bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Taxonomy and the Conservation of the Red Wolf and Other Endangered Carnivores
Authors: Brownlow C. Alexander
Published: March 2003

Recent publications have reaffirmed that the red wolf (Canis rufus) is a hybrid of the coyote and the gray wolf. Besides the implications these results will likely have for future conservation efforts and allotment of resources through the Endangered Species Act for recovery of the red wolf, it is likely that broader consequences will be felt throughout the conservation community as species come under the scrutiny of a more powerful means of taxonomic identification. As molecular technology is refined in its ability to resolve taxonomic histories and uncertainties, it is likely that hybridization event(s) will be recognized in more species. This may be of particular importance for large carnivores, whose small population sizes make them susceptible to hybridization episodes with closely related, sympatric species. Because of negative perceptions, powerful antipredator advocates, conservation and resource constraints, and an enigmatic hybrid policy within the Endangered Species Act, how red‐wolf taxonomy is decided by the U.S. Fish and Wildlife Service may affect the future of large carnivores in general.
Epidemic Disease and the Catastrophic Decline of Australian Rain Forest Frogs
Authors: Laurance William F. , McDonald Keith R. , Speare Richard
Published: March 2003

In the montane rain forests of eastern Australia at least 14 species of endemic, stream‐dwelling frogs have disappeared or declined sharply (by more than 90%) during the past 15 years. We review available information on these declines and present eight lines of evidence that collectively suggest that a rapidly spreading, epidemic disease is the most likely responsible agent. The extreme virulence of the putative frog patbogen suggests it is likely exotic to Australian rain forests. We propose that exotic pathogens may be responsible for some recent declines of amphibian populations on other continents and that the intercontinental spread of such pathogens is greatly facilitated by human activities such as the thriving international trade in aquarium fish. Our hypothesis may help explain why some amphibian populations in seemingly pristine environments have mysteriously declined.
Designing the Ark: Setting Priorities for Captive Breeding
Authors: Balmford Andrew , Mace Georgina M. , Leader‐Williams N.
Published: March 2003

Zoos can help conserve only a small minority of the species threatened with extinction. Clear and rational criteria for identifying which threatened taxa zoos should focus on are therefore essential. Current priorities for ex situ conservation stress the importance of large vertebrates. We show that this hampers the efficient use of resources because such species are less likely to breed well in captivity than smaller‐bodied taxa and, despite longer generation lengths, are more costly to maintain in long‐term breeding programs. Moreover, although reintroduction to the wild frees zoo space for other species and is the ultimate aim of captive breeding, zoos show no tendency to target species for which continued habitat availability makes reintroduction a realistic prospect. We suggest that zoos adopt selection criteria that reflect the economic and biological realities of captive breeding and reintroduction if they are to maximize their contribution to species conservation, and we present data on the preferences of zoo visitors indicating that doing so need not adversely affect zoo attendance.
Whooping Crane Recovery: A Case Study in Public and Private Cooperation in the Conservation of Endangered Species
Authors: Cannon John R.
Published: March 2003

I describe three theoretical approaches to endangered species conservation: public‐sector models, private‐sector models, and mixed models. Criteria to consider in evaluating these models are scientific, economic, legal, ethical, and administrative. The history of conservation efforts on behalf of the endangered Whooping Crane (Grus americana) is used as an example of a mixed‐model approach (one that involves both public‐ and private‐sector organizations and individuals) to the conservation of endangered species. Evaluation of Whooping Crane conservation efforts, using the specified criteria, suggests that this mixed model gets relatively high marks in all areas. My recommendations for endangered species conservation activities include (1) ensuring that all potential sources of scientific expertise and “caring” are included, (2) developing a robust national funding mechanism for endangered species conservation efforts, and (3) creating streamlined administrative structures and operating procedures tailored to the unique needs of each endangered species conservation team. Broader implications of the Whooping Crane story for conservation biology as a profession and for conservation biologists as individuals include (1) being inclusive rather than exclusive in conservation planning and implementation, (2) recognizing the power of individual initiative and commitment, (3) collecting basic data over an extended period of time, and (4) emphasizing the importance of communication, cooperation, and coordination.
Land Use, Lag Times and the Detection of Demographic Change: The Case of the Acorn Woodpecker
Authors: Ligon J. David , Stacey Peter B.
Published: March 2003

Changes in land‐use patterns that alter habitat may have a delayed negative effect on animal species occupying that habitat, and thus such effects may not be recognized for years. In Water Canyon, located in the Magdalena Mountains of southcentral New Mexico, we studied a relatively stable population of the cooperatively breeding Acorn Woodpecker (Melanerpes formicivorus) from 1975 to 1984. These woodpeckers rely on self‐constructed storage sites, or “granary trees,” to hold the acorns used during the winter and spring. Most granaries were in dead trunks and limbs of the narrow‐leafed cottonwood trees (Populus angustifolia. Storage sites form the primary basis for differential quality among territories. Groups of woodpeckers with large storage facilities (high‐quality territories) have greater annual reproductive success and survival than do pairs or groups with poorly developed storage sites. In the summers of 1994 and 1995 we censused the original study site, which had held 21 territories. Most territories that had contained birds a decade earlier were unoccupied. This drastic decline was correlated with the loss of nearly all large storage facilities because of the collapse of the granary trees. Most neighboring territories with lesser storage facilities also were vacant. The lack of production of new, high‐quality granaries for the period 1975–1995 probably is due inpart to the age structure of the cottonwood trees, which is distinctly bimodal: nearly all trees are either very young or old. There are now fewer old, partly dead trees that could provide granary sites. The scarcity of middle‐aged trees reflects a period of intensive cattle grazing in Water Canyon, during which time production of young cottonwoods was suppressed.
Prairie Landscape Change and Flooding in the Mississippi River Valley
Authors: Miller Mark W. , Nudds Thomas D.
Published: March 2003

Extensive landscape alteration of prairie in the U.S. from agricultural expansion has reduced waterfowl populations and increased precipitation runoff into regional river basins. Satellite imagery shows that prairie landscapes have been less altered in Canada than in the U.S. Long‐term, broad‐scale precipitation data indicate that in both countries precipitation has varied widely but has not increased over time. Nevertheless, flow rates of unregulated U.S. rivers have increased, but there have been no detectable changes in flow rates of Canadian rivers. Neither of two competing hypotheses advanced to explain increasing flood magnitudes—climate change and channel confinement—can account for these results. Thus, the increased magnitudes of floods in the Mississippi River Valley over the last several decades may be at least partially related to extensive changes in agricultural land use resulting in reduction of natural upland vegetation and wetland drainage in the upper reaches of this watershed.
Conservation Biology and Carnivore Conservation in the Rocky Mountains
Authors: Noss Reed F. , Quigley Howard B. , Hornocker Maurice G. , Merrill Troy , Paquet Paul C.
Published: March 2003

Large carnivores need large areas of relatively wild habitat, which makes their conservation challenging. These species play important ecological roles and in some cases may qualify as keystone species. Although the ability of carnivores to control prey numbers varies according to many factors and often is effective only in the short term, the indirect effects of carnivores on community structure and diversity can be great. Perhaps just as important is the role of carnivores as umbrella species (i.e., species whose habitat area requirements encompass the habitats of many other species). Conservation areas large enough to support populations of large carnivores are likely to include many other species and natural communities, especially in regions such as the Rocky Mountains of Canada and the United States that have relatively low endemism. For example, a plan for recovery of grizzly bears (Ursus arctos) proposed by Shaffer (1992) covers, in part, 34% of the state of Idaho (compared to 8% covered by a U.S. Fish and Wildlife Service proposal) and would capture 10% or more of the statewide ranges of 71% of the mammal species, 67% of the birds, 61% of the amphibians but only 27% of the reptiles native to Idaho. Two‐thirds (67%) of the vegetation types in Idaho would have 10% or more of their statewide area included in the Shaffer plan. The U.S. Fish and Wildlife Service recovery zones provide a much poorer umbrella. The umbrella functions of large carnivores are expected to be poorer in regions with high endemism. The application of metapopulation concepts to large carnivore conservation has led to proposals for regional reserve networks composed of wilderness core areas, multiple‐use buffer zones, and some form of connectivity. The exceptional vagility of most large carnivores makes such networks feasible in a region with low human population density, such as the Rocky Mountains, but mortality risks still need to be addressed. Roads are a major threat to carnivore recovery because of barrier effects, vehicle collisions, and increased accessibility of wild areas to poachers. Development, especially for tourism, is also becoming a threat in many parts ofthe region.
Use of Riparian Buffer Strips as Movement Corridors by Forest Birds
Authors: Machtans Craig S. , Villard Marc‐André , Hannon Susan J.
Published: March 2003

We conducted a 3‐year field experiment to measure the frequency of bird movements through riparian buffer strips before and after harvesting of adjacent forest. Our study was conducted in the boreal mixed wood forest of Alberta and was designed to determine empirically whether songbirds use riparian buffer strips of forest connecting forest reserves as corridors and if they move along these buffer strips more frequently than they cross adjacent clearcuts. We used mist nets to obtain an index of the frequency of bird movement in the forest, and we observed bird movements across adjacent clearcuts for comparison. We predicted that the frequency of movement would be greater (1) in buffer strips after harvesting of adjacent forest than before harvesting, (2) in buffer strips than across clearcuts and, (3) in buffer strips than at control sites (lakeshore forest with no adjacent clearcuts). After adjusting for year‐to‐year variation in abundance, we found that capture rates increased significantly from pre‐ to post‐harvest, but only for juveniles. Capture rates of adults decreased immediately after harvesting, probably because of the removal of an adjacent source of birds that previously moved through the lakeside forest. Movement rates of forest species in clearcuts were significantly lower than capture rates in the forest. The number of adults captured was positively correlated with the number of territories in the buffer strips, indicating that most birds captured were probably residents. The number of local territories was a poor predictor of juvenile captures, supporting the notion that juveniles were likely dispersing individuals. Our results indicate that buffer strips enhanced movements of juveniles (i.e., acted as corridors) and maintained movement rates of adults. Furthermore, there appeared to be a threshold distance between reserves below which birds may be less reluctant to fly across openings, making corridor use less important.
Analyses of Globally Threatened Anatidae in Relation to Threats, Distribution, Migration Patterns, and Habitat Use
Authors: Green Andy J.
Published: March 2003

New World Conservation Union criteria for globally threatened status are applied to the Anatidae (ducks, geese, and swans) at the subspecific level. Various characteristics of the 48 threatened taxa are considered. These taxa are compared to the 180 taxa that are nonthreatened to explain what aspects of a taxon’s distribution, migration pattern, and habitat use make it likely to be globally threatened. Habitat loss, hunting, and exotic introductions are the major causes of globally threatened status, affecting 73%, 48%, and 33% of threatened Anatidae respectively. Although the habitat use patterns of threatened and nonthreatened Anatidae are similar, inland lentic wetland and forest inhabitants are most threatened by habitat loss, whereas marine ecosystem, grassland, tundra, arable land, and scrub dwellers are least threatened. Insular taxa are more likely to be threatened or extinct than taxa occurring on continental land masses. Nonmigratory taxa are more likely to be threatened or extinct than migratory taxa, but there is no significant difference when insular taxa are excluded from the analysis. Taxa with their breeding distribution centered above a latitude of 20° north are less threatened than those found farther south. Taxa with their breeding distribution centered at or above 55° north are even less threatened. Russia holds 14 threatened Anatidae taxa, more than any other country. There is an exceptional concentration of 7 threatened, migratory taxa confined to the east‐Asian flyway. Despite the fact that the Ramsar Convention was established with the conservation of the Anatidae in mind, only 31% of globally threatened taxa have ever been recorded on the world’s 685 Ramsar sites. For the 21 highly threatened taxa this proportion drops to 10%. Compared with globally threatened birds in general, the threatened Anatidae have a different geographical distribution but share habitat loss as the most important threat. Hunting and introductions are more important threats to the Anatidae, and trade and small population ranges are less important. All these findings have important implications for waterbird and wetland conservation programs.
Conservation Implications of Genetic Differentiation in Southern African Populations of Black Rhinoceros (Diceros bicornis)
Authors: Swart M. K. J. , Ferguson J. W. H.
Published: March 2003

We analyzed 30 protein‐coding loci of four southern African black rhinoceros populations in order to calculate fixation indices and genetic distances for the different populations. We concluded that one of these populations is of the subspecies Diceros bicornis bicornis and the other three of Diceros bicornis minor. No evidence of inbreeding within populations was found. F‐ statistics revealed significant differentiation between populations. Small genetic distances found among the four populations reveal that they are conspecific, and no evidence was found to support the claim that the populations belong to discrete subspecies. Rather, an east‐west cline in genetic characteristics appears to exist with G6pd and HB‐2 alleles peculiar to western populations and Es‐2 and GP‐3 alleles peculiar to eastern populations.
History and Importance of Land Use and Protection in the North Quabbin Region of Massachusetts (USA)
Authors: Golodetz Alisa D. , Foster David R.
Published: March 2003

Evaluating the consequences and future of land protection requires broad temporal and spatial perspectives of ecological and cultural factors. We assessed the development of a system of protected areas comprising 37% of central Massachusetts in terms of changing rates and means of land protection. We compared protected areas to the surrounding matrix in terms of physical, biological, and historical features and used these results to raise issues concerning future planning. The rate, purpose, and means of land protection in the North Quabbin Region (168,312 ha) have been dynamic as a result of changes in cultural values and transformation of the landscape from predominantly agriculture to forest. Protected lands are managed by 25 federal and state agencies, private groups, and municipal departments and commissions and are physically and biologically typical of the regional landscape which results from (1) participation of diverse organizations with varied agendas; (2) predominance of large government acquisitions driven by landscape‐scale criteria; and (3) absence of coordination among groups. The large area, relative homogeneity and largely undeveloped status of the North Quabbin Region suggest conservation goals distinct from those in the fragmented and extensively developed neighboring areas of the Connecticut River Valley and Cape Cod and Islands Region. Large tracts of forests, wetlands, and lakes in the North Quabbin Region provide (1) habitat for species requiring extensive, intact areas; (2) the opportunity to maintain broad‐scale ecological processes; (3) connections to regional conservation areas; and (4) recreation. To realize the area’s potential, a comprehensive plan must be based on a broad‐scale perspective and historical understanding of the landscape.
Mitigation of Habitat “Take”: Application to Habitat Conservation Planning
Authors: Bingham Bruce B. , Noon Barry R.
Published: March 2003

One of the most important provisions of the U.S. Endangered Species Act precludes the “taking” of listed species on both public and private land. In past Endangered Species Act litigation, take has been broadly interpreted to include the destruction or modification of habitats as well as the direct killing of animals. This requirement created an extensive burden on private landowners to provide habitats for listed species. This burden was substantially lessened when the ESA was modified in 1982 to allow incidental takings conditioned on preparation of a satisfactory “habitat conservation plan.” Because the majority of listed species are imperiled due to habitat modification, most habitat conservation plans must demonstrate defensible methods to mitigate against incidental habitat loss. A review of HCPs for the Northern Spotted Owl ( Strix occidentalis), and other species, indicates that mitigation solutions are often arbitrary, lacking an empirical foundation in the species’ life history requirements. Based on data from the Spotted Owl, we illustrate a biologically based method for estimating the areal requirements necessary to mitigate against the take of essential habitats. Toward this goal we adopt the concept of “core area,” that portion of an animal’s home range that receives disproportionate use. We estimated core areas by means of the adaptive kernel density function and tested against a null distribution of animal use that assumes a bivariate, uniform distribution of locations within the home range. The method we illustrate, which is defensible, repeatable, and empirical, is a clear improvement over the ad hoc methods used in many habitat conservation plans. Further, the methods we propose should be applicable to a large number of terrestrial species for which home range is a meaningful concept.
Conservation Genetics of North American Freshwater Mussels Amblema and Megalonaias
Authors: Mulvey Margaret , Lydeard Charles , Pyer Debra L. , Hicks Kimberly M. , Brim‐Box Jayne , Williams James D. , Butler Robert S.
Published: March 2003

Freshwater bivalves are among the most endangered groups of organisms in North America. Efforts to protect the declining mussel fauna are confounded by ambiguities associated with recognition of distinct evolutionary entities or species. This, in part, is due to the paucity of reliable morphological characters for differentiating taxa. We have employed allozymes and DNA sequence data to search for diagnosably distinct evolutionary entities within two problematic genera of unionid mussels, Amblema and Megalonaias. Within the genus Amblema three species are recognized based on our DNA sequence data for the mitochondrial 16S rRNA and allozyme data (Amblema neislerii, A. plicata, and A. elliotti). Only one taxonomically distinct entity is recognized within the genus Megalonaias—M. nervosa. Megalonaias boykiniana of the Apalachicolan Region is not diagnosable and does not warrant specific taxonomic status. Interestingly, Megalonaias from west of the Mississippi River, including the Mississippi, exhibited an allozyme and mtDNA haplotype frequency shift suggestive of an east‐west dichotomy. The results of this study eliminate one subspecies of Amblema and increase the range of A. plicata. This should not affect the conservation status of “currently stable” assigned to A. plicata by Williams et al. (1993). The conservation status of A. elliotti needs to be reexamined because its distribution appears to be limited to the Coosa River System in Alabama and Georgia.
Deforestation Predicts the Number of Threatened Birds in Insular Southeast Asia
Authors: Brooks Thomas M. , Pimm Stuart L. , Collar Nigel J.
Published: March 2003

The world’s tropical forests are being cleared rapidly, and ecologists claim this is causing a massive loss of species. This claim has its critics. Can we predict extinctions from the extent of deforestation? We mapped the percentage of deforestation on the islands of the Philippines and Indonesia and counted the number of bird species found only on these islands. We then used the species‐area relationship to calculate the number of species predicted to become globally extinct following deforestation on these islands. Next, we counted the numbers of insular southeast Asian endemic bird species considered threatened—i.e., those having “a high probability of extinction in the wild in the medium‐term future”—in the latest summary Red Data Book. The numbers of extinctions predicted from deforestation and the numbers of species actually threatened are strikingly similar. This suggests we can estimate the size of the extinction crisis in once‐forested regions from the extent of deforestation. The numbers of extinctions will be large. Without rapid and effective conservation, many of the species endemic to insular southeast Asia will soon be lost.
Hunting and the Likelihood of Extinction of Amazonian Mammals
Authors: Bodmer Richard E. , Eisenberg John F. , Redford Kent H.
Published: March 2003

Species inhabiting tropical forests are thought to be on the verge of mass extinction. Much work has focused on extinction rates caused by deforestation; however, many of the recorded extinctions that have occurred since 1600 were a result of overhunting. We collected data on the relative abundance of large‐bodied mammals in the northeastern Peruvian Amazon in areas with persistent hunting pressure and in areas with infrequent hunting pressure. We quantified the effects of hunting by calculating the change in abundance of species between the infrequently and persistently hunted sites. We report that in Amazonian mammals weighing more than 1 kg the degree of population declines caused by hunting is correlated with the species’ intrinsic rate of natural increase (rmax  ), longevity, and generation time. Our results show that species with long‐lived individuals, low rates of increase, and long generation times are more vulnerable to extinction than species with short‐lived individuals, high rates of increase, and shorter generations.
Risk Analysis of Hunting of Seal Populations in the Baltic
Authors: Kokko Hanna , Lindström Jan , Ranta Esa
Published: March 2003

Vulnerabilities of grey seal ( Halichoerus grypus) and ringed seal ( Phoca hispida) populations in the Baltic Sea were evaluated for potential opening of the populations for hunting. We used ecological risk analysis to assess the effects of environmental and demographic stochasticity and uncertain and partly missing population data on the modeled outcomes. The impact of different harvesting strategies on the long‐term sustainability of seal populations was analyzed with four different models with increasing complexity and population detail. It appears the simpler the population model used, the more overconfident results it gave with regard to the hunting policy to be adopted. Therefore, it proves risky in population management decisions to rely on simplistic calculations based on growth rate and estimated population size alone. This is even more so if the population estimates have a wide error margin. Due to an unknown, but presumably positive number of seal kills in the Baltic at present, the sustainable harvest is likely to be close to zero for both seal species. Our risk analysis strongly suggests refraining from Baltic seal hunting now, with their current population sizes, and in the future if the development of population numbers cannot be assessed accurately enough.
Gap Crossing Decisions by Forest Songbirds during the Post‐Fledging Period
Authors: Desrochers André , Hannon Susan J.
Published: March 2003

Gaps in forest cover, created by agriculture, forestry, and other anthropogenic activities, are assumed to impede the movements of many forest songbirds. Little is known, however, about the reluctance of different species of birds to cross habitat gaps. We studied this by inducing birds in the post‐fledging period to cross gaps of varying widths and to choose between routes through woodland or across open areas by attracting them to a recording of mobbing calls by Chickadees (  Parus atricapillus). In 278 experiments conducted in boreal forest and agricultural landscapes near Québec city, 157 birds or flocks of birds of five species were attracted. Overall, birds were twice as likely to travel through 50 m of woodland than through 50 m in the open to reach the recording. When given a choice of traveling through woodland or across a gap, the majority of respondents preferred woodland routes, even when they were three times longer than shortcuts in the open. However, species differed greatly in their response to gaps. Our results show that woodland links significantly facilitate movements of birds across fragmented landscapes.
Genetic Structure of Fragmented Populations of the Endangered DaisyRutidosis leptorrhynchoides
Authors: Young A. G. , Brown A. H. D. , Zich F. A.
Published: March 2003

Abstract:The endangered grassland daisyRutidosis leptorrhynchoideshas been subject to severe habitat destruction and fragmentation over the past century. Using allozyme markers, we examined the genetic diversity and structure of 16 fragmented populations. The species had high genetic variation compared to other plant species, and both polymorphism and allelic richness showed strong positive relationships with log reproductive population size, reflecting a loss of rare alleles (frequency ofq< 0.1) in smaller populations. Fixation coefficients were positively related to size, due either to a lack of rare homozygotes in small populations or to Wahlund effects (owing to spatial genetic structure) in large ones. Neither gene diversity nor heterozygosity was related to population size, and other population parameters such as density, spatial contagion, and isolation had no apparent effect on genetic variation. Genetic divergence among populations was low , despite a large north‐to‐south break in the species’ current distribution. To preserve maximum genetic variation, conservation strategies should aim to maintain the five populations larger than 5000 reproductive plants, all of which occur in the north of the range, as well as the largest southern population of 626 plants at Truganina. Only one of these is currently under formal protection. High heterozygosity in smaller populations suggests that they are unlikely to be suffering from inbreeding depression and so are also valuable for conservation. Erosion of allelic richness at self‐incompatibility loci, however, may limit the reproductive capacity of populations numbering less than 20 flowering plants.
A Large‐Scale Model of Wolf Distribution in Italy for Conservation Planning
Authors: Corsi Fabio , Duprè Eugenio , Boitani Luigi
Published: March 2003

The 400–500 wolves currently living in the Apennine range of peninsular Italy are slowly recolonizing the Alps and are expected to move northward. A nationwide management plan for the Italian wolf population is being prepared, and a zoning system with connecting corridors has been suggested. We developed a large‐scale probabilistic model of wolf distribution as a contribution to the planning process. Thirteen environmental variables related to wolf needs and human presence were analyzed in 12 well‐studied wolf territories and in 100 areas where the species has been absent for the past 25 years. These two areas were used as a training set in a discriminant analysis to evaluate potential wolf presence throughout the entire country. We used the Mahalanobis distance statistic as an index of environmental quality, calculated as the distance from the average environmental conditions of the wolf territories. Based on the Mahalanobis distance statistics, we constructed an actual and potential spatial distribution of the wolf for all of peninsular Italy. The jackknife procedure was used to assess the stability of the distance model and showed good confidence in our model (coefficient of variation ≤ 13%). Distance from the wolf territories’ centroid as an index of environmental quality for the wolf was tested using 287 locations where wolves have been found dead in the past 25 years as a consequence of human action (poison, shotgun, car accidents). A useful contribution to conservation planning resulted from comparing the frequency distribution of the Mahalanobis distance of the dead wolf locations with the percentage of study area within each distance class. This showed how the number of wolf casualties would greatly decrease with protection of only a minor part of the study area and indicated the usefulness of our approach for evaluation of other conservation options, such as core areas and corridor identification.
Interactions among Frugivores and Fleshy Fruit Trees in a Philippine Submontane Rainforest
Authors: Hamann Andreas , Curio Eberhard
Published: March 2003

Abstract: We assessed the potential effect of frugivore extinctions on forest regeneration in the North Negros Forest Reserve, a forest fragment that is one of the last remaining wet tropical rainforest ecosystems in the biogeographic region of the central Philippine Islands. We evaluated foraging observations of 19 species of birds, fruit bats, and other mammals in three successional habitats and identified tree species that are potentially at risk because their seeds are dispersed by frugivores that are seriously endangered. The relative abundance of zoochorous trees in this forest community was exceptionally high (80%), suggesting that the process of forest regeneration will change drastically if endangered frugivores are hunted to extinction. We grouped 45 tree species as early‐, mid‐, or late‐successional species based on their population structure and we demonstrated that early‐successional tree species were visited by a wide spectrum of frugivores, whereas mid‐ and late‐successional species were visited mostly by hornbills (Bucerotidae) and fruit pigeons (Columbidae). Late‐successional tree species were most specialized with respect to dispersers and could therefore be susceptible to extinction. We recommend tree species that could be useful for assisted natural regeneration projects in the reserve because they are visited by a variety of frugivores. Of those, we recommend early‐successional trees for open‐field plantations and mid‐successional tree species for enrichment plantings.
A Framework for Conceptualizing Human Effects on Landscapes and Its Relevance to Management and Research Models
Authors: McIntyre S. , Hobbs Richard
Published: March 2003

Abstract: The concept of habitat fragmentation is limited in its ability to describe the range of possible landscape configurations created by a variety of disturbances. This limitation is especially problematic in landscapes where human use of the habitat matrix occurs at multiple levels and where habitat modification may be a more important consideration than a simple binary classification of habitat versus nonhabitat. We propose a synthesizing scheme that places intact, variegated, fragmented, and relictual landscape states on a continuum, depending on the degree of habitat destruction. At a second level, the scheme considers the patterns of habitat modification that are imposed on remaining habitats. Management for conservation involves halting and sometimes reversing the trends of habitat destruction and modification. Conservation strategies will differ according to the state of alteration of the landscape, but all strategies include some consideration of the degree of modification of the matrix in determining habitat viability. It is convenient for biologists to assess landscape alteration state in terms of the persistence of large structural elements such as trees. Because animal species use habitats differently, however, they also experience the landscape differently. A landscape considered structurally fragmented by humans may be functionally variegated to other species. Therefore, it is necessary to consider the extent to which the entire landscape, including the matrix, is accessible and utilized by organisms with different spatial scales of resource use.
Effects of a Population Bottleneck on Whooping Crane Mitochondrial DNA Variation
Authors: Glenn Travis C. , Stephan Wolfgang , Braun Michael J.
Published: March 2003

Abstract: The Whooping Crane (Grus americana) is an endangered bird that suffered a severe population bottleneck; only 14 adults survived in 1938. We assessed the genetic effect of this human‐caused bottleneck by sequencing 314 base pairs ( bp) of the mitochondrial DNA control region from cranes that lived before, during, and after this bottleneck. The maximum length of DNA amplifiable from museum specimens was negatively correlated with age, and only 10 of 153 specimens yielded the entire 314 bp sequence. Six haplotypes were present among the prebottleneck individuals sequenced, and only one of these persists in the modern population. The most common modern haplotype was in low frequency in the prebottleneck population, which demonstrates the powerful effect of genetic drift in changing allele frequencies in very small populations. By combining all available data, we show that no more than one‐third of the prebottleneck haplotypes survived the human‐caused population bottleneck. High levels of variation of substitution rates among nucleotide sites prevented us from estimating the prebottleneck population size. Our data will be incorporated into the captive breeding program to allow better management decisions regarding the preservation of current genetic diversity. These data offer the first glimpse into the genetic toll this species has paid for human activities.
Effects of Forest Fragmentation on Breeding Tanagers: A Continental Perspective
Authors: Rosenberg Kenneth V. , Lowe James D. , Dhondt André A.
Published: March 2003

Abstract:
We studied the effects of habitat fragmentation on four species of North American tanagers (  Piranga spp.) at 1107 study sites in 1995. Volunteer researchers used the standardized protocol of Project Tanager to select sites, census for breeding tanagers, and measure habitat and landscape features on a continental scale. In a principal components analysis, we used measures of forest patch size, distance to nearest other forest patches (isolation), percent forest cover and length of linear edge in a 1000‐ha landscape, and elevation. Our results showed that three independent habitat gradients affected tanager occurence: (1) overall amount of fragmentation; (2) forest configuration (the amount of edge in a landscape); and (3) elevation. Multiple logistic regression indicated significant variation among the tanager species in how habitat gradients affected tanager occurrence, presence of parasitic Brown‐headed Cowbirds (  Molothrus ater), and various nest predators. Scarlet, Western, and Summer Tanagers (  P. olivacea, P. ludoviciana, and P. rubra, respectively) responded similarly to the fragmentation gradient, with the probability of finding breeding tanagers dropping below 0.50 in highly fragmented sites. Response to the other habitat gradients was more variable, and effects on cowbirds and predators were usually opposite those of breeding tanagers (i.e., they were more common at highly fragmented sites). Response to habitat gradients also varied significantly among four regions within the range of Scarlet Tanagers. The strongest response to fragmentation, by breeding tanagers as well as by cowbirds and nest predators, was in the largely deforested Midwest and Atlantic Coast regions. In the heavily forested Northeast region, fragmentation had a significant but less severe effect on breeding tanagers. Effects were not significant in the Northern Forest region, where tanager abundance was low. Results of our continent‐wide study suggest that (1) forest fragmentation can be described similarly across most regions of North America; (2) three widespread tanager species exhibit clear and similar negative responses to habitat fragmentation; (3) local sensitivity to fragmentation varies geographically and may be lower in regions with greater overall forest cover; and (4) results from single‐species or local studies cannot be extrapolated to other species or regions. Conservation strategies to reverse the declines of forest bird populations will require knowledge of habitat requirements across the entire ranges of widespread species, as well as how demographic and landscape factors interact to create population sources and sinks.
Reciprocal Model for Meeting Ecological and Human Needs in Restoration Projects
Authors: Geist Cathy , Galatowitsch Susan M.
Published: March 2003

Abstract:Ecological restoration aims to reverse the losses of biodiversity and the degradation of ecosystems that have occurred through time as humans have affected landscapes. To date, however, restoration success has been limited, in spite of increasing ecological knowledge and technical skills. Technical constraints, although significant, are only part of the problem. The reasons for restoration failure, including cost constraints, limitations in land allocation, and insufficient time and labor, often involve underlying human obstacles. Unless such obstacles are overcome, ongoing commitment to restoration projects will likely remain limited. Because restoration involves diverse scientific and social interests and is often laden with conflicting priorities, we view it as a “wicked problem.” We examine ways commitment to restoration could be increased by developing beneficial relationships between humans and the natural environment in the context of restoration. We propose a model that shows that the ecological needs of the restoration area have the greatest potential to be met when human contributions are greatest. In turn, humans benefit increasingly as the restored ecosystem recovers. As human needs are addressed over time, their potential contributions to the restoration area increase. The extent to which contributions meet needs is enhanced or constrained by factors ranging from available technology and funding to community support. This ongoing loop of interactions between needs and contributions provides a basis for restoration planning and implementation which potentially reduces both ecological and human roadblocks to success. The model suggests that community‐based projects will be most successful when experts train the group in restoration decision making, when expertise and leadership are developed within the group, and when participants experience group cohesiveness and a sense of personal reward.
Population Demographics and Genetic Diversity in Remnant and Translocated Populations of Sea Otters
Authors: Bodkin J. L. , Ballachey B. E. , Cronin M. A. , Scribner K. T.
Published: March 2003

Abstract:The effects of small population size on genetic diversity and subsequent population recovery are theoretically predicted, but few empirical data are available to describe those relations. We use data from four remnant and three translocated sea otter ( Enhydra lutris) populations to examine relations among magnitude and duration of minimum population size, population growth rates, and genetic variation. Mitochondrial (mt)DNA haplotype diversity was correlated with the number of years at minimum population size (rs= −0.741,p= 0.038) and minimum population size (rs= 0.709,p= 0.054). We found no relation between population growth and haplotype diversity, although growth was significantly greater in translocated than in remnant populations. Haplotype diversity in populations established from two sources was higher than in a population established from a single source and was higher than in the respective source populations. Haplotype frequencies in translocated populations of founding sizes of 4 and 28 differed from expected, indicating genetic drift and differential reproduction between source populations, whereas haplotype frequencies in a translocated population with a founding size of 150 did not. Relations between population demographics and genetic characteristics suggest that genetic sampling of source and translocated populations can provide valuable inferences about translocations.
What It Will Take to Monitor Forest Elephant Populations
Authors: Walsh Peter D. , White Lee J. T.
Published: March 2003

Abstract: The decision by the Convention on International Trade in Endangered Species (CITES) to condition a limited sale of ivory on the status of elephant poaching has brought into sharp focus the technical, organizational, and financial challenges inherent in setting up a continent‐wide monitoring program. The task will be particularly arduous in central Africa, where forest elephant populations are difficult to monitor and the infrastructure necessary for population monitoring is lacking. The magnitude of effort that will be necessary is illustrated by an elephant survey done in the Gamba Complex, a network of protected areas on the southwest coast of Gabon. Implementing the survey required a large‐scale program for training Gabonese nationals in field survey and analysis methods necessary for elephant monitoring. Field work carried out during the training program suggests that a combination of reconnaissance and line transects can produce statistically valid population estimates for a substantially lower effort than line transects alone. We illustrate statistical frameworks for comparing the efficiency of alternative sampling methods, and we analyze the sensitivity of current survey methods, which can detect abundance changes on the order of 15%, given fairly high effort levels. Although these training and methodological results are encouraging, they are just small steps in a complex and ongoing process. We argue that this process has many parallels with what needs to be done if the international conservation community is to respond to the challenge set for it by the 1997 CITES meeting. There must be a concerted effort focused both on improving survey methods and on developing the human resources and on‐the‐ground infrastructure necessary to implement these methods.
Reliability of Conservation Actions Based on Elasticity Analysis of Matrix Models
Authors: Mills L. Scott , Doak Daniel F. , Wisdom Michael J.
Published: March 2003

Abstract: Matrix population models have entered the mainstream of conservation biology, with analysis of proportional sensitivities (elasticity analysis) of demographic rates becoming important components of conservation decision making. We identify areas where management applications using elasticity analysis potentially conflict with the mathematical basis of the technique, and we use a hypothetical example and three real data sets (Prairie Chicken [  Tympanuchus cupido], desert tortoise [Gopherus agassizii], and killer whale [Orcinus orca]) to evaluate the extent to which conservation recommendations based on elasticities might be misleading. First, changes in one demographic rate can change the qualitative ranking of the elasticity values calculated from a population matrix, a result that dampens enthusiasm for ranking conservation actions based solely on which rates have the highest elasticity values. Second, although elasticities often provide accurate predictions of future changes in population growth rate under management perturbations that are large or that affect more than one rate concurrently, concordance frequently fails when different rates vary by different amounts. In particular, when vital rates change to their high or low values observed in nature, predictions of future growth rate based on elasticities of a mean matrix can be misleading, even predicting population increase when the population growth rate actually declines following a perturbation. Elasticity measures will continue to be useful tools for applied ecologists, but they should be interpreted with considerable care. We suggest that studies using analytical elasticity analysis explicitly consider the range of variation possible for different rates and that simulation methods are a useful tool to this end.
A Quantitative Approach to Endangered Species Act Classification of Long‐Lived Vertebrates: Application to the North Pacif ic Humpback Whale
Authors: Gerber Leah R. , Demaster Douglas P.
Published: March 2003

Abstract: The U.S. Endangered Species Act (ESA) mandates that recovery plans include specific criteria to determine when a species should be removed from the List of Endangered and Threatened Wildlife. To meet this mandate, we developed a new approach to determining classification criteria for long‐lived vertebrates. The key idea is that endangerment depends on two critical aspects of a population: population size and trends in population size due to intrinsic variability in population growth rates. The way to combine these features is to identify a population size and range of population growth rates (where λ denotes the annual multiplicative rate of change of a population) above which there is a negligible probability of extinction. To do so, (1) information on the current population size and its variance is specified; (2) available information on vital rates or changes in abundance over time is used to generate a probability distribution for the population's λ; (3) the lower fifth percentile value for λ (denoted as λ(0.05)  ) is obtained from the frequency distribution of λs; and (4) if λ(0.05) is <1.0, a backwards population trajectory starting at 500 individuals for a period of 10 years is performed and the resulting population size is designated as the threshold for listing a species as endangered, or if λ(0.05) is ≥1.0, the threshold for endangerment is set at 500 animals. A similar approach can be used to determine the threshold for listing a species as threatened under the ESA. We applied this approach to North Pacific humpback whales ( Megaptera novaeangliae) and used Monte Carlo simulations to produce a frequency distribution of λs for the whales under three different scenarios. Using λ(0.05), it was determined that the best estimates of current abundance for the central population of North Pacific humpback whales were larger than the estimated threshold for endangered status but less than the estimated threshold for threatened status. If accepted by the responsible management agency, this analysis would be consistent with a recommendation to downlist the central stock of humpback whales to a status of threatened, whereas the status of eastern and western stocks would remain endangered.