Rate Of Population Decline Research Articles

Distribution and conservation ofGrallariaandGrallariculaantpittas (Grallariidae) in Ecuador

SummaryThe current ranges of many tropical species of conservation concern are poorly known, yet this information is critical for assessing their conservation status against the IUCN Red List criteria and implementing species-level management. Antpittas in the generaGrallariaandGrallariculaare elusive, ground-foraging insectivores, highly susceptible to a range of threats. For these genera, we combine environmental niche modelling with expert knowledge in order to predict species’ geographic distributions, and we use current estimates of deforestation to evaluate their conservation status in Ecuador. We use BIOCLIM to generate a first pass geographic prediction, which was further aided by expert knowledge of their natural history. This methodology allowed us to assess the conservation status of each species, revising previous assessments at the national level and making recommendations for revision of global IUCN Red List categories. Based on inferred rates of population decline, derived from estimates of loss of suitable habitat, we suggest ranking three species as ‘Endangered’ in Ecuador, one as 'Vulnerable', and three as ‘Near Threatened’. Predicted national ranges vary in size from 56.05 km2to 112,745 km2. Patterns of range loss were different for each Andean slope, with higher deforestation on the western slope. The combination of niche modelling and knowledge of habitat loss can be a powerful tool to aid conservation efforts in the face of a poor understanding of population demographics, as is the case for many Neotropical taxa. We hope the methodology and results provided here will increase our understanding, and focus future attention on the conservation of this poorly known avian group.

Late 19th Century Abundance Trends of the Eskimo Curlew on Nantucket Island, Massachusetts

Abstract. The Eskimo Curlew (Numenius borealis), now near extinction, was intensively hunted during fall migration along the Atlantic coast from Labrador to Long Island through the late 19th century. Scores of post-1850 records from this region have been gleaned from the literature but the rate of population decline has never been assessed. George H. MacKay's shooting journal, which has been largely overlooked, includes quantitative data on curlew abundance trends from 1875 to 1897 on Nantucket Island, Massachusetts. MacKay observed 650 curlews and his party bagged 87 during 231 hunting days logged during the flight period (21 August–2 October) over 22 hunting seasons. The last major flights were observed in 1881. Although he continued to hunt enthusiastically through the early 1890s, annual totals of curlews observed by MacKay declined significantly (rs, = 0.40, p < 0.05) from 1875 to 1897, as did annual bag totals (rs = -0.41, p < 0.05). Annual bag totals of American Golden Plovers (Pluvialis dominica),...

An approach for regional threat assessment under IUCN Red List criteria that is robust to uncertainty: The Fiordland bottlenose dolphins are critically endangered

Numerous globally abundant species are exposed to human impacts that threaten the viability of regional populations. Assessing and characterising the risks faced by these populations can have significant implications for biodiversity conservation, given the ecological importance of many such species. To address these risks, the IUCN is starting to conduct assessments of regional populations in addition to species-level assessments of conservation status. Here, we demonstrate a threat assessment process that is robust to uncertainty, applying the IUCN criteria to a regional population of bottlenose dolphins in Fiordland, New Zealand. We compiled available population-specific information to assess the population under the five Red List criteria. We estimated there were 205 Fiordland bottlenose dolphins (CV = 3.5%), using current estimates of abundance for two sub-populations and stochastic modelling of an earlier estimate for the third sub-population. Population trajectory and extinction risk were assessed using stochastic age-structured Leslie matrix population models. The majority of model runs met the criteria for classification as critically endangered (C1: 67.6% of runs) given the number of mature individuals (123; CV = 6.7%) and the predicted rate of population decline (average decline: 31.4% over one generation). The evidence of isolation of the population confirms this was an appropriate regional classification. This approach provided an assessment that was robust to uncertainty.

Rapid population declines of Himalayan Griffon Gyps himalayensis in Upper Mustang, Nepal

SummaryThe population collapse of resident Gyps vulture species in South Asia, caused by the use of a veterinary drug diclofenac, has highlighted an urgent need to monitor numbers of other vulture species in the region. This study assessed population trends of Himalayan Griffon Gyps himalayensis in the mountainous region of Upper Mustang, Nepal, which is an important breeding area for the species. Vultures were surveyed in 2002, 2004 and 2005 by recording the number of birds sighted along 188 km of transects, and observing numbers of birds at breeding colonies. The number of birds recorded per day and per kilometre of transect declined by 67% and 70% respectively over the period of study. The number of active nests declined by 84% from 2002 to 2005. The veterinary drug diclofenac was available in pharmacies in the Mustang region. Young Himalayan Griffons, which migrate to the lowland areas of Nepal and, in increasing numbers to India, are highly likely to be subject to diclofenac poisoning. If this rate of population decline occurs throughout the Himalayan region, the conservation status of the species will need to be urgently reassessed.

Pre-arranged funerals for self-fulfillment among elderly people : An analysis of the attitudes toward utilization of pre-arranged funerals to women belonging to a regional women’s organization

Purpose : This study aimed to investigate how local women think about utilizing pre-arranged funerals in Japan, and their relating factors.Methods : A questionnaire about to pre-arranged funerals were distributed to the members of regional women’s organizations in 6 Prefectures in Japan, that were characterized by 1) a high rate of aging, 2) a high rate of population decline, 3) small economic scale, and 4) small population size. Data were collected from 584 women, and they were analyzed with statistical package (spss ver. 17).Results : Spouses were mostly requested to take care of the womens’ wishes after death. More than half of the women wanted to utilize pre-arranged funerals. The period when women would like to utilize pre-arranged funerals was most commonly stated as the time when they thought such a funeral would be necessary. Multi logistic regression analysis also revealed that women who would like to utilize pre-arranged funerals were significantly associated with the following characteristics : women who requested palliative care from their brothers and/or sisters, women who had lost their spouse, and women who knew about end-of-life care.Conclusion : It was suggested that pre-arranged funerals have aspects of reducing funeral expenditure their spouse and those of self-fulfillment.

Elements of Population Dynamics of Bagworm (Lepidoptera: Psychidae) on Hedge Rows of White Pine

Spatiotemporal elements related to the population dynamics of bagworms, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae), on white pine, Pinus strobus (L.), were investigated by sampling populations of bagworms repeatedly at 12 sites within a 50-km radius in central Indiana. The number of live bagworms declined over time by up to 95% in some sites, and the rate of population decline increased with the initial density of larvae. A comparison of population density of bagworms in past generations with that of the current-year generation revealed that sites heavily infested with bagworms from previous years carried a high number of live larvae early but not late in the season. The positive relationship between densities of bagworms in past and current generations observed at five of 12 sites suggests that larvae commonly do not disperse when they emerge on a suitable host. However, there was considerable variation relative to this pattern, suggesting that dispersal is common as well. Pupation and emergence of adults occurred in late summer and early fall, with some level of phenological asynchrony observed at different sites. Dates corresponding to 50% pupation or adult emergence varied by up to 12 d at different sites. Males suffered higher mortality than females during the pupal stage. The positive correlation between the mortality level of female pupae and previous years' population density may be related to a buildup of populations of natural enemies in sites that were previously heavily infested with bagworms.

Sarcoptic mange in red deer from Spain: Improved surveillance or disease emergence?

Concern about emerging diseases has risen in recent years, and multihost situations have become increasingly relevant for wildlife management and conservation. We present data on Asturias, northern Spain, where 80 mangy red deer ( Cervus elaphus) have been found since the beginning of the epizootic in chamois ( Rupicapra pyrenaica parva) in 1993. We combine field and necropsy data with the results of a serosurvey using an in-house ELISA test to evaluate if deer mange due to Sarcoptes scabiei is an emerging disease in this area. The mean number of deer mange cases per year was 5, with a maximum of 16. No significant relationship was detected between monthly temperatures, rainfall or number of days with snow cover and the annual number of sarcoptic mange cases in red deer. Only 4 mangy red deer (5%) were detected outside the limits of scabietic chamois distribution during the same year, and all were less than 2500 m away from that limit. The longest distance reported between two consecutive mangy deer locations was 18 km. Mange cases were significantly more frequent in stags than in hinds and in adults than in juvenile deer. The time of the first mange detection in chamois in each sector, year with minimum number of chamois recorded, year with maximum chamois population decline rate and chamois density offered no significant correlation with red deer mange cases appearance moment and frequency. In the mange affected area, ELISA testing of 327 blood samples from hunter-harvested deer without obvious mange-compatible lesions revealed only 4 seropositive animals. All 83 sera from hunting preserves without clinical cases yielded negative ELISA results. According to these epidemiological data mange does not seem to threaten red deer populations in Asturias. However, continued monitoring of deer health and ELISA testing for sarcoptic mange is advisable.

Targeted management intervention reduces rate of population decline of Corn Buntings Emberiza calandra in eastern Scotland

Capsule Breeding populations were less likely to decline when farmland was subject to management intervention designed to benefit the species. Aims To determine whether targeted management intervention helps to halt or reverse the decline of Corn Buntings in eastern Scotland. Methods Counts of territorial male Corn Buntings in the breeding seasons of 2002 and 2004 were compared across 53 2-km squares. Nineteen of these were subject to management intervention designed to benefit Corn Buntings, effective from 2003. The other 34 had no such management. For a subset of 44 tetrads, counts in 2000 and 2002 were also compared between the two sets of tetrads. Results Between 2002 and 2004, Corn Bunting numbers showed no significant change in tetrads with targeted management intervention, but declined by 43% in tetrads with no intervention. By contrast, population changes did not differ significantly in these two groups of tetrads between 2000 and 2002, before management was implemented. Conclusion Targeted management intervention was associated with reduced short-term probability of Corn Bunting population decline on farms in eastern Scotland. Management interventions that are designed to provide habitats required by the species have the potential to halt, or perhaps reverse, the Corn Bunting decline in eastern Scotland.

Parasites as weapons of mouse destruction

Epidemiological models illustrate that parasites can drive fluctuations in host populations, but small-mammal ecologists have tended to reject parasitism as an important factor. In one of the few experimental tests of the impact of parasites on wildlife population dynamics, Pedersen and Greives reduced prevalence of intestinal nematodes in free-ranging populations of Peromyscus mice with and without access to supplemental food. In isolation, parasite removal and food addition reduced rates of population decline only modestly, but the two factors acted synergistically to strongly alleviate declines. It is tempting to disregard factors that, in isolation, have weak effects, but the results from Pedersen and Greives' multifactor experiment remind ecologists that complex factor interactions pervade real ecosystems.

Simulation model for contraceptive management of the Assateague Island feral horse population using individual-based data

The National Park Service (NPS) manages a culturally significant population of feral horses (Equus caballus) inhabiting the Maryland portion of Assateague Island, a barrier island in the eastern United States. Rapid growth of this population over the past few decades from 28 to 166 horses negatively impacts native species and ecological processes on the island. Since 1994, contraception via porcine zona pellucida vaccine has been used to control horse numbers, although herd reduction has been slower than initially expected, leading NPS to consider other management options. An individual-based stochastic simulation model was developed using the Vortex software program to examine the effects of different management strategies on the population. Data from the managed population were used to populate the model parameters. Model projections over the next 50 years using current management practices show an average rate of population decline of 13% per year, suggesting that the population will reach the management target of 80–100 horses in 5–8 years. The effectiveness of contraception to reduce the herd and maintain it at various target sizes of 20–100 horses was also assessed. The accumulation of inbreeding at each target population size was also modelled.

Population Modeling of Prairie Dog Contraception as a Management Tool

Recently, wildlife contraception became a reality with the registration of OvoControl for geese and pigeons. A data submission to the Environmental Protection Agency for the registration of GonaCon™ for white-tailed deer is forthcoming. The question that is now facing wildlife managers is if, and how, to implement contraception as part of an overall management plan. Population models offer a method of predicting the long-term efficacy of management actions without investing time and money in expensive field studies. Black-tailed prairie dogs were used as a target species for the purposes of these models. Four different management options were modeled for a 100-year period including no control, lethal control only, fertility control only, or a combination of lethal and fertility control. Yearly culling resulted in a more rapid rate of population decline than yearly contraception. Culled populations (50-90% culling) went extinct more quickly than populations contracepted at the same rate. Populations could be stabilized at their current size with 12.79% yearly culling or 33.25 % yearly contraception. Populations also remained relatively stable over 100 years when 50% of the population was culled initially, followed by 85.8% contraception once every 3 years. These models will help provide a scientific basis for further discussion on the usefulness of wildlife contraceptives, and will help highlight the areas that need further research.

Rapid population declines of Egyptian vulture (Neophron percnopterus) and red‐headed vulture (Sarcogyps calvus) in India

AbstractSince the early 1990s, large and rapid population declines of three species of vulture (Gyps spp.) endemic to south Asia have occurred on the Indian subcontinent and have led to these species being listed by IUCN as critically endangered. Evidence of rates of population decline, cause of death and toxicity is consistent with these declines being caused by poisoning of vultures through the ingestion of tissues from livestock treated with the anti‐inflammatory drug diclofenac. In this paper, analysis of repeated surveys in and near protected areas widely spread across India shows that populations of two other vulture species, Egyptian vulture Neophron percnopterus and red‐headed vulture Sarcogyps calvus, have also declined markedly and rapidly, but probably with a later onset than Gyps vultures in the same region. The declines continued at least up to 2003. It is recommended that these two species are considered for inclusion in the IUCN Red List and for urgent remedial conservation measures. Research is needed to determine whether or not the principal cause of these declines is diclofenac poisoning and to establish population trends in other scavenging birds in the Indian subcontinent.

Population Demography and Herbivory of Trillium Grandiflorum

Numerous pedicellate and sessile Trillium species are endemic to eastern North America, where white-tailed deer (Odocoileus virginianus) populations have been growing in recent decades. Deer feed on Trillium plants, and because they often consume all leaves and flowers, the photosynthetic capacity of browsed plants is greatly diminished. To determine if deer can influence Trillium population dynamics, we review two recent studies that applied matrix population models to understand how deer browsing affects Trillium grandijlorum. Research conducted in the Great Lakes region indicated Trillium populations in which 6-12% plants were browsed declined 3.6% per year. Simulations show that with additional browsing, the rate of population decline accelerates. Similar research conducted in the Appalachian plateau region by a different researcher yielded nearly identical results. We apply insights from these matrix population models to two additional conservation problems in Trillium: unsustainable collecting of wild plants and forest fragmentation. Because other Trillium in the eastern United States are similar morphologically and ecologically, our results from Trillium grandiflorum might be generalized to apply to other members of the genus.

In Trouble in Canada - The Northern Spotted Owl

Conservation and politics are inextricably linked for the Northern Spotted Owl which lives in economically valuable old-growth coniferous forests. Approximately 8% of the global range is located in Canada, with an estimated population of less than 30 pairs - all residing in the southwest mainland of British Columbia (BC). Historical inventory figures indicate the Canadian population has declined by approximately 46% since 1992, an average annual decline of 7.2%. Extirpation of the Northern Spotted Owl from Canada is likely imminent if the current rate of population decline continues. This species is extremely vulnerable to extirpation because of their small population size (<30 pairs), the need for large amounts of habitat, and low population densities. In BC, high quality habitat tends to be in forests >140 years old and moderate quality habitat occurs in forests 100-140 years old. Loss and fragmentation of habitat to harvesting of oldgrowth forests and degradation of habitat as a result of even-aged management of forests are widely believed to be the primary long term threats to the Northern Spotted Owl throughout the Pacific Northwest. Evidence suggests that management efforts to date have been unsuccessful at reversing the decline, and that more intensive efforts are required.

Measuring marine fish biodiversity: temporal changes in abundance, life history and demography

Patterns in marine fishes biodiversity can be assessed by quantifying temporal variation in rate of population change, abundance, life history and demography concomitant with long-term reductions in abundance. Based on data for 178 populations (62 species) from four north-temperate oceanic regions (Northeast Atlantic and Pacific, Northwest Atlantic, North mid-Atlantic), 81% of the populations in decline prior to 1992 experienced reductions in their rate of loss thereafter; species whose rate of population decline accelerated after 1992 were predominantly top predators such as Atlantic cod (Gadus morhua), sole (Solea solea) and pelagic sharks. Combining population data across regions and species, marine fishes have declined 35% since 1978 and are currently less than 70% of recorded maxima; demersal species are generally at historic lows, pelagic species are generally stable or increasing in abundance. Declines by demersal species have been associated with substantive increases in pelagic species, a pattern consistent with the hypothesis that increases in the latter may be largely attributable to reduced predation mortality. There is a need to determine the consequences to population growth effected by the reductions in age and size at maturity, and in mean age and size of spawners, concomitant with population decline. We conclude that reductions in the rate of population decline, in the absence of targets for population increase, will be insufficient to effect a recovery of marine fishes biodiversity, and that great care must be exercised when interpreting multi-species patterns in abundance. Of fundamental importance is the need to explain the geographical, species-specific and habitat biases that pervade patterns of marine fishes recovery and biodiversity.

Growth of female southern elephant seals Mirounga leonina at Macquarie Island

Body growth of 137 female southern elephant seals (Mirounga leonina) over 1 year of age was investigated at subantarctic Macquarie Island. An asymptotic straight line, snout–tail body length of 2.57±0.03 m was estimated to be attained at 9 years of age, using a three-parameter Gompertz equation. A significant increase of approximately 0.1 m (5%) in mean body length of females between 1 and 10 years of age was estimated to have occurred between the 1950–1960s and 1990s at Macquarie Island. This is consistent with a reduction in both the rate of population decline and the age of onset of sexual maturity. Age determination using dental cementum layers and the importance of standardised measurements in pinniped growth studies are discussed.

Diclofenac poisoning as a cause of vulture population declines across the Indian subcontinent

Summary Rapid population declines of the vultures Gyps bengalensis, Gyps indicus and Gyps tenuirostris have recently been observed in India and Pakistan, continuing at least up to 2003. Surveys indicate annual rates of decline of 22–50% for G. bengalensis and G. indicus during 2000–03. Previous studies in Pakistan have shown that the non‐steroidal anti‐inflammatory drug diclofenac causes renal failure and is lethal to G. bengalensis when it feeds on the carcass of a domestic animal that received a normal veterinary dose shortly before death. In Pakistan, diclofenac poisoning was found to be by far the most frequent cause of death. A simulation model of vulture demography, described in this paper, demonstrated that the observed rates of population decline could be caused by contamination with a lethal level of diclofenac in a small proportion (between 1 : 130 and 1 : 760) of ungulate carcasses available to vultures. Proportions of adult and subadult vultures found dead or dying in the wild that had signs of diclofenac poisoning were similar to the proportions of deaths expected from the model if the observed population decline was due entirely to diclofenac poisoning. The proportion of the excess mortality required to cause the observed population declines that could be attributable to diclofenac was estimated to be between 71% and 100%, depending on model assumptions. However, across all or most of the plausible range of assumed values for adult survival, the upper 95% confidence limit for the proportion of excess mortality due to diclofenac was 100%. Hence, available data are consistent with diclofenac poisoning being at least the major cause, and possibly the only cause, of rapid population declines of Gyps vultures across the Indian subcontinent. Synthesis and applications. We recommend that urgent action is taken in the range states of the three currently threatened vulture species to prevent the exposure of vultures to livestock carcasses contaminated with diclofenac. Research is also needed to identify alternative drugs that are effective in livestock and safe for vultures. Efforts should also be made to raise awareness, among veterinarians, pharmacists, livestock owners and the general public, of the problem of diclofenac contamination and the availability of safe alternatives. Captive holding and breeding of vultures until diclofenac is controlled is recommended as a precaution to ensure the long‐term survival of the threatened species and to provide a stock of birds for future reintroduction programmes.

Genetic Effects of a Persistent Bottleneck on a Natural Population of Ornate Box Turtles (Terrapene ornata)

Human activities in the past few hundred years have caused enormous impacts on many ecosystems, greatly accelerating the rate of population decline and extinction. In addition to habitat alteration and destruction, the loss of genetic diversity due to reduced population size has become a major conservation issue for many imperiled species. However, the genetic effects of persistent population bottlenecks can be very different for long-lived and short-lived species when considering the time scale of centuries. To investigate the genetic effects of persistent population bottlenecks on long-lived species, we use microsatellite markers to assess the level of genetic diversity of a small ornate box turtle population that has experienced a persistent bottleneck in the past century, and compare it to a large relatively undisturbed population. The genetic signature of a recent bottleneck is detected by examining the deviation from mutation-drift equilibrium in the small population, but the bottleneck had little effect on its level of genetic diversity. Computer simulations combined with information on population structure suggest that an effective population size of 300, which results in a census population size of 700, would be required for the small population to maintain 90% of the average number of alleles per locus in the next 200 years. The life history of long-lived species could mask the accelerated rate of genetic drift, making population recovery a relatively slow process. Statistical analysis of genetic data and empirical-based computer simulations can be important tools to facilitate conservation planning.

Spatial stability of Avena sterilis ssp. ludoviciana populations under annual applications of low rates of imazamethabenz

SummaryLong‐term experiments were conducted in two winter barley fields in central Spain to determine the spatial stability of Avena sterilis ssp. ludoviciana populations under annual applications of low rates of imazamethabenz herbicide. Weed density was sampled every year (over 5 years in the first field and over 3 years in the second) on the same grid locations prior to herbicide application. Although weed patches were stable in their location, weed density decreased in most of the years. In the first field, the populations decreased exponentially over the 5‐year period. The rates of population decline were dependent on the initial density of the population, being higher for the central core of the patches and lower for the low‐density areas. Under the conditions present in this experiment, it was possible to reduce heavy weed patches (up to 1200 seedlings m−2) down to relatively safe levels (18 seedlings m−2) in a period of 3 years using a density‐specific control programme, applying low rates of herbicides when weed densities were below a given level (1000 seedlings m−2). However, under adverse environmental conditions, half rates of the herbicide failed to control the weed populations adequately. The stability of the location of patches of A. sterilis ssp. ludoviciana suggest that weed seedling distributions mapped in one year are good predictors of future seedling distributions. However, the actual densities established each year will depend on the control level achieved the previous year and the climatic conditions present during the establishment period.

Effects of compost addition and simulated solarisation on the fate of Ralstonia solanacearum biovar 2 and indigenous bacteria in soil

Abstract The effects of compost addition and simulated solarisation of soil on the survival of Ralstonia solanacearum biovar 2 strain 1609, as well as on the structure of indigenous soil bacterial communities, were analysed. In addition, effects on the invasion of susceptible test plants by strain 1609 were assessed. In untreated soil in microcosms and the field, strain 1609 showed slow progressive declines, from 10(6)-10(7) to roughly 10(4)-10(5) CFU per g dry soil in around 60 days. When these soils were used in suppressiveness tests, a majority of plants developed symptoms of wilting and revealed the presence of the pathogen in their lower stem parts, as evidenced by immunofluorescence colony staining (IFC) and polymerase chain reaction (PCR). Solarisation of unamended soil did not drastically affect R. solanacearum survival or plant invasiveness. However, the addition of household compost resulted in enhanced R. solanacearum population decline rates, as well as reduced numbers of diseased plants in suppressiveness tests. Combined solarisation and compost addition yielded differential results between microcosms and the field. Some healthy-looking plants, primarily from soils treated with compost, revealed the latent presence of strain 1609 in the lower stem parts. The eubacterial and beta-subgroup proteobacterial communities in the differentially treated soil microcosms were rather stable, as evidenced by analysis of PCR-denaturing gradient gel electrophoresis (DGGE) generated molecular profiles. However, compost amendment clearly induced changes in these communities, which were detectable until the end of the experiment; two major bands, affiliated with Variovorax paradoxus and Aquaspirillum psychrophylum, were associated with the compost amendment. The decrease in abundance of R. solanacearum in the compost-amended soils was confirmed by the DGGE profiles.