bluuebunny/crossref_metadata_2025 huggingface dataset:
Six ecological factors that may limit African wild dogs, Lycaon pictus
Authors: Creel Scott , Creel Nancy Marusha
Published: February 2006

African wild dogs (Lycaon pictus) always live at low population densities relative to sympatric large carnivores. This suggests that there are basic ecological reasons for the wild dog's endangered status. We examined the effects of intraspecific and interspecific competition, infectious diseases, foraging success, genetics and human activities on wild dogs. We present data from wild dogs in the Selous Game Reserve, and make comparisons with other populations to identify the limiting factors that are broadly important. The high density of wild dogs in Selous (40 adults/1000 km2) is associated with weak competition from lions and spotted hyenas. Across ecosystems, population density is negatively related to the intensity of interference competition with larger carnivores. Predation by lions and hyenas accounted for 13% of known‐cause deaths in Selous and 33–50% in other populations. Intraspecific competition caused 69% of known‐cause deaths in Selous, through infanticide and fights between packs, although most of the victims were juveniles with low reproductive value. Infectious diseases had little apparent impact in Selous (4% of deaths) or Kruger National Park (5%), but did play a role in the extinction of a small population in Serengeti. Infectious diseases and competition will generally interact because competitors harbor and transmit the diseases that affect wild dogs. Human activities caused 12% of deaths in Selous, even though it is large (43 000 km2) and does not border large human or livestock populations. Humans were the major agent of mortality in some populations. Foraging success varied little across ecosystems and was not apparently limiting. Mitochondrial DNA (mtDNA) genotypes revealed clinal variation between Selous and distant populations (rather than geographically isolated subspecies, as previously suggested). All wild dog populations have a genetically effective size (Ne) less than 500, so gene flow is necessary to maintain genetic diversity within populations.
Population dynamics of the endangered Cape Sable seaside‐sparrow
Authors: Curnutt John L. , Mayer Audrey L. , Brooks Thomas M. , Manne Lisa , Bass Oron L. , Fleming D. Martin , Nott M. Philip , Pimm Stuart L.
Published: February 2006

The Cape Sable seaside‐sparrow (Ammodramus maritimus mirabilis) has disappeared from its only known breeding areas episodically since its discovery early this century. Systematic surveys across its range in the southern Everglades find the sparrow's range to be fragmented into six subpopulations. The sparrow population decreased by 58% between 1992 and 1995, with the near extinction of the western half of the population and the temporary local extinction of some eastern populations. Other similar grassland sparrows have populations that vary considerably from year to year. Yet the decline in the western subpopulation and the local extinction of some of the peripheral populations cannot be explained by natural variability alone. Hurricane Andrew passed over several subpopulations prior to the particularly poor year of 1993. However, the geographical and temporal patterns of subpopulation decline are not consistent with what would be expected following a hurricane. Frequent fires prevent successful breeding as does flooding during the breeding season. Better management can prevent frequent fires and episodic flooding. However, the long‐term survival of the sparrow depends on managing the unanticipated risks that attend its small, fragmented population.
Water levels, rapid vegetational changes, and the endangered Cape Sable seaside‐sparrow
Authors: Nott M. Philip , Bass Oron L. , Fleming D. Martin , Killeffer Stephen E. , Fraley Nancy , Manne Lisa , Curnutt John L. , Brooks Thomas M. , Powell Robert , Pimm Stuart L.
Published: February 2006

The legally endangered Cape Sable seaside‐sparrow (Ammodramus maritimus mirabilis) is restricted to short‐hydroperiod, marl prairies within Florida's Everglades National Park and Big Cypress National Preserve. Marl prairies are typified by dense, mixed stands of graminoid species usually below 1 m in height, naturally inundated by freshwater for 3–7 months annually. Water levels affect the birds directly, by flooding their nests, and indirectly by altering the habitat on which they depend. Managed redistribution of water flows flooded nearly half of the sparrow's geographical range during several consecutive breeding seasons starting in 1993. Furthermore, these high water levels rapidly changed plant communities, so jeopardizing the sparrow's survival by reducing the availability of nesting habitat.
Osteological corroboration of pathological stress in a population of endangered Florida pumas (Puma concolor coryi)
Authors: Duckler Geordie L. , Van Valkenburgh Blaire
Published: February 2006

The Florida panther, Puma concolor coryi, is a subspecies on the verge of extinction. Recent field studies have shown the dwindling population to be suffering from numerous physical problems manifest in their soft tissues. Here we explore the skulls and skeletons of more than 50 P. concolor coryi for corroborative evidence of poor condition such as tooth fracture, arthritis, infection, trauma, and lines of arrested growth (Harris lines). Results are compared with those for an osteological collection of presumed healthy pumas from outside Florida. Although the two samples did not differ significantly in the relative prevalence of most of the pathologies, the Florida cats fractured their teeth more often and exhibited significantly more lines of arrested growth in their long bones. The greater number of teeth broken in life is associated with heavier tooth wear among Florida panthers and a diet depauperate in large prey. The elevated incidence of Harris lines is probably a result of more regular episodes of poor nutrition in the Florida population. Our results demonstrate that the study of osteopathologies is a new tool for the conservation biologist and highlight the value of preserving entire skeletons, as has been done for P. concolor coryi.
Estimating the demographic effective population size of the Saimaa ringed seal (Phoca hispida saimensis Nordq.)
Authors: Kokko Hanna , Lindström Jan , Ranta Esa , Sipilä Tero , Koskela Jouni
Published: February 2006

A common ‘rule of thumb' in conservation biology is that populations of more than 100 individuals are not threatened by demographic stochasticity alone. However, the effect of demographic stochasticity on population survival may be strengthened if the population has a non‐homogeneous demography. A recently developed measure, the demographic effective population size ND, scales population size by taking the differential contribution of individuals into account. We exemplify the estimation of ND with the current population of the Saimaa ringed seal, comprising about 200 individuals. The estimate of ND is shown to be dependent on how independently individuals can be assumed to reproduce. Completely independent reproduction leads to ND∼ 250, suggesting a safe future for the population. However, when acknowledging the potential of breeding failure due to habitat limitation and difficulties of dispersal among the different subareas of Lake Saimaa, ND lies in an alarming range from six to 30 individuals. The effective means to increase the ND value are limited. Although subdivision itself decreases the value of ND, improving dispersal of individuals is shown to be of limited aid. Instead, the most effective way to enhance future prospects of the Saimaa seal population is to improve pup survival to maturity.
Description of Muntiacus truongsonensis, a new species of muntjac (Artiodactyla: Muntiacidae) from Central Vietnam, and implications for conservation
Authors: Giao P. M. , Tuoc D. , Dung V. V. , Wikramanayake E. D. , Amato G. , Arctander P. , MacKinnon J. R.
Published: February 2006

A small blackish muntjac has been discovered in the west Quang Nam province of Vietnam. DNA sequencing of six individuals showed that this is a distinct species. A description is given. The new find is the third new ungulate species to be discovered in Vietnam in five years. The paper predicts that more species remain to be found in the Annamite mountain range and includes DNA analysis from two more undescribed species. The DNA analysis indicates that there has been a radiation of several related muntjac species in the Annamite mountains, also that the new truongson muntjac shows high intraspecific genetic diversity indicative of a large effective population size. The paper discusses the significance of these finds from an evolutionary and conservation viewpoint. The authors urge conservation authorities in the IndoChinese countries to devote special measures to protect this site of dynamic evolution which retains a combination of relict endemics (e.g. Pseudoryx) as well as on‐going speciation.
A new species of muntjac, Muntiacus putaoensis (Artiodactyla: Cervidae) from northern Myanmar
Authors: Amato George , Egan Mary G. , Rabinowitz Alan
Published: February 2006

A new species of barking deer (Muntiacus spp.) is described from northern Myanmar. Diagnostic DNA character data are presented along with preliminary information on morphology, distribution, and phylogenetic relationships. This discovery contributes significantly to our knowledge of this poorly studied group and highlights the importance of continued field surveys in remote regions. Similar studies have resulted in a significant increase in conservation efforts in other parts of South‐east Asia, and argue for additional conservation efforts for this region.
Male‐producing thermal ecology of a southern loggerhead turtle nesting beach in Brazil: implications for conservation
Authors: Baptistotte Cecília , Scalfoni Juarez T. , Mrosovsky N.
Published: February 2006

The major nesting areas for loggerhead turtles in Brazil are estimated to produce about 90% female hatchlings on account of their warm temperatures. In the present study, sand temperatures were monitored at the southern cooler end of the nesting range (Comboios, Espiríto Santo): the temperatures were cool enough to produce a far greater proportion of males than at the major beaches further north. Particular beaches may be thermally suited for the production of a particular sex. Protection of rookeries that appear minor in terms of numbers of turtles nesting could be important for the health of a larger population by insuring that there is an appropriate sex ratio. Temperatures were also monitored in a central guarded hatchery, set back from high seas. The hatchery was thermally similar to zones on the beach where turtles commonly lay, indicating that this conservation practice is unlikely to introduce any large distortions of sex ratio on this beach.
Comparison of the population viability analysis packages GAPPS, INMAT, RAMAS and VORTEX for the whooping crane (Grus americana)
Authors: Brook Barry W. , Cannon John R. , Lacy Robert C. , Mirande Claire , Frankham Richard
Published: February 2006

Population viability analysis (PVA) is widely used in conservation biology to compare management strategies and predict probabilities of extinction for endangered species. However, it remains unclear whether the available range of generic PVA programs produce similar predictions when applied to common data sets. A comparative analysis was carried out using six commonly applied PVA packages (GAPPS, INMAT, RAMAS Age, RAMAS Metapop, RAMAS Stage and VORTEX), based on the extensive population data available for the endangered whooping crane, Grus americana. Significant differences were found between the projections of the PVA packages. In particular, the introduction of stochastic variation in breeding structure led to large differences between some packages. Surprisingly, two versions of VORTEX produced very different predictions due to a subtle difference in the way monogamous breeding was modelled. The pattern of similarities and differences among the projections of the packages differ depending on the species examined. In contrast to the predictions of comprehensive (realistic) models, simplified (standardized) models were found to be relatively congruent, which probably reflects similarities in the fundamental biological processes being modelled by the PVA packages. The implications for conservation are clear; caution must be exercised when interpreting the projections of a model built using any one PVA package since, due to seemingly subtle differences in what biological assumptions and threatening processes are included in the models, the predictions among PVA packages (or versions of the same program) are not necessarily concordant.
Microsatellites identify introduced New Zealand tammar wallabies (Macropus eugenii) as an ‘extinct’ taxon
Authors: Taylor A. C. , Cooper D. W.
Published: February 2006

The range of the tammar wallaby (Macropus eugenii) has decreased substantially in Australia in recent times. Because two introduced populations in New Zealand may have descended from a now‐extinct Australian population(s), we investigated their origins using a novel approach. We combined data from seven highly polymorphic microsatellite markers with simulation modelling to infer the history and conservation value of the New Zealand populations. The microsatellite alleles in one New Zealand population (Rotorua) are merely a subset of those in the other (Kawau Is.), suggesting Rotorua had no immigrants from an independent source. However, in the Kawau Is. population (sample size 33–37), 37 alleles were absent that were present in the Kangaroo Is. (South Australia) population at frequencies ranging from 1–40%. The probability of those alleles being lost during a founding event from Kangaroo Is. was investigated using a program that simulates the genetic consequences of population size bottlenecks. Use of realistic bottleneck parameters resulted in probabilities approaching zero that the observed allele deficiencies in the Kawau population could have occurred randomly, identifying the New Zealand tammar wallabies as descendants of a distinct taxon that is no longer extant in Australia.
Identification of domestic cattle hybrids in wild cattle and bison species: a general approach using mtDNA markers and the parametric bootstrap
Authors: Ward Todd J. , Bielawski Joseph P. , Davis Scott K. , Templeton Joe W. , Derr James N.
Published: February 2006

Many species are currently undergoing reductions in population size due to widespread habitat loss and expanding human activities. Because interspecific hybridization is often a consequence of population decline and fragmentation, identification of individuals or populations with hybrid ancestry is an increasingly important issue in conservation biology. In many wild cattle and bison species, the problem of natural hybridization has been compounded by indiscriminate crossbreeding with domestic cattle for the purpose of improving domesticated stocks. Therefore, a genetic test using the polymerase chain reaction was developed so that wild cattle and bison with domestic cattle mitochondrial DNA (mtDNA) haplotypes could be rapidly identified. Using this genetic test, domestic cattle mtDNA haplotypes were detected in Bos grunniens (yak), Bison bonasus (European bison), and 6 out of the 15 (40%) Bison bison (North American bison) populations tested. In total, 30 out of the 572 (5.2%) North American bison tested, were found to have domestic cattle mtDNA. The hybrid origin of these mtDNA haplotypes was verified in a phylogenetic analysis using the parametric bootstrap. These results are discussed in terms of their implications for the conservation status and future management of wild cattle and bison species.
Biological and technical considerations of carnivore translocation: a review
Authors: Miller Brian , Ralls Katherine , Reading Richard P. , Scott J. Michael , Estes James
Published: February 2006

Carnivore translocations are usually risky and expensive, and a number of biological and non‐biological factors can influence success. Biological considerations include knowledge of genetics, demographics, behavior, disease, and habitat requirements. This information is critical for determining if the translocation should be attempted, if it could be successful, and how it could be implemented in an efficient and effective manner. We stress that individual species will vary in their responses, and ideas should be tested scientifically. The technical considerations of translocation are closely related to the biological questions. They include legal framework, fiscal and intellectual resources, monitoring capacity, goals of the translocation, logistic challenges, and organizational structure of decision‐making. We do not discuss socio‐economic aspects of translocation because those challenges require detailed discussion in a separate paper. We suggest that because large carnivores often play key roles in regulating ecological interactions between trophic levels, restoring them is more than a single‐species activity. By restoring carnivores in viable numbers, we can take a large step toward recovering ecological integrity of geographically extensive landscapes.
Belding's yellowthroat: current status, habitat preferences and threats in oases of Baja California, Mexico
Authors: Rodríguez‐Estrella Ricardo , Delgado Laura Rubio , de Bonilla Esteban Pineda Diez , Blanco Guillermo
Published: February 2006

The Belding's yellowthroat (Geothlypis beldingi) is an endemic species of Baja California Sur confined to the edge vegetation of freshwater at several oases. Information on its current status, distribution and habitat selection, and an analysis of the human‐related threats that the species faces at 10 oases are given here. Belding's yellowthroats have disappeared from three historical sites, Santiago, Miraflores and El Triunfo, where they were recorded in the early 1900s. Belding's yellowthroats forage mainly in reed grass and cattails in all oases and were never recorded > 50 m outside the edge vegetation of the water. The main threats we detected to their habitat were cutting of reed grass for rural home construction, burning vegetation, opening trails to the water for cattle, overgrazing of reed grass by horses and burros, and using up the water for agricultural and tourism purposes. Although local populations of the species seem to be common, they are vulnerable because the distribution of the species in southern Baja California is patchy. Populations are in general small and isolated, the bird has habitat‐specific requirements, and human‐related activity is putting pressure on the habitat of this endemic species. A Multidimensional Scaling Analysis showed that southern populations are likely to be more severely affected than northern ones.
Microsatellite heterozygosity, fitness and demography in natterjack toads Bufo calamita
Authors: Rowe G. , Beebee T. J. C. , Burke T.
Published: February 2006

Relationships between mean individual fitness and genetic heterozygosity remain controversial because multiple studies over many years have yielded inconsistent results. However, molecular measurements of genetic variation have mostly been based on allozyme markers, which may have substantial limitations due to their relative insensitivity and occasionally also to the effects of natural selection. We investigated variation in the number of tandem dinucleotide repeats at eight polymorphic microsatellite loci in 38 natterjack toad, Bufo calamita, populations that varied in census size, degree of isolation and distance from the distributional range edge. We also measured fitness attributes, notably larval survival and growth rates, under standardized conditions using samples from six of these populations. The results indicated that larval growth rates were positively and strongly correlated with expected heterozygosity (He) across the microsatellite loci. He was in turn highest in large populations with minimal isolation, but low near the biogeographical range edge irrespective of population size. Larvae from the smallest and most isolated natterjack population exhibited particularly low fitness and heterozygosity. Our results suggest that microsatellite loci may provide a valuable new approach in studies of links between fitness and heterozygosity.
Protected areas and the conservation of grouse, partridges and pheasants in east Asia
Authors: McGowan Philip , Chang‐qing Ding , Kaul Rahul
Published: February 2006

Grouse, partridges and pheasants belong to the highly threatened avian order Galliformes. We collected together existing data on the distribution of these species in east Asia (China and Pakistan south and east to the Lesser Sundas in Indonesia and Palawan in the Philippines) from published and unpublished sources. From this we extracted 1068 records of 101 east Asian endemics (plus three other species that have been found in east Asian protected areas) in 369 protected areas. One species was found in 108 protected areas and a further two in 39 and 38 protected areas: six species were not known from any. Of the threatened endemics, 84% were recorded in 10 or fewer protected areas compared with 50% of endemic species that are non‐threatened. A near‐minimum network designed to include each species in three protected areas wherever possible comprised 49 irreplaceable sites and 33 others. Comparison with other studies should indicate which of these protected areas are also important for other groups of organisms, such as plants and swallowtail butterflies. There is a need for improvement in knowledge of occurrence in protected areas. This should be provided from further collation of existing information and from undertaking targeted surveys. There is also a need to consider which protected areas are suitable for inclusion in a network and how many such areas are required to ensure that each species is adequately represented.
Translocations and rapid evolutionary responses in recently established populations of western mosquitofish (Gambusia affinis)
Authors: Stockwell Craig A. , Weeks Stephen C.
Published: February 2006

The response of quantitative traits in translocated populations has not been well explored. Evolutionary shifts in quantitative traits, such as life history characteristics, are of particular interest because of their obvious association with fitness. In a recent survey, Stockwell (1995) examined life history variation of four populations of western mosquitofish (Gambusia affinis) that were derived from a common ancestral population 55–58 years earlier. Three life history traits differed considerably among the four sites and appeared to be correlated with local environmental conditions. To test whether these differences were due to plasticity or rapid evolution, fish from the four sites were maintained under common‐garden conditions for two generations. After two generations a genetic basis was inferred for two of the three traits (size at maturity and fat content), but not for the third trait (offspring size). Thus, rapid evolution had occurred for two life history traits in these recently established populations. This case of rapid life history evolution may be due to genetic drift and/or natural selection. These data suggest that translocations may lead to rapid evolutionary responses of targeted taxa. Rapid evolutionary responses are of special concern for ‘refuge’ populations that are maintained as a hedge against extinction.
Modelling the distribution of red squirrels (Sciurus vulgaris) on the Isle of Wight
Authors: Rushton S. P. , Lurz P. W. W. , South A. B. , Mitchell‐Jones A.
Published: February 2006

We investigated the distribution of red squirrel (Sciurus vulgaris) populations on the Isle of Wight using Generalized Linear Models (GLMs) and a spatially explicit population dynamics model (SEPM) with the aim of identifying management options for red squirrel conservation. The presence/absence of red squirrels in habitat blocks in the landscape was used as the dependent variable and the size and separation of habitat blocks as independent variables in the GLM analysis. Red squirrel presence within a woodland was significantly related to woodland size and the distance to the nearest wood known to contain squirrels. The SEPM‐generated predictions on population viability were closest to the field data when a low dispersal distance of 1 km was used. This suggests that squirrel dispersal on the Isle of Wight is restricted. Our results suggest that some large interconnected woodlands should be maintained if red squirrels are to be conserved for the future.
Testing for inbreeding and outbreeding depression in the endangered Gila topminnow
Authors: Sheffer Ruby J. , Hedrick Philip W. , Velasco Anthony L.
Published: February 2006

The extent of inbreeding and outbreeding depression is thought to be a fundamental factor influencing the long term persistence of an endangered species. However, there have been no comprehensive examinations of either factor in an endangered species, except for a mouse species. Here we examined both the extent of inbreeding and outbreeding depression for five traits related to fitness in populations from the four watersheds in which the endangered Gila topminnow (Poeciliopsis o. occidentalis) still exists in the USA by making experimental matings with replicate samples and simultaneous controls. There was generally high survival, similar body size, and little bilateral asymmetry for all the inbred and outbred matings for all populations, i.e. there was no evidence of either inbreeding or outbreeding depression for these traits. Similarly there was no evidence of inbreeding or outbreeding effects for fecundity or sex ratio except for the sample from Monkey Spring, which had highly skewed (female‐biased) sex ratios after one generation of inbreeding. In addition, brood sizes for Sharp Spring declined over time in inbred lines maintained by full‐sib mating. These results further support the suggestion, based on molecular genetic analysis and considerations of habitat differences, that Monkey Spring be considered an evolutionarily significant unit, distinct from the remainder of existing populations. Potential explanations for the results and their implications for conservation are discussed.
Detecting inbreeding depression is difficult in captive endangered species
Authors: Kalinowski Steven T. , Hedrick Philip W.
Published: February 2006

During the past two decades, pedigree analysis has documented inbreeding depression in many captive populations. This and subsequent research has led to a recognition that inbreeding depression is a potentially important determinate of small population fitness, in both captivity and the wild. Modern captive‐breeding programmes now universally avoid inbreeding. We use simulation to investigate how much traditional pedigree analysis will reveal about the effect of inbreeding in such populations. We find that pedigrees typical of breeding programmes designed to avoid inbreeding have low statistical power to detect inbreeding depression.
How many to dehorn? A model for decision‐making by rhino managers
Authors: Milner‐Gulland E. J.
Published: February 2006

A stochastic dynamic programming model is presented for decision‐making by the manager of a small rhino reserve facing a poaching threat, with the objective of maximizing the rhino population size in the long term. The manager decides annually what proportion of the budget to spend on dehorning as opposed to law enforcement. Poacher incentives depend on revenues from illegal horn sales, which are related to the manager's decisions through the mean horn size of the rhino population (affected by spending on dehorning). Poacher incentives also depend on hunting costs, which are related to the manager's decisions through the risk of capture and punishment (affected by spending on law enforcement). The results suggest that, at realistic parameter values, the optimal strategy is to dehorn as many rhinos as possible annually except at very low rhino population sizes, budgets or mean horn sizes. The simple strategy of dehorning annually regardless of population size or mean horn size gives very similar results to the optimal strategy. Other potential strategies (such as dehorning only half the rhinos each year) performed badly. Selling horns and reinvesting the proceeds in rhino conservation did not provide enough revenue to significantly increase rhino population sizes.
Retention of reproductive barriers and ecological differences between two introduced sympatricMacropusspp. in New Zealand
Authors: Taylor A. C. , Sunnucks P. , Cooper D. W.
Published: February 2006

In their native Australia, tammar (Macropus eugenii) and parma (M. parma) wallabies are allopatric and differ markedly in habitat use, social structure and degree of reproductive synchrony. They occur sympatrically only on Kawau Is., New Zealand, as a result of introductions last century. Reproductive data collected from wallabies on Kawau Is. in April 1996 show thatM. eugeniimaintains high reproductive synchrony whileM. parmaremains asynchronous. Both species show sexual dimorphism and differences in habitat use as seen in Australia. In additionM. parmais more solitary, and is frequently found in closed‐canopy woodland, whileM. eugeniitends to aggregate in open grassy clearings. Thus the species maintain broad reproductive and biological distinctions, despite enforced sympatry in a novel environment. Highly‐resolving genetic (microsatellite) data reveal no evidence for hybridization. This is essential information given the known (M. eugenii) or likely (M. parma) high conservation value of New Zealand stocks. Kawau Is. is the only predator‐free site withM. parma, a species whose persistence in Australia is threatened by fox predation. Finally, we use data on mitochondrial cytochromebsequence divergence amongst severalMacropustaxa to demonstrate close agreement with degree of reproductive isolation.
Conservation of the greater glider (Petauroides volans) in remnant native vegetation within exotic plantation forest
Authors: McCarthy Michael A. , Lindenmayer David B.
Published: February 2006

A field‐validated metapopulation model of patch occupancy was used to examine the persistence of greater gliders (Petauroides volans) in patches of remnant native eucalypt forest in south‐eastern Australia. The model was based on a system of eucalypt patches embedded within a plantation forest of exotic radiata pine (Pinus radiata) at Buccleuch State Forest, New South Wales. The probability of local extinction in occupied patches was a function of patch size. The probability of colonization of empty patches was a function of the size and proximity of occupied patches. The results of the simulations suggested that suitable habitat should occupy approximately 10% (or more) of the total landscape to ensure the persistence of greater gliders. Rates of patch occupancy were maximized when suitable habitat was clustered into larger patches. Patches <3 ha in area were predicted to be of limited value as habitat for greater gliders. The predictions of the model are consistent with the observed persistence of greater gliders in the eucalypt patch system. The system of unlogged eucalypt patches within the pine plantation is a useful model of a network of small to medium‐sized conservation reserves. Principles of reserve design can have value even in somewhat degraded and highly modified landscapes. The results demonstrate that reserved patches of native forest embedded within intensively logged forest can have significant conservation value, with important implications for the design and establishment of new softwood plantations.
Deforestation and bird extinctions in the Atlantic forest
Authors: Brooks Thomas , Tobias Joe , Balmford Andrew
Published: February 2006

The Atlantic forests of South America hold a great concentration of biodiversity, but most of this habitat has been destroyed. We therefore expect many species to become extinct, and yet no bird extinctions have conclusively been recorded. There could be three explanations for this. First, birds may be able to adapt to deforested landscapes. Second, many species may have become extinct before they were known to science. Third, there may be a time‐lag following deforestation before extinction occurs. We present the most complete list to date of the endemic birds of the Atlantic forests (124 forest‐dependent species), and then use the species–area relationship to predict how many species we expect to become extinct through deforestation (51 species i.e. 41%). We also count how many Atlantic forest endemic birds are independently considered ‘threatened’ with ‘a high risk of extinction in the wild in the medium‐term future’ (45 species i.e. 36%). We compare these totals and find that they are similar, suggesting that there is a time‐lag between deforestation and extinction. We go on to test the robustness of this result by varying the parameters used to make our predictions. The only parameter that varies enough to substantially weaken predictions based on deforestation is the habitat classification of Atlantic ‘forest’ birds. If we include species that can survive in secondary and non‐forest habitats then, unsurprisingly, we find that deforestation overestimates threat. Overall, not only does deforestation accurately predict threat to Atlantic forest endemic birds, but this result is robust enough to accommodate considerable variability within our data.
Assessing population structure at high levels of differentiation: microsatellite comparisons of bighorn sheep and large carnivores
Authors: Forbes Stephen H. , Hogg John T.
Published: February 2006

Use of a new class of molecular marker for evolutionary or conservation studies may promise improved information, but it may also call for reassessment of analytical methods and empirical limitations. We used DNA microsatellites to study population structure in Rocky Mountain bighorn sheep (Ovis canadensis canadensis) and to test the ability of microsatellites to distinguish bighorn subspecies. Genetic differentiation between bighorn populations was dramatically greater than in comparable studies of brown bears and grey wolves, and these species differences are consistent with known differences in habitat use and dispersal. In bighorn, however, statistical limitations make it difficult to distinguish between moderately and highly divergent populations. As a result, only gene flow estimates greater than about one migrant per generation (OMPG) are informative about true population relatedness. In bears and wolves, apparent differentiation is so low that migration estimates are greater than OMPG continent‐wide, but factors other than high gene flow may contribute to these patterns. Despite analytical difficulties at large geographical scales and large genetic divergences, microsatellite data assist management by characterizing historical rates and patterns of dispersal on smaller scales, and by detecting population bottlenecks and regions of particularly high or low historical gene flow.
Do population size bottlenecks reduce evolutionary potential?
Authors: Frankham Richard , Lees Kelly , Montgomery Margaret E. , England Phillip R. , Lowe Edwin H. , Briscoe David A.
Published: February 2006

Single locus neutralist models predict that population size bottlenecks will reduce genetic variation and increase inbreeding, thereby reducing evolutionary potential. However, experimental evaluations of the effects of bottlenecks on quantitative genetic variation do not always follow predictions, especially for characters related to reproductive fitness. Populations of Drosophila melanogaster were subjected to population bottlenecks of a single pair for one or three generations, and their ability to tolerate increasing concentrations of NaCl was compared with those of their outbred base populations, and related highly inbred lines. Bottlenecked populations became extinct at significantly lower concentrations of NaCl than their non‐bottlenecked base populations. Population bottlenecks should be avoided in managing species of conservation concern.
Reproductive seasonality in the female scimitar‐horned oryx (Oryx dammah)
Authors: Morrow C. J. , Wildt D. E. , Monfort S. L.
Published: February 2006

Faecal oestrogen and progestin analyses were used to assess ovarian activity in non‐pregnant scimitar‐horned oryx (Oryx dammah) during a 13‐month interval. Mean (± SE) luteal phase, interluteal phase and oestrous cycle duration were 18.8 (± 0.5), 5.1 (± 0.2) and 23.8 (± 1.3) days, respectively. All females exhibited a synchronized anovulatory period that ranged from 36–95 days during spring. Short ovarian cycles (10.6 (± 0.8) days) were observed intermittently throughout the year and before the spontaneous resumption of oestrous cyclicity. Periovulatory peaks in oestrogen concentrations were detected for 42.5% (31/73) of ovarian cycles. A parallel analysis of reproductive data from the North American studbook (1985–1994) revealed that captive‐held scimitar‐horned oryx gave birth throughout the year. Sex ratio at birth was male‐biased (54.4%), and 19.1% of all calves failed to survive to 6 months of age (220 out of 1149 births). Only 0.7% of births resulted in twins. Median interbirth interval was 277 days, and 75% of these intervals were less than 332 days. Interbirth interval was extended (P < 0.05) if parturition occurred from January through May. In summary, the scimitar‐horned oryx is a seasonally polyoestrous species that experiences a distinct anovulatory period during spring in north‐east America.
Reintroduction programmes: genetic trade‐offs for populations
Authors: Earnhardt Joanne M.
Published: February 2006

Reintroductions of captive‐managed animals are a vital tool for the conservation of populations and species extinct in the wild. Because genetic diversity may impact population persistence, the genetic composition of reintroduced and captive populations is critical. For captive‐managed species with known pedigrees, individual animals can be selected to create reintroduced populations with specific genetic compositions. Five genetic and demographic strategies for selecting animals were tested on four species. Selection strategies were based on criteria identified in field and theoretical studies. Simulated reintroductions of animals from captive‐breeding programmes created a genetic conflict. Among the different strategies, increases in the genetic diversity of one subpopulation were negatively correlated with changes in the genetic diversity of the other subpopulation. For example, the release of genetically over‐represented animals was the most beneficial strategy for a captive‐breeding programme, but provided the least genetic diversity for the reintroduced population. However, gains and losses in genetic diversity between populations varied with different selection criteria and different population structures. Because captive‐breeding histories vary for each species, changes in genetic composition cannot be accurately predicted and no one strategy is universally optimal. Thus, genetic trade‐offs must be assessed for each population relative to specific programme goals.
Culling and the dynamics of the Kruger National Park African elephant population
Authors: van Aarde Rudi , Whyte Ian , Pimm Stuart
Published: February 2006

South Africa's National Parks Board has opted to control African elephants (Loxodonta africana) through culling in the Kruger National Park (KNP). Killing elephants is highly controversial. The Board must balance this controversy against the probable destruction of vegetation and the consequent depletion of biological diversity that high elephant densities cause. Annual aerial counts provided the population estimates on which the culling quotas were based. For management purposes, the elephant population of the Park is divided into four sub‐populations. From 1984 to 1994, the annual quota was usually taken from only one of these sub‐populations during a given year. This resulted in 3 to 5 years elapsing between culls in each sub‐population. We investigated the year‐to‐year changes in densities after culling. These changes were density dependent. Density dependence implies that immediate culls following estimated high densities may be premature. If left alone, the densities would decline naturally. Indeed, culling becomes self‐reinforcing as it moves population densities towards the level where reproduction is greatest. Data confirm this intuition: at densities greater than 0.37 elephants/km2 elephant numbers generally declined without culling. Many culls were unnecessary. Culling, as implemented in the past, may have had consequences for elephants and their habitat that were different to those expected from a mere reduction in their numbers. Densities in the year immediately after a cull tended to decline – not increase as would be expected from density dependence alone. Undoubtedly, this unexpected decline was the consequence of disturbance and subsequent emigration. In following years, the densities rose as animals moved back into the sub‐population. A management programme where culling will be instituted only when densities exceed 0.37 elephants/km2 in selected regions in the park for at least 1 year, may be more acceptable than the programme used up to 1995. However, we do not know if the vegetation of KNP can withstand the resulting episodic high densities. With densities presently exceeding the cut‐off values calculated for both the south and the northern management regions vegetation changes there need to be monitored.
Effects of southern flying squirrels Glaucomys volans on red‐cockaded woodpecker Picoides borealis reproductive success
Authors: Laves Kevin S. , Loeb Susan C.
Published: February 2006

Anecdotal data gathered from many populations suggest that southern flying squirrel (SFS, Glaucomys volans) use of the endangered red‐cockaded woodpecker's (RCW, Picoides borealis) nest and roost cavities may negatively affect RCW populations. We conducted a controlled experiment to determine the effects of SFSs on RCW reproductive success. During the 1994 and 1995 breeding seasons, SFSs were removed from 30 RCW clusters and 32 clusters served as controls. SFSs were the most frequently encountered occupants of RCW cavities and used 20–33% of RCW cavities in control and treatment clusters over both years. Treatment groups produced significantly more successful nests (≥ 1 fledgling) than control groups in 1994. In 1995 however, there was no difference in the number of successful nests. In both years, RCW groups nesting in treatment clusters produced significantly more fledglings than groups in control clusters in each of four experimental areas, averaging approximately 0.7 additional fledglings per nesting group. Loss of entire clutches or broods, possibly as a result of predation or abandonment, was a major factor limiting reproduction in control groups in 1994. In contrast, differences in partial brood loss appeared to be the cause of differential fledging success in 1995. Usurpation of RCW roost cavities by SFSs may have placed greater energetic demands on RCWs for cavity defence or thermoregulation, thus reducing energy available for reproduction. Our results show that SFS use of RCW cavities during the breeding season has a significant impact on RCWs and that management of RCW populations should include activities that either minimize SFS populations in RCW clusters or limit access of SFSs to RCW cavities.
Conservation monitoring: estimating mammal densities in woodland habitats
Authors: Caro T. M.
Published: February 2006

Conservation and ecological monitoring programmes often estimate animal densities over time, but in wooded and forested areas practical techniques are still poorly developed. Here I have examined five simple methods of deriving densities of large and medium‐sized mammals using line transects driven through miombo woodland habitat in Africa. These methods calculated area by dividing the number of individuals seen by (i) an average of each species' sighting distances, (ii) a fixed 200 m belt width, (iii) the area visible from the centre of the transect, (iv) visible area weighted by species' vegetation preferences, and (v) by dividing the number of groups seen by area visible from the transect. Individual‐based methods produced quite divergent estimates of species' densities and overall biomass with belt transects giving the lowest values. The group method and corresponding individual‐based method gave similar values, however. Most of these calculations yielded considerably higher density estimates than aerial surveys conducted in the same area over a similar time period. Sightings of species were not distributed evenly across vegetation types although the majority of mammal species were observed more often in open habitat. These findings indicate that ground‐based conservation monitoring programmes should set transects through several vegetation types, restrict comparisons to those studies that use the same methodology, and refrain from comparing ground and aerial surveys.
Effective population sizes: missing measures and missing concepts
Authors: Crandall Keith A. , Posada David , Vasco Dan
Published: February 2006

Genetic diversity within a population is a critical parameter for conservation biologists to assess. One approach for examining genetic diversity is through the determination of effective population sizes. Animal Conservation recently published a review of genetic approaches for estimating effective population sizes. We felt this review was incomplete both methodologically and conceptually. Here we extend that review to include coalescent‐based approaches for estimating effective population sizes. We then discuss different kinds of effective population sizes, including inbreeding, variance and eigenvalue effective sizes.
Experimental tests of minimum viable population size
Authors: Reed David H. , Bryant Edwin H.
Published: February 2006

Fitness and rates of extinction were compared among populations of the housefly, Musca domestica L., kept either at constant effective sizes of 50, 500 or 1500 or passed through extreme founder events reducing effective size to 5. Populations were maintained for 24 generations, which for small to medium‐sized mammals would be less than the 200 years suggested by Souléet al. (1986) as necessary for maintaining viable populations of endangered species. The results demonstrate that effective population sizes have to be greater than the 50 individuals suggested by Franklin (1980) to retain fitness and escape extinction, even in the short term. In contrast to populations of constant size that exhibited monotonic decreases in fitness through time, populations established with few founders rebounded from initial inbreeding depression. However, they were less adaptable to environmental stress than constant size populations, suggesting that populations founded with few numbers may do well within a single environment but may do far less well if they are reintroduced to natural environments or exposed to rapid environmental changes.
Taxonomic homogenization of the global avifauna
Authors: Lockwood Julie L. , Brooks Thomas M. , Mckinney Michael L.
Published: February 2006

Biotic homogenization is seen as the consequence of preferential loss of native species followed by ecological replacement with widespread exotics. Homogenization is not random in its effects on higher taxa. Using Monte Carlo simulations (rather than binomial statistics) we find taxonomic patterns in the risk of extinction and probability of successful introduction among birds. Sixteen avian families selectively contain extinct or threatened birds. Eight avian families selectively contain successfully introduced birds. Eight of these 24 taxonomically selected families have not been identified in previous studies, presumably because they are species‐poor. The 22 living taxonomically selected families are classified into four homogenization categories. These categories reflect how extinction and invasion are combining in their effects at the family level. Range size, as indexed by island endemism, and human influence are the primary forces driving taxonomic homogenization patterns among birds. There is no evidence that evolutionary age influences homogenization patterns. Phylogenetic comparative analyses, which explicitly recognize the role of human influence, are needed to elucidate more detailed ecological correlates to homogenization trends.