Importance of getting the numbers right: quantifying the rapid and substantial decline of an abundant marsupial, Bettongia penicillata

2013 ◽  
Vol 40 (3) ◽  
pp. 169 ◽  
Author(s):  
A. F. Wayne ◽  
M. A. Maxwell ◽  
C. G. Ward ◽  
C. V. Vellios ◽  
B. G. Ward ◽  
...  
Keyword(s):  
Population Size ◽  
Population Change ◽  
Conservation Status ◽  
Nest Density ◽  
Population Declines ◽  
Bettongia Penicillata ◽  
Epbc Act ◽  
Substantial Decline ◽  
Endangered Status ◽  
Capture Rates

Context A reliable measure of population size is fundamental to ecology and conservation but is often difficult to obtain. The woylie, Bettongia penicillata, provides an example where ‘getting the numbers right’ has important implications in verifying and quantifying the recent unexpected, rapid and substantial declines across much of its range. Initial estimates prompted a conservation-status upgrade for the species to Endangered by the Australian Government. The present paper constitutes the foundational paper addressing the first steps of a decline diagnosis framework intended to identify the causes of the recent declines. Aims To verify whether the declines in woylie trap-capture rates are representative of population change; better quantify the size of the largest woylie populations; and review what is understood about the ecology of the woylie and identify key knowledge gaps that may be relevant to identifying the causes of the recent declines. Methods Monitoring data from live-cage trapping (transects and grids), sandpads, woylie diggings and nest-density surveys and spotlighting were collated. Population measures derived from trapping data included capture rates, number of individuals, abundance estimates based on capture–mark–recapture modelling and density using spatially explicit capture–recapture models (SECR). Key results The declines in woylie trap-capture rates were verified as real population declines and corresponded closely with other measures of abundance derived from the same trapping data as well as with independent measures. A 95% decline occurred in the largest extant woylie populations (in the Upper Warren region, Western Australia) between 2002 and 2008. At a species level, woylies declined ~90% (1999–2006), from a peak of ~200 000 individuals in 1999. Conclusions An accurate formal conservation status is an important factor in promoting the conservation of a species. It is recommended that the woylie be considered for Critically Endangered status under the Australian EPBC Act. Implications Adequate and effective monitoring of species is critical to detecting and quantifying population changes in a timely manner. Having an accurate measure of population size can have a significant impact on the effectiveness of conservation and management efforts.

scholarly journals Assessing conservation status of resident and migrant birds on Hispaniola with constant-effort mist-netting

2015 ◽  
Author(s):  
John D Lloyd ◽  
Chris C Rimmer ◽  
Kent P McFarland
Keyword(s):  
Population Change ◽  
Conservation Status ◽  
Capture Rate ◽  
Temporal Trends ◽  
Bird Species ◽  
Quantitative Information ◽  
Neotropical Migrant ◽  
Migrant Birds ◽  
Conservation Assessments ◽  
Capture Rates

We analyzed temporal trends in mist-net capture rates of resident (n = 8) and overwintering Nearctic-Neotropical migrant (n = 3) bird species at two sites in montane broadleaf forest of the Sierra de Bahoruco, Dominican Republic, with the goal of providing quantitative information on population trends that could inform conservation assessments. We conducted sampling at least once annually during the winter months of January – March from 1997 – 2010. We found evidence of steep declines in capture rates for three resident species, including one species endemic to Hispaniola. Capture rate of Rufous-throated Solitaire (Myadestes genibarbis) declined by 3.9% per year (95% CL = 0%, 7.3%), Green-tailed Ground-Tanager (Microlegia palustris) by 6.8% (95% CL = 3.9%, 8.8%), and Greater Antillean Bullfinch (Loxigilla violacea) by 4.9% (95% CL = 0.9%, 9.2%). Two rare and threatened endemics, Hispaniolan Highland-Tanager (Xenolegia montana) and Western Chat-Tanager (Calyptophilus tertius), showed statistically significant declines, but we have low confidence in these findings because trends were driven by exceptionally high capture rates in 1997 and varied between sites. Analyses that excluded data from 1997 revealed no trend in capture rate over the course of the study. We found no evidence of temporal trends in capture rates for any other residents or Nearctic-Neotropical migrants. We do not know the causes of the observed declines, nor can we conclude that these declines are not a purely local phenomenon. However, our findings, along with other recent reports of declines in these same species, suggest that a closer examination of their conservation status is warranted. Given the difficulty in obtaining spatially extensive, long-term estimates of population change for Hispaniolan birds, we suggest focusing on other metrics of vulnerability that are more easily quantified yet remain poorly described, such as extent of occurrence.

scholarly journals Assessing conservation status of resident and migrant birds on Hispaniola with mist-netting

PeerJ ◽  
2016 ◽  
Vol 3 ◽  
pp. e1541 ◽  
Author(s):  
John D. Lloyd ◽  
Christopher C. Rimmer ◽  
Kent P. McFarland
Keyword(s):  
Population Change ◽  
Conservation Status ◽  
Capture Rate ◽  
Temporal Trends ◽  
Bird Species ◽  
Quantitative Information ◽  
Neotropical Migrant ◽  
Migrant Birds ◽  
Conservation Assessments ◽  
Capture Rates

We analyzed temporal trends in mist-net capture rates of resident (n= 8) and overwintering Nearctic-Neotropical migrant (n= 3) bird species at two sites in montane broadleaf forest of the Sierra de Bahoruco, Dominican Republic, with the goal of providing quantitative information on population trends that could inform conservation assessments. We conducted sampling at least once annually during the winter months of January–March from 1997 to 2010. We found evidence of declines in capture rates for three resident species, including one species endemic to Hispaniola. Capture rate of Rufous-throated Solitaire (Myadestes genibarbis) declined by 3.9% per year (95% CL = 0%, 7.3%), Green-tailed Ground-Tanager (Microligea palustris) by 6.8% (95% CL = 3.9%, 8.8%), and Greater Antillean Bullfinch (Loxigilla violacea) by 4.9% (95% CL = 0.9%, 9.2%). Two rare and threatened endemics, Hispaniolan Highland-Tanager (Xenoligea montana) and Western Chat-Tanager (Calyptophilus tertius), showed statistically significant declines, but we have low confidence in these findings because trends were driven by exceptionally high capture rates in 1997 and varied between sites. Analyses that excluded data from 1997 revealed no trend in capture rate over the course of the study. We found no evidence of temporal trends in capture rates for any other residents or Nearctic-Neotropical migrants. We do not know the causes of the observed declines, nor can we conclude that these declines are not a purely local phenomenon. However, our findings, along with other recent reports of declines in these same species, suggest that a closer examination of their conservation status is warranted. Given the difficulty in obtaining spatially extensive, long-term estimates of population change for Hispaniolan birds, we suggest focusing on other metrics of vulnerability that are more easily quantified yet remain poorly described, such as extent of occurrence.

scholarly journals Distribution, status and conservation of a Critically Endangered, extremely narrow endemic: Lamyropsis microcephala (Asteraceae) in Sardinia

Oryx ◽  
2011 ◽  
Vol 45 (2) ◽  
pp. 180-186 ◽  
Author(s):  
Giuseppe Fenu ◽  
Efisio Mattana ◽  
Gianluigi Bacchetta
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Integrated Approach ◽  
Critically Endangered ◽  
Ex Situ ◽  
Endemic Plant ◽  
Critically Endangered Species ◽  
Narrow Endemic ◽  
Conservation Measures ◽  
Endangered Status

AbstractThe aims of this work were to verify the distribution and population size of Lamyropsis microcephala (Asteraceae), characterize its habitat, assess its conservation status and initiate conservation measures for this Critically Endangered species. Distribution was determined by field surveys and mapping. To estimate population size and density 81 permanent monitoring plots were randomly established. Ex situ conservation measures were activated by harvesting and appropriate storage of seed. We confirmed the presence of L. microcephala at two previously known sites and found it in two previously unknown localities. The areas in which the species occur vary from 200 to 240,000 m2, at altitudes of 1,450–1,820 m, on slopes of 15–45° with aspects from north to west. The estimated number of ramets per population varied from c. 2,000 to c. 2,000,000, with a mean density of 8.29 ± SD 14.3 to 10.33 ± SD 10.05 ramets m-2. Our findings confirmed the Critically Endangered status of this species, although with different criteria. This study is an example of an integrated approach for the conservation of an extremely narrow endemic plant species and may be useful for other little-known threatened species for which urgent conservation measures are needed.

scholarly journals Conservation priorities in an endangered estuarine seahorse are informed by demographic history

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Thomas Kalama Mkare ◽  
Bettine Jansen van Vuuren ◽  
Peter R. Teske
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Demographic History ◽  
Conservation Status ◽  
Limited Range ◽  
The Other ◽  
Conservation Priorities ◽  
Population Declines ◽  
Term Survival

AbstractHistorical demographic events shape genetic diversity that remains evident in the genomes of contemporary populations. In the case of species that are of conservation concern, this information helps to unravel evolutionary histories that can be critical in guiding conservation efforts. The Knysna seahorse, Hippocampus capensis, is the world’s most endangered seahorse species, and it presently survives in only three estuaries on the South African south coast. Factors that contributed to the species becoming endangered are unclear; additionally, the lack of information on whether the three populations should be managed separately because of potential long-term isolation hampers effective management efforts. In the present study, we reconstructed the seahorses’ demographic history using a suite of microsatellite loci. We found that the largest population (Knysna Estuary) has colonised the other estuaries relatively recently (< 450 years ago), and that its population size is comparatively large and stable. Neither of the other two populations shows signs of long-term reductions in population size. The high conservation status of the species is thus a result of its limited range rather than historical population declines. Our findings indicate that the long-term survival of H. capensis depends primarily on the successful management of the Knysna population, although the other estuaries may serve as reservoirs of genetic diversity.

scholarly journals Assessing conservation status of resident and migrant birds on Hispaniola with constant-effort mist-netting

2015 ◽  
Author(s):  
John D Lloyd ◽  
Chris C Rimmer ◽  
Kent P McFarland
Keyword(s):  
Population Change ◽  
Conservation Status ◽  
Capture Rate ◽  
Temporal Trends ◽  
Bird Species ◽  
Quantitative Information ◽  
Neotropical Migrant ◽  
Migrant Birds ◽  
Conservation Assessments ◽  
Capture Rates

We analyzed temporal trends in mist-net capture rates of resident (n = 8) and overwintering Nearctic-Neotropical migrant (n = 3) bird species at two sites in montane broadleaf forest of the Sierra de Bahoruco, Dominican Republic, with the goal of providing quantitative information on population trends that could inform conservation assessments. We conducted sampling at least once annually during the winter months of January – March from 1997 – 2010. We found evidence of steep declines in capture rates for three resident species, including one species endemic to Hispaniola. Capture rate of Rufous-throated Solitaire (Myadestes genibarbis) declined by 3.9% per year (95% CL = 0%, 7.3%), Green-tailed Ground-Tanager (Microlegia palustris) by 6.8% (95% CL = 3.9%, 8.8%), and Greater Antillean Bullfinch (Loxigilla violacea) by 4.9% (95% CL = 0.9%, 9.2%). Two rare and threatened endemics, Hispaniolan Highland-Tanager (Xenolegia montana) and Western Chat-Tanager (Calyptophilus tertius), showed statistically significant declines, but we have low confidence in these findings because trends were driven by exceptionally high capture rates in 1997 and varied between sites. Analyses that excluded data from 1997 revealed no trend in capture rate over the course of the study. We found no evidence of temporal trends in capture rates for any other residents or Nearctic-Neotropical migrants. We do not know the causes of the observed declines, nor can we conclude that these declines are not a purely local phenomenon. However, our findings, along with other recent reports of declines in these same species, suggest that a closer examination of their conservation status is warranted. Given the difficulty in obtaining spatially extensive, long-term estimates of population change for Hispaniolan birds, we suggest focusing on other metrics of vulnerability that are more easily quantified yet remain poorly described, such as extent of occurrence.

scholarly journals The state of breeding birds in Greece: trends, threats, and implications for conservation

2020 ◽  
pp. 1-15
Author(s):  
DIMITRIOS VAVYLIS ◽  
ANASTASIOS BOUNAS ◽  
GEORGIOS KARRIS ◽  
KOSTAS A. TRIANTIS
Keyword(s):  
Population Change ◽  
Conservation Status ◽  
Global Scale ◽  
Iucn Red List ◽  
Red List ◽  
Breeding Birds ◽  
Ecosystem Functions ◽  
Population Declines ◽  
Population Size Estimates ◽  
Declining Populations

Summary Birds are suffering from steep population declines on a global scale and they are one of the few taxonomic groups for which these declines are well documented by long-term monitoring data. This study provides a synthesis of the status of the breeding birds of Greece. To this aim, we retrieved population size estimates from six sources spanning 22 years (1992–2014) and calculated species’ trends in Greece. Using the IUCN Red List assessments for each species we assessed whether ecological traits including habitat and diet preferences were associated with species’ trends and conservation status in Europe and determined major threats affecting birds in Greece. Moreover, we assessed the importance of Important Bird & Biodiversity Areas (IBAs) in terms of declining trigger species. Results showed that almost one fifth of the breeding birds in Greece have declining populations. Raptors were found to be the most threatened group of birds whereas the highest declines by dietary group were observed in scavengers, with 60% of species showing a decreasing trend. The most common threats were those that cause habitat alteration and degradation as well as more direct effects such as poisoning. Our results suggest that restoration of habitat and ecosystem functions along with the management of protected areas and improvement of legislation should be the main conservation actions undertaken and pinpointed the IBAs where they should be prioritized for implementation. Finally, further research, especially on specific drivers of population change, along with further examination of current and past population trends, will increase the power and accuracy of future regional Red List assessments especially concerning the breeding species for which the country bears the greatest responsibility.

scholarly journals Demography of Zenaida Doves on Cayo Del Agua, Culebra, Puerto Rico

The Condor ◽  
2002 ◽  
Vol 104 (3) ◽  
pp. 587-597 ◽  
Author(s):  
Frank F. Rivera-Milán ◽  
Fred C. Schaffner
Keyword(s):  
Puerto Rico ◽  
Reproductive Success ◽  
Population Size ◽  
Field Data ◽  
Nest Density ◽  
Apparent Survival ◽  
Zenaida Aurita ◽  
Annual Changes ◽  
Time Specific ◽  
Capture Rates

AbstractThe demography of Zenaida Doves (Zenaida aurita) was studied on Cayo del Agua, Culebra, Puerto Rico. We collected capture-recapture and reproductive success data and monitored annual changes in the density of ground nests in 1987–1993 and 2000. Models with time-specific apparent survival and constant capture rates (ϕ̂t, p̂c) and constant apparent survival and time-specific capture rates (ϕ̂c, p̂t) were equally parsimonious, with the former having 1.5 times more support from the data. Rainfall of the first six months of the year was positively related to nest density, and crab density was negatively related to nesting success and the number of doves fledged per nest. Crabs are the main predators of dove nests on Cayo del Agua. Models, parameterized with field data, were used to simulate full and reduced stochastic variation in environmental and demographic conditions, and predict annual changes in population size. High recruitment (births or births + immigrants) offset high losses (deaths + emigrants) in all instances. Our field data suggest that Zenaida Doves suffered an ecological crunch between 1989 and 1990, when weather (a hurricane followed by a drought), food availability, and nest predation interacted, lowering the number of locally fledged doves that survived the hatching year (1989–1990) and reproductive success (1990). Under severe conditions, population size and recovery mainly depended on immigration. Apparent survival returned to pre-hurricane levels between 1990 and 1991, and reproductive success was about average in 1991.Demografía de Zenaida aurita en Cayo del Agua, Culebra, Puerto RicoResumen. Estudiamos la demografía de Zenaida aurita en Cayo del Agua, Culebra, Puerto Rico. Durante 1987–1993 y 2000 colectamos datos de captura-recaptura y éxito reproductivo y seguimos los cambios anuales en la densidad de nidos localizados en el suelo. Los modelos con tasa de supervivencia aparente específica para cada período de tiempo, y tasa de captura constante (ϕ̂t, p̂c), y con tasas de supervivencia aparente constante y captura específica para cada período de tiempo (ϕ̂c, p̂t) tuvieron igual parsimonia, aunque el primer modelo fue apoyado por los datos 1.5 veces más que el segundo modelo. La lluvia de los primeros seis meses del año se relacionó positivamente con la densidad de los nidos, y la densidad de los cangrejos se relacionó negativamente con el éxito de nidificación y el número de individuos producidos por nido. Los cangrejos son los principales depredadores de los nidos de Z. aurita en Cayo del Agua. Usamos modelos, con estimados de parámetros basados en los datos de campo, para simular diferentes niveles de variación estocástica en las condiciones ambientales y demográficas, y para predecir cambios anuales en el tamaño poblacional. El reclutamiento (nacimientos o nacimientos + inmigrantes) superó a la pérdida (muertes + emigrantes) de individuos en todo momento. Nuestros datos de campo sugieren que Z. aurita sufrió un gran impacto ecológico entre 1989 y 1990, cuando las condiciones climáticas (un huracán seguido de una sequía), la disponibilidad de alimento, y la depredación de nidos interactuaron, disminuyendo el número de individuos que sobrevivieron el primer año de vida (1989–1990) y el éxito reproductivo (1990). Bajo condiciones severas, el tamaño de la población y su recuperación dependió mayormente de la inmigración. La supervivencia aparente regresó al mismo nivel que antes del huracán entre 1990 y 1991, y el éxito reproductivo se acercó a un nivel promedio en 1991.

scholarly journals Press-Pulse Odocoileus Virginianus Herbivory in Relict Tsuga Canadensis Stands in the Western Upper Peninsula of Michigan, USA

Forests ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 496
Author(s):  
Grace L. Parikh ◽  
Christopher R. Webster
Keyword(s):  
Odocoileus Virginianus ◽  
Polar Vortex ◽  
Tsuga Canadensis ◽  
Forest Community ◽  
Population Declines ◽  
Upper Peninsula ◽  
Deer Population ◽  
High Severity ◽  
Substantial Decline ◽  
Upper Peninsula Of Michigan

Ungulate herbivory occurring within a forest plant community’s natural range of variation may help maintain species diversity. However, acute or chronically elevated levels of herbivory can produce dramatic changes in forest communities. For example, chronically high levels of herbivory by white-tailed deer (Odocoileus virginianus Zimmerman) in regions of historically low abundance at northern latitudes have dramatically altered forest community composition. In eastern hemlock (Tsuga canadensis L. Carrière) stands where deer aggregate during winter, high deer use has been associated with a shift towards deciduous species (i.e., maples [Acer spp.]) dominating the regeneration layer. Especially harsh winters can lead to deer population declines, which could facilitate regeneration of species that have been suppressed by browsing, such as hemlock. To enhance our understanding of how fluctuations in herbivory influence regeneration dynamics, we surveyed regeneration and deer use in 15 relict hemlock stands in the western Upper Peninsula of Michigan in 2007 and again in 2015. With the exception of small seedlings (0.04–0.24 m height), primarily maples whose abundance increased significantly (p < 0.05), we observed widespread significant declines (p < 0.05) in the abundance of medium (0.25 ≤ 1.4 m height) and large regeneration (>1.4 m tall ≤ 4 cm diameter at breast height) over the study period. Midway through our study period, the region experienced a high severity winter (i.e., “polar vortex”) which resulted in a substantial decline in the white-tailed deer population. Given the dominance of maples and dearth of hemlock in the seedling layer, the decline in the deer population may fail to forestall or possibly hasten the trend towards maple dominance of the regeneration layer as these stands recover from pulses of acute herbivory associated with high-severity winters and the press of chronically high herbivory that precedes them.

scholarly journals Giant otter Pteronura brasiliensis density and abundance in Llanos Orientales de Colombia in the Orinoco basin

Oryx ◽  
2020 ◽  
pp. 1-4
Author(s):  
Germán Garrote ◽  
Beyker Castañeda ◽  
Jose Manuel Escobar ◽  
Laura Pérez ◽  
Brayan Marín ◽  
...  
Keyword(s):  
South America ◽  
Population Size ◽  
20Th Century ◽  
Conservation Status ◽  
Species Conservation ◽  
Iucn Red List ◽  
Red List ◽  
Recreational Fishing ◽  
Pteronura Brasiliensis ◽  
Direct Counts

Abstract The giant otter Pteronura brasiliensis, categorized as Endangered on the IUCN Red List, was once widely distributed throughout South America. By the middle of the 20th century the giant otter had become locally extinct along the main rivers of the Orinoco basin. Although some populations seem to have recovered, the paucity of information available does not permit a full evaluation of the species' conservation status. The objective of this study was to estimate the abundance and density of the giant otter population along the Orinoco river in the municipality of Puerto Carreño, Vichada, Colombia, where there is important commercial and recreational fishing. Thirty-nine linear km were surveyed, repeatedly, with a total of 315 km of surveys. Population size was estimated by direct counts of individuals. All individuals detected were photographed and identified individually from their throat pelage patterns. In total, 30 otters were identified, giving a minimum density of 0.77 individuals per km, one of the highest reported for the species in Colombia. Given the high density in this well-developed area, our results highlight the importance of this population for the conservation of the species.

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