Epidemiology and conservation implications of Trichomonas gallinae infection in the endangered Mauritian pink pigeon

Despite increasing recognition of the role of exotic pathogens in species decline, comprehensive studies of wildlife disease epidemiology in threatened species are rare. We investigated the epidemiology of the protozoan parasite Trichomonas gallinae, which causes the avian disease trichomonosis, in the five wild subpopulations of the endangered pink pigeon Columba mayeri in Mauritius. An average of 89% of the entire population was screened for T. gallinae infection every 2 months between September 2002 and April 2004. A total of 426 individual pink pigeons (all >3 months of age) was screened, and 359 (84.3%) of these tested positive for T. gallinae at least once. Average prevalence of T. gallinae infection across all subpopulations and sampling periods was 50.3% but ranged from 19.6% to 82.4%. Trichomonas gallinae infection was significantly different among subpopulations and prevalence gradually decreased over the entire screening period. Infection prevalence also increased with host age. Observed pathogenicity of T. gallinae was low; active trichomonosis signs were recorded in ca. 1.9% of birds which tested positive. However, birds which persistently tested positive for T. gallinae (33.5% of birds screened) were at least 10% less likely to survive 2 yrs post-screening than birds which tested negative at least once in three consecutive periods; a finding which should be considered by wildlife disease investigators if no pathogenic effects are apparent from the results of studies based on a single screening episode. We conclude that T. gallinae is an additional population limiting factor for pink pigeons and our study highlights the importance of screening other endangered columbids for this pathogen.     

Distribution and stand characteristics of relict populations of Mexican beech (Fagus grandifolia var. mexicana)

Fagus grandifolia var. mexicana (Mexican beech) is limited to about 10 populations (2-35 ha) in the Sierra Madre Oriental, Mexico. The objectives were to assess the current status and distribution of beech by surveying five sites. Species richness varied between three to 27 tree species in the canopy, and from nine to 29 species in the understorey. Basal area of trees?5 cm dbh varied between 27.87 and 70.98 m² ha⁻¹, and density from 370 to 1290 individual ha⁻¹. Beech represented 22-99.6% of total basal area, and 6.8-83.3% of total density. Beech dominance varied from monodominant to codominance with Carpinus caroliniana, Quercus spp., Liquidambar styraciflua, Magnolia schiedeana, and Podocarpus spp. Beech total population size ranged from 180 to 6300 trees with a total of less than 1300 individuals in four sites. Anthropogenic disturbance remains a major threat to these forests. It is uncertain whether Mexican beech will be able to survive without conservation efforts.     

Waiting reveals waning weight: Monitoring over 54 years shows a decline in body condition of a long-lived reptile (tuatara, Sphenodon punctatus)

Knowledge gained from monitoring has been the basis for many critical decisions in threatened and endangered species and ecosystem management. Long-term monitoring has been recognized as a necessity for elucidating population trends and community interactions, particularly for long-lived species or ecosystems with slow rates of change. We examine seasonal and annual cycles of morphological changes in a threatened, long-lived, insular reptile, the tuatara (Sphenodon punctatus), on Stephens Island, New Zealand. We used body condition indices as a surrogate measure of fitness, and examined seasonal fluctuations, using data from an intensive mark-recapture study, and long-term trends using a dataset that spans 54 years. In spite of seasonal and annual fluctuations, body condition of tuatara has declined significantly between 1949 and 2003; the decline was only evident after >22 years of monitoring. We hypothesize that increasing numbers of tuatara have resulted in a density-dependent population response driven by past habitat modification on Stephens Island. We emphasize the need for long-term monitoring and suggest that potentially costly management decisions, particularly for long-lived species or ecosystems with slow rates of change, should not be based solely on short-term monitoring.     

Patterns of mortality in a cold-climate population of garter snakes (Thamnophis sirtalis parietalis)

The causes, magnitude and phenotypic determinants of mortality are central features of population demography. Although critical to effective conservation planning, these attributes remain poorly understood for most wild vertebrates. Exceptionally dense aggregations of garter snakes (Thamnophis sirtalis parietalis) in and around communal overwintering dens in central Manitoba provide an exceptional opportunity to enumerate these factors. Over the course of long-term field studies we obtained data on mortality of snakes in autumn as they migrated back from their summer ranges, and in winter during and after their entry into the underground dens. Some mortality sources were affected by a snake's phenotype: for example, snakes killed by motor vehicles were smaller, on average, than surviving snakes. However, two major episodes of mortality at the dens themselves (freezing during midwinter due to atypically light snow cover; and drowning due to flooding after heavy rains late in autumn) were essentially random with respect to phenotype. Mark-recapture estimates suggest that the winterkill event eliminated >60,000 snakes, comprising almost the entire populations of the three largest dens. Although such events are cryptic because the bodies of frozen animals remain underground, they are of much greater magnitude than overt mortality sources for active snakes (roadkills, predation, etc.). Thus, relatively minor habitat manipulations around the dens may contribute more to conservation of these populations than would extensive efforts to protect active snakes during their spring and autumn migrations.     

Translocations of eight species of burrow-nesting seabirds (genera Pterodroma, Pelecanoides, Pachyptila and Puffinus: Family Procellariidae)

Development of seabird translocation techniques is required to meet species recovery objectives, to improve conservation status, and to restore ecological processes. During 1997-2008 we undertook translocation trials on eight petrel species of four genera within the New Zealand region: common diving petrel (Pelecanoides urinatrix), fairy prion (Pachyptila turtur), grey-faced petrel (Pterodroma macroptera gouldi), Pycroft’s petrel (Pterodroma pycrofti), Chatham petrel (Pterodroma axillaris), Chatham Island taiko (Magenta petrel; Pterodroma magentae), fluttering shearwater (Puffinus gavia), and Hutton’s shearwater (Puffinus huttoni). A total of 1791 chicks within 5 weeks of fledging were moved up to 240 km, placed in artificial burrows and hand-fed until they fledged. Of these, 1546 fledged, and so far at least 68 have returned as adults to the translocation sites. Most birds were crop-fed a puree based on tinned sardines and fresh water. This diet worked well for all species regardless of their typical natural diet (planktonic crustaceans, squid, or fish) with all species fledging above or close to mean natural fledging weights.     

Two-sex population projection of the endemic and dioecious rainforest shrub, Gardenia actinocarpa (Rubiaceae)

Gardenia actinocarpa (Rubiaceae)—an endemic and dioecious shrub-small tree of the lowland rainforest of Cape Tribulation, NE Australia—is evaluated for its long-term population persistence using five-year demographic data from three permanent plots of the species. Two-sex, size-specific Lefkovitch matrices were constructed to evaluate the species’ vital rates and extinction thresholds. One site indicated a sign of significant population growth (annual λ=1.056), while the remaining two gave λs close to unity (λ=1.0102 and 1.007). Overall, λ was greater than 1 (λ=1.0281) indicating that G. actinocarpa will increase in population size with time, though male plants were projected to grow faster in number than female plants. Elasticity analyses indicated that the largest size class (>22 cm diameter) made the greatest contribution to population growth (28%), especially the male plants (23%). Also λ was equally sensitive to survival/stasis (45%) and growth (44%) and least sensitive to fecundity (11%). Stochastic simulations gave 0.505 probability of quasi-extinction to 10% of its initial size in 100 years of population growth projection- suggesting that the endemic G. actinocarpa, despite a positive rate of population increase, is indeed threatened. Sensitivity analyses and numerical simulations showed that to maintain population persistence of G. actinocarpa, efforts should concentrate, following cost-benefit analyses, on increasing seed production coupled with enhancing establishment of individuals in the seedling, juvenile and vegetative phases.     

High rates of forest clearance and fragmentation pre- and post-National Park establishment: The case of a Jamaican montane rainforest

The principal defense of tropical forests has been to designate them as protected areas, but few of these protected areas have been studied to determine their effectiveness at preventing forest clearance within their boundaries. We used remote sensing techniques to quantify three fundamental forest cover change processes: forest clearance, re-growth and fragmentation over a 19-year time period, in a National Park of Jamaica. Results show that forest clearance occurred at similar high levels prior and subsequent to the establishment of the area as a National Park in 1993: 1.50% yr⁻¹ (1983–1992) and 1.42% yr⁻¹ (1992–2002), respectively. Fragmentation continued post-establishment, and manifested itself in an increasing number of smaller more vulnerable fragments; the number of fragments increased by 60%, and the mean fragment size decreased by 40%. Core areas decreased with ensuing increases in edge lengths, and fragments became more isolated from one another. After designation as a National Park however, increased forest re-growth occurred, resulting in a 63% decline in the net deforestation rate from 0.80% yr⁻¹ (1983–1992) to 0.26% yr⁻¹ (1992–2002). Image classifications gave accuracies of 90–97% (Kappa 0.80–0.93). Although the decrease in net deforestation may indicate some level of success of this National Park, forest clearance and fragmentation, leading to species shifts and biodiversity loss were still present at pre-National Park levels. We then examined the preponderance of successful protected areas, and found that success may be an artifact of the most widely used method of assessment, which compares deforestation rates inside versus outside protected areas.     

Estimating population size in the subdesert mesite (Monias benschi): new methods and implications for conservation

The subdesert mesite, a terrestrial non-passerine bird endemic to the Mikea Forest of southwest Madagascar, is currently classified as globally threatened (category: Vulnerable). However, accurate assessment of threat in accordance with the IUCN Red List criteria (A, B and C) requires data on effective population size, area of habitat occupied and rate of decline, none of which is available for this species. Here we present the first empirical estimates of its population size using five complementary methods, three incorporating data on territory size and two using data gathered during call-playback surveys conducted throughout its entire global range. Estimates vary from 98,000 to 152,000 individuals, with the most reliable possibly being that generated by distance sampling (115,000). This figure is more than an order of magnitude greater than the only published estimate of <10,000 individuals. By analysing data on forest cover change, we estimate the population of the subdesert mesite to have declined by, at most, 10% in three generations. Although the rate of deforestation in 1994-1999 is double that calculated for 1962-1994, it is deemed unlikely that the population will decline by 20% over the next three generations. As such the species fails to meet criterion A. Although the subdesert mesite's range and area of occupancy are small, they are not fragmented and do not comprise fewer than 10 locations. Consequently, this species does not meet criterion B. Further, the species fails to meet criterion C, for which a maximum of 10,000 mature adults is required. According to IUCN (2000 Red List of Threatened Species) this species should therefore be downlisted in status. We discuss why it still warrants conservation attention and suggest the need for modifications to the criteria thresholds in relation to basic information about the ecology and taxonomic distinctness of species.     

Exposure to ecotourism reduces survival and affects stress response in hoatzin chicks (Opisthocomus hoazin)

Ecotourism helps to protect many habitats, but may also have negative impacts on wildlife. We investigated effects of ecotourists on reproductive success of hoatzins (Opisthocomus hoazin) and on hormonal status of their chicks in Amazonian rainforest lakes by comparing birds from undisturbed and from tourist-exposed nests. Hatching success was similar in both groups but chick survival was much lower at tourist-exposed nests than at undisturbed nests. This effect was due to an increased mortality of juveniles prior to fledging whereas small nestlings seemed largely unaffected. Juveniles, but not nestlings, living at tourist-exposed sites had a lower body mass and showed a stronger hormonal response to experimental stress compared to individuals at undisturbed sites. These data suggest that juvenile hoatzins were susceptible to tourist-induced stress which in turn may be responsible for the lower survival. In contrast, adult hoatzins that were incubating had apparently habituated to tourist presence because their flush distances at tourist-exposed nests were 50% lower than at undisturbed sites. Our findings demonstrate that individuals in different life stages show different susceptibilities to tourism. We suggest that even just watching animals during breeding can threaten their survival, but a proper scientific management of off-limit zones and area-specific guidelines for wildlife observation could reduce harmful effects.     

Illegal killing slows population recovery of a re-introduced raptor of high conservation concern - The red kite Milvus milvus

The re-introduction of extirpated species is a valuable conservation tool. Red kites Milvus milvus are declining over much of their European range and have been re-introduced to England and Scotland, following their extinction due to widespread human persecution during the 19th century. Considerable regional variation in population growth exists. This study aims to identify the proximate demographic and ultimate environmental constraints on red kites in north Scotland, a region with low population growth. Productivity in north Scotland was high compared to other Scottish and Welsh populations and equal to English populations with high population growth rates. In north Scotland, annual survival of wild-fledged birds was low for first-year birds compared to other Scottish populations and second-year survival declined over time. In north Scotland, 40% of 103 red kites found dead were killed illegally, mainly by direct poisoning. In the absence of illegal killing, we estimate that annual survival rates in wild red kites might increase from 0.37 to 0.54, 0.72 to 0.78 and 0.87 to 0.92 for first, second-year and adult birds respectively. Demographic rates from this study produce population trends that recapitulate observed trends for the north Scotland population (leading to a population of c40 pairs by 2006). Models in which the additive illegal killing mortality is excluded, predict a population trajectory and size (c300 pairs by 2006) very similar to that found in the Chilterns, a rapidly growing population (320 pairs in 2006) in south-east England re-introduced at the same time, but where rates of illegal killing are much lower. We conclude that illegal killing of red kites is the cause of poor population growth in north Scotland and the key challenge facing government is to find a way to eliminate this killing.     

Current status and conservation of white-headed langur (Trachypithecus leucocephalus) in China

The white-headed langur is classed as a category I species under the Wild Animal Protection Law in China. It is distributed only in Karst hills in four counties (Longzhou, Ningming, Chongzuo and Fusui), in the southern Guangxi province of China. The Mingjiang River and the Zuojiang River form its southern, western and northern boundaries, and the Shiwandashan Mountains restrict its range in the east. Population surveys conducted in the 1980s showed that there were a total of 630 individuals in Guangxi, including 244 in Longzhou and Ningming counties, 117 in six fragments of Chongzuo County and 272 in nine patches of Fusui County. Surveys conducted by our group and Guangxi Forestry Bureau indicated that a total of 580-620 white-headed langurs still live in the above four counties, including 210-240 in Longzhou and Ningming, 90-100 in Chongzuo and 250 in Fusui. According to our statistics, only about 200 km² of habitat remains within the current range of the white-headed langur and this is separated as a total of 16 patches in 13 townships. Shangjin and Xiangshui in Longzhou county and Tingliang and Tuolu in Ningming, form the largest patch of the range, with total area of 68 km², while in Chongzuo and Fusui County, the habitat is heavily fragmented with six patches of 43.5 km² in Chongzuo and nine patches of 88 km² in Fusui. At present, the white-headed langur is still suffering from heavy habitat deterioration and human disturbance such as cultivation, tree-cutting for firewood, and poachings even though the government has made many efforts to protect this endangered species, such as putting it as a category I species for protection and designating the nature reserve and stations.     

Design and evaluation of a translocation strategy for the fringed darter (Etheostoma crossopterum) in Illinois

The fringed darter (Etheostoma crossopterum) was introduced into two streams where neither the fringed darter nor any other species of the same subgenus occur but that otherwise have suitable habitat. Darters were collected from two streams in the Cache River basin, and a combination of darters from each source stream were moved to the receiving streams, which also were in the headwaters of the Cache River basin (20 males and 40 females to each). Darters were moved in late March 2001 at the beginning of their reproductive season, which continues for approximately 2 months. Fringed darter nests were present within 3 days at both introduction sites and nests were found thereafter until late May at which time searching for nests was terminated. Twenty-five nests were found in 2001 compared with 168 nests in 2002. A total of 8714 eggs were counted in 22 nests during 2001 with a mean of 413 eggs per nest (n=19 nests). In September 2001 and 2002, surveys for juveniles and adults indicated successful recruitment in both streams. Mean size of juvenile darters differed significantly between the two introduction sites in 2001. The design of this study allowed for a rapid, initial assessment of the translocations, aspects of which appeared successful. Moving fishes at the beginning of their reproductive season could increase the chance of successful reproduction and eventual establishment. The protocol for translocation of fringed darters might be applicable to other similar and endangered darters such as Barrens (Etheostoma forbesi), relict (E. chienense), and duskytail darters (E. percnurum). Sampling was conducted in other areas of the Cache River basin in search of additional populations of fringed darters. An updated account is given of the distribution of the fringed darter in Illinois.     

Population structure and movements of a threatened butterfly (Lopinga achine) in a fragmented landscape in Sweden

The red-listed butterfly Lopinga achine was studied by mark-recapture methods in southern Sweden for three seasons. We examined movement within and between populations and egg production in relation to age. The majority of the movements were small with mean movements between recaptures of 45-54 m for males and 94-116 m for females. There were few movements between sites, 20 of 996 recaptured males moved and 36 of 391 recaptured females, even though the distance to other sites was in many cases <100 m. The distance moved and the number of females moving between sites increased with increasing age. On average, a female that moves does so after laying two-thirds of its eggs in its natal site. It is therefore important to take account of the proportion of reproductive effort involved in dispersal when estimating colonisation ability. The males did not move more with increasing age. Female behaviour can be seen as a “spread-the-risk” strategy, an adaptation to the successional habitat of L. achine, whose natal site sooner or later will deteriorate. Butterflies like L. achine living in successional habitats may exhibit mobility that is intermediate between butterflies living in ephemeral habitats (very mobile) and in long-lived habitats (sedentary).     

Conserving marginal populations of the food plant (Impatiens noli-tangere) of an endangered moth (Eustroma reticulatum) in a changing climate

Impatiens noli-tangere is scarce in the UK and probably only native to the Lake District and Wales. It is the sole food plant for the endangered moth Eustroma reticulatum. Significant annual fluctuations in the size of I. noli-tangere populations endanger the continued presence of E. reticulatum in the UK. In this study, variation in population size was monitored across native populations of I. noli-tangere in the English Lake District and Wales. In 1998, there was a crash in the population size of all metapopulations in the Lake District but not of those found in Wales. A molecular survey of the genetic affinities of samples in 1999 from both regions and a reference population from Switzerland was performed using AFLP and ISSR analyses. The consensus UPGMA dendrogram and a PCO scatter plot revealed clear differentiation between the populations of I. noli-tangere in Wales and those in the Lake District. Most of the genetic variation in the UK (H_T=0.064) was partitioned between (G_ST=0.455) rather than within (H_S=0.034) regions, inferring little gene flow occurs between regions. There was similar bias towards differentiation between metapopulations in Wales, again consistent with low levels of interpopulation gene flow. This contrasts with far lower levels of differentiation in the Lake District which suggests modest rates of gene flow may occur between populations. It is concluded that in the event of local extinction of sites or populations, reintroductions should be restricted to samples collected from the same region. We then surveyed climatic variables to identify those most likely to cause local extinctions. Climatic correlates of population size were sought from two Lake District metapopulations situated close to a meteorological station. A combination of three climatic variables common to both sites explained 81-84% of the variation in plant number between 1990 and 2001. Projected trends for these climatic variables were used in a Monte Carlo simulation which suggested an increased risk of I. noli-tangere population crashes by 2050 at Coniston Water, but not at Derwentwater. Implications of these findings for practical conservation strategies are explored.     

Conservation status and limiting factors in the endangered population of Egyptian vulture (Neophron percnopterus) in the Canary Islands

Egyptian vulture populations have decreased sharply in the Western Palearctic; island populations are almost extinct in the Mediterranean and the Macaronesian regions. In the Canary archipelago, the species only survives in the islands of Fuerteventura and Lanzarote. During 1998-2001 we examined population parameters and evaluated some potential limiting factors for this isolated and sedentary population. The total population (breeding and non-breeding birds) was monitored annually. In addition, 26 fledglings and 33 immatures (<6 years old) and adult birds were captured for individual marking with plastic rings. Twenty-three/twenty-four occupied territories were located in the island and the total population estimated at around 130 birds. Breeding success was lower than recorded elsewhere in the species' distribution area: only 0.43 fledglings/pair/year were produced. Adult (>6 years old birds) and immature annual survival rates were similar, around 90%. Adult survival was lower than expected as territorial birds seem more susceptible to poisoning. Immature survival could be favoured by the existence of regular feeding places. Casualties from power lines was the main cause of mortality (12 cases during the study period). Blood sampling revealed high frequencies of lead poisoning: 13.5 and 2.7% of individuals showed sub-clinical and clinical intoxication levels, respectively, probably caused by the ingestion of lead shot. Priority conservation measures should be directed to reduce electrocution risks, illegal poisoning, and lead contamination. Population reinforcement with birds coming from other populations is not recommended as previous information reveals morphological and genetic differentiation of Canarian Egyptian vultures compared with continental populations.     

Population viability of the narrow endemic Helianthemum juliae (CISTACEAE) in relation to climate variability

Narrow endemic plants are highly vulnerable to extinction as a result of human disturbance and climate change. We investigated the factors affecting the population viability of Helianthemum juliae, a perennial plant endemic to the Teide National Park on Tenerife, Canary Islands. One population was demographically monitored from 1992 to 2001 and analysed using matrix projection models to determine finite rates of increase and critical stages in the life cycle. Lambda values varied between 0.697 and 1.740, and were highly positively correlated with annual precipitation, but not with temperature. Survival of adults had the highest elasticity, and summed elasticities of the growth and fecundity transitions correlated positively with lambda and precipitation. Most of the mortality in the population seemed drought-related, and no other threats were identified. Deterministic simulations showed population increase, but introducing environmental stochasticity by modelling variation in precipitation from existing data of the past 85 years revealed high extinction probabilities (0.74-0.83 in the next 100 years). This plant is likely to be at risk under scenarios of global warming. Our simulations suggest that augmenting the population would only delay extinction. A more viable option for long-term conservation seems to be the introduction of populations at more humid locations within the Teide caldera.     

Survival of Marbled Teal (Marmaronetta angustirostris) released back into the wild

Reintroduction or re-enforcement programmes are major tools in species conservation, but there is a need for more studies that assess the influence of different husbandry and release methods on the survival of released animals. We investigated the survival of globally threatened Marbled Teal (Marmaronetta angustirostris) taken into captivity as ducklings when they became trapped in an irrigation channel, then released again after fledging. We used wing tags and mark-recapture models to estimate the survival of released teal. Ducklings rescued in 1996 (n = 53) were released soon after fledging in September and their survival was modelled for seven months until April 1997. Their apparent monthly survival rate (lower than true survival owing to loss of wing tags) was 0.85 ± 0.12 (±s.e.). Ducklings rescued in 1997 (n = 44) were released together in February 1998 over five months after fledging, and their survival was modelled for six months from February until August. Their apparent monthly survival rate was 0.54 ± 0.06. Ducklings rescued in 1998 (n = 159) were released in August-September soon after fledging and their survival was modelled for 10 months from August until June. Their apparent monthly survival rate was 0.83 ± 0.07. Monthly survival was significantly higher for the 1996 and 1998 cohort, suggesting that retaining birds in captivity after fledging had a negative impact on post-release survival. When birds were released in February, a lower proportion survived until the breeding season three months later than when they were released five months earlier in September.     

Relationship between population size and genetic diversity in endangered populations of the European bullhead (Cottus gobio): implications for conservation

This study investigated the relationship between the current size of endangered bullhead (Cottus gobio) populations and microsatellite genetic variability. Additionally, the microsatellite data were used to evaluate whether a genetic test for population bottlenecks was able to provide evidence of recent severe population declines. Finally, our results were used to develop conservation priorities and measures. Population size appears to be a crucial parameter in determining the amount of genetic diversity that can be preserved in bullheads, since a significant positive correlation was observed between both variables. Furthermore, in some populations we were able to detect genetic signatures of the documented decline in population size. We suggest that the most immediate goal for bullhead conservation should be to increase the size and the range of the populations, and in doing so minimise or even reverse further genetic erosion. Potential management actions like habitat quality improvement, reduction of river fragmentation and supplementation programmes (translocation, supportive breeding) are discussed.     

The re-expansion and improving status of the silver-spotted skipper butterfly (Hesperia comma) in Britain: a metapopulation success story

Many specialist species are declining as a result of habitat loss and fragmentation, such that conservation actions typically aim to stem rates of decline rather than bring about genuine recovery. Here, we document the recovery of a species from former population refuges. An extensive survey of the entire British range of Hesperia comma, conducted in 2000, recorded over three times the number of tetrads (2 km × 2 km grid squares) occupied in 1982. This was accompanied by a fourfold increase in the number of populations and a 10-fold increase in the habitat area occupied. The improving status of H. comma is the product of good habitat management, recovering rabbit populations and climate warming, which have improved the quality, and increased the availability, of suitable habitat. This has enabled remnant metapopulations to expand, via distance-dependent colonisation, through large networks of habitat. Metapopulation recovery in H. comma demonstrates that landscape-scale conservation can be successful.