importance of history and luck in protecting endangered species.     

Experimental Tests of Captive Breeding for Endangered Species

Abstract: Several captive breeding regimes were compared for their ability to maintain fitness ( larval viability) and genetic variation in small populations of the housefly ( Musca domestica L.). Populations were either maintained at constant sizes of 40, 200, or 2000 individuals or initiated with two pairs of flies and allowed to grow to 40 individuals ( low-founder-number populations). Low-founder-number populations without migration exhibited low larval viability (22%) after 24 generations, compared to larger populations maintained at either 200 (49%) or 2000 (69%) individuals, and suffered high extinction, with only 44% of the lines surviving 24 generations. Low-founder-number populations subjected to two additional founder ( bottleneck) episodes, reducing them to two pairs of flies, suffered little additional loss in fitness or extinction compared to the single-founder treatments. Migration as low as one individual per generation (2.5% migration) significantly offset both reduced fitness and rate of extinction. Conversely, fitness was not significantly increased for low-founder-number populations when founders were selected from the top performing 20% of pairs under full-sib mating. Populations maintained at 40 individuals were not sustainable, exhibiting low larval viability (35%) and a high extinction rate (40%) over 24 generations, similar to the extinction rates for populations initiated with only four founders. Although none of the populations maintained at 200 individuals went extinct, their fitness was reduced by 20% compared to a large control population maintained at 2000 individuals. Electrophoretic variation was significantly correlated with fitness across treatments, but the correlation of fitness to narrow-sense heritability of two morphometric traits was not significant.     

Designatable Units for Status Assessment of Endangered Species

Abstract:  Species status assessment and the conservation of biological diversity may require defining units below the species level to portray probabilities of extinction accurately and to help set priorities for conservation efforts. What those units should be has been debated in the scientific literature largely in terms of evolutionarily significant units (ESUs), but this discourse has had little impact on government policy with regard to status assessment. As with species concepts, the variously proposed ESU concepts have not been resolvable into a single approach. The need for a practicable procedure to identify infraspecific entities for status assignment is the motivation behind employing designatable units (DUs). In aid of a policy to prevent elements of biodiversity from becoming extinct or extirpated, DUs are determined during the process of resolving a species' conservation status according to broadly applicable guidelines. The procedure asks whether putative DUs are distinguishable based on a reliably established taxonomy or a well-corroborated phylogeny, compelling evidence of genetic distinction, range disjunction, and/or biogeographic distinction as long as extinction probabilities also differ. The language of the DU approach avoids wording that implies value judgments concerning evolutionary importance or significance. Because species conservation status assessment is not science but, rather, the use of science to further policy, DUs contribute to a precautionary approach to listing whereby status may be assessed even though knowledge of systematic relationships below the species level may be lacking or unresolved. The pragmatic approach of using DUs has been adopted by the Committee on the Status of Endangered Wildlife in Canada for status assessment of species under the Canadian Species at Risk Act.     

Six Biological Reasons Why the Endangered Species Act Doesn't Work—And What to Do About It

Abstract: Law plays an important role in shaping land management decisions. The success of efforts to conserve biodiversity thus depends to a large degree on how well scientific knowledge is translated into public policy. Unfortunately, the Endangered Species Act, the United States's strongest legal tool for conserving bidodiversity, contains serious biological flaws. The statute itself, as well us agency regulations and policies that implement the law include provisions that fail to account accurately for important biological concepts such us ecosystem conservation, patch dynamics, and the probabilistic nature of stochastic threats to a species' persistence. Moreover, the procedures of federal agencies charged with implementing the Endangered Species Act in some cases make it difficult for interested outside reviewers to evaluate the agencies' scientific findings and methodology. However, the Endangered Species Act also gives interested individuals and groups several opportunities to provide input into the process of managing threatened and endangered species. Conservation biologists should practice focused advocacy by taking advantage of such opportunities to steer law in a more biologically sound direction.     

Demography and Population Viability of an Endangered Plant Species before and after Protection from Trampling

Land managers often suggest fencing to protect rare plant species from being trampled in heavily used recreation areas, but there are few documented examples of the efficacy of this strategy. In a 7-year demographic study we examined the reproduction, survival, and long-term viability of the endangered sentry milk-vetch (Astragalus cremnophylax var. cremnophylax) before and after protection from trampling. Demographic monitoring and population viability analyses indicated that the population has fluctuated during the 7 years. Before protection the population declined: 26% of individuals died, mortality surpassed natality, and age of first reproduction was significantly older than post-protection. Fifty-eight percent of the population was severely damaged. Population viability analyses of pre-protection years predicted that the population would go extinct within 100 years. Since protection, the population stabilized, grew, and declined again. Seedlings reached reproductive maturity more quickly. Recruitment increased and peaked in 1993 coincident with abundant precipitation, but again declined in 1994. The total numbers of undamaged plants surpassed the numbers of damaged plants. Models of the post-protection population predict stability. Multiple-linear regression analysis indicated that winter and spring precipitation were significantly correlated with lambda. Both "good" and "bad" climatic conditions occurred during the pre- and post-protection periods. Because of small population size and depauperate genetic diversity, climate will continue to influence population growth. Nevertheless, models indicate that where trampling and bad climatic conditions were coupled, extinction was accelerated. Recovery of sentry milk-vetch will depend on continued protection, augmentation, and environmental factors, although risk of extinction remains very high.     

Protected Areas and Prospects for Endangered Species Conservation in Canada

Abstract:  Reserve networks figure prominently in conservation strategies that aim to reduce extinction rates. We tested the effectiveness of the current reserve network at protecting species at risk in Canada, where relatively extensive wilderness areas remain. We compared numbers of terrestrial species at risk included in existing reserves to randomly generated networks with the same total area and number of reserves. Existing reserve networks rarely performed better than randomly selected areas and several included fewer endangered species than expected by chance, particularly in the most biologically imperiled regions. The extent of protected area and density of species at risk were unrelated at either broad (countrywide) or finer spatial scales (50 × 50 km grids), although there was a tendency for the most threatened regions of the country to have few or no protected areas (1.5% of areas with >30 endangered species were in reserves). Although reserves will play a useful role in conserving endangered species that occur within them, reducing extinction rates in a region with much of the world's remaining wilderness will require integrating conservation strategies with agricultural and urban land-use plans outside formally protected areas.     

Control of Abundant Native Vertebrates for Conservation of Endangered Species

Abundant native vertebrates, which we define as those that have increased in abundance due to human-induced changes in communities or ecosystems, have contributed to the decline of rare vertebrates through predation, competition, habitat change, disease transmission, and hybridization. Recent literature dealing with the negative effects of abundant native vertebrates on rare native vertebrates argues for population control by killing or translocating animals. We identify several potential problems with these methods, including the high cost of population control, community changes such as mesopredator release that favor other harmful vertebrate species, and increases in diseases harmful to the rare species. Also, public opposition to and lack of species specificity in population control techniques often make population control difficult. We propose alternatives to population reduction/or management of abundant native vertebrates, including techniques that prevent abundant vertebrates from causing harm, and community and ecosystem rehabilitation and restoration. The latter provide the best solutions to problems caused by abundant native vertebrates because community and ecosystem degradation are the primary factors responsible for some species becoming rare and others becoming abundant. These solutions are long term, biologically sound, and involve little direct human intervention into ecosystem processes. But population control may be necessary as a short-term solution when abundant vertebrates pose an immediate threat to the survival of a rare species. We conclude that those involved in the conservation of rare species should consider population control of abundant native vertebrates only as a last resort.     

Limitations of Captive Breeding in Endangered Species Recovery

The use of captive breeding in species recovery has grown enormously in recent years, but without a concurrent growth in appreciation of its limitations. Problems with (1) establishing self-sufficient captive populations, (2) poor success in reintroductions, (3) high costs, (4) domestication, (5) preemption of other recovery techniques, (6) disease outbreaks, and (7) maintaining administrative continuity have all been significant. The technique has often been invoked prematurely and should not normally be employed before a careful field evaluation of costs and benefits of all conservation alternatives has been accomplished and a determination made that captive breeding is essential for species survival. Merely demonstrating that a species' population is declining or has fallen below what may be a minimum viable size does not constitute enough analysis to justify captive breeding as a recovery measure. Captive breeding should be viewed as a last resort in species recovery and not a prophylactic or long-term solution because of the inexorable genetic and phenotypic changes that occur in captive environments. Captive breeding can play a crucial role in recovery of some species for which effective alternatives are unavailable in the short term. However, it should not displace habitat and ecosystem protection nor should it be invoked in the absence of comprehensive efforts to maintain or restore populations in wild habitats. Zoological institutions with captive breeding programs should operate under carefully defined conditions of disease prevention and genetic/behavioral management. More important, these institutions should help preserve biodiversity through their capacities for public education, professional training, research, and support of in situ conservation efforts.