Community modeling reveals the importance of elevation and land cover in shaping migratory bird abundance in the Andes.

The tropical Andes are characterized by extreme topographic and climatic complexity, which has likely contributed to their outstanding current species diversity, composed of many range-restricted species. However, little is known about how the distribution and abundance of highly mobile organisms, like long-distance migratory birds, varies across different land covers, elevations, and climatic conditions within the Andes. We conducted 1,606 distance-sampling point counts across the Colombian Andes, spanning elevations from 253 to 3,708 m, a range of precipitation regimes and representative land covers. We then employed a novel application of a multispecies hierarchical modeling approach to evaluate how elevation, local land cover, aboveground woody biomass, cloud cover, precipitation, and seasonality in precipitation shape the abundance of the migratory land bird community in the Andes. We detected 1,824 individuals of 29 species of migratory land birds, six of which were considered incidental in our study region. We modeled the abundance of the remaining 23 species, while considering observer and time of day effects on detectability. We found that both elevation and land cover had an overriding influence on the abundance of migratory species across the Andes, with strong evidence for a mid-elevation peak in abundance, and species-specific responses to both variables. As a community, migratory birds had the highest mean abundance in shade coffee plantations, secondary forest, and mature forest. Aboveground woody biomass did not affect the abundance of all species as a group, but a few showed strong responses to this variable. Contrary to predictions of a positive correlation between abundance and precipitation, we found no evidence for community-level responses to precipitation, aside for a weak tendency for birds to select areas with intermediate levels of precipitation. This novel use of a multispecies model sheds new light on the mechanisms shaping the winter distribution of migratory birds and highlights the importance of elevation and land cover types over climatic variables in the context of the Colombian Andes.

Population density estimates for three endangered bird taxa from the Pernambuco Endemism Center, northeastern Brazil / Estimativas de densidade populacional em três táxons de aves ameaçados de extinção do Centro de Endemismo Pernambuco, nordeste do Brasil

Abstract Determining the relative risks of extinction of declining taxa is important to delineate conservation priorities and to guide the investments in conservation. Brazil concentrates the greatest number of endangered avian taxa on Earth, yet demographic information is lacking for most of them. Here we present distance-sampling population density estimates for three endangered bird taxa endemic to the Pernambuco Endemism Center (PEC), the most critically disturbed Atlantic Forest region. The analyzed taxa were the White-shouldered Antshrike Thamnophilus aetiops distans (Endangered), the Brown-winged Mourner Schiffornis turdina intermedia (Vulnerable), and the White-bellied Tody-tyrant Hemitriccus griseipectus naumburgae (Vulnerable). The estimated numbers of individuals/ha in an approximately 1,000 ha forest fragment were 0.21, 0.14, and 0.73, respectively. Our findings corroborated the premise that even taxa classified in similar threat categories based on habitat characteristics alone can have different population densities and consequently, divergent risks of extinction. Although population densities can vary among fragments, the extrapolation of our data to the whole PEC confirmed the Vulnerable status of the Brown-winged Mourner, and indicated the Vulnerable and Least Concern categories for the White-shouldered Antshrike and for the White-bellied Tody-tyrant, suggesting that for the two later taxa, the current classifications (Endangered and Vulnerable) based on their Areas of Occupancy must prevail.

Resumo A determinação dos riscos relativos de extinção dos táxons ameaçados é importante para o delineamento de ações de recuperação e para o direcionamento dos investimentos em conservação. O Brasil é o país que possui o maior número de táxons ameaçados de aves, no entanto, informações sobre aspectos demográficos são inexistentes para a maioria deles. Neste trabalho são apresentadas estimativas de densidades populacionais, baseadas no método de amostragem por distância, para três táxons ameaçados de extinção endêmicos do Centro de Endemismo Pernambuco (CEP), a região mais degradada de toda a Mata Atlântica. Os táxons analisados foram a choca-lisa Thamnophilus aetiops distans (Ameaçada), o flautim-marrom Schiffornis turdina intermedia (Vulnerável) e a maria-de-barriga-branca Hemitriccus griseipectus naumburgae (Vulnerável). Os números de indivíduos/ha estimados para um fragmento de floresta de aproximadamente 1000 ha foram respectivamente 0,21, 0,14 e 0,73. Com isto, foi possível confirmar a premissa de que mesmo táxons classificados em uma mesma categoria de ameaça com base apenas em informações de hábitats podem possuir densidades populacionais bastante divergentes e portanto diferentes graus de riscos de extinção. Embora as densidades populacionais possam variar entre fragmentos, a extrapolação destes dados para toda a área do CEP confirmou a classificação de Vulnerável para o flautim-marrom e indicou as categorias Vulnerável e Pouco Preocupante para a choca-lisa e para a maria-de-barriga-branca, sugerindo que para as duas últimas, as classificações atuais baseadas nos tamanhos das suas Áreas de Ocupação (Ameaçada e Vulnerável) devem prevalecer.

Free-Roaming Dog Surveys in Quito, Ecuador: Experiences, Lessons Learned, and Future Work.

The selection of a survey method of free-roaming dog populations should be based on analyses of local capacities and management priorities. Here, we compare the results of surveys of the stray dog population in Quito, Ecuador, using two different methodologies and propose an alternative method for future surveys in the city. We carried out all surveys in ~5 km-transects in a sample of eight urban and eight rural parishes (16 transects total). In 2018, we used the capture-recapture method to estimate absolute population size and 95% CI. We began transect surveys at 04 h 00 (local time) and identified individuals with photographs. The main limitations of this method were errors in identifying individuals, since photographs were not always clear, partly due to low light conditions during the surveys. This method also required more time and more complex logistics. In 2019, we used distance sampling to estimate population density and began the surveys at 08 h 00 (local time). Errors in the estimation of animal-observer distances and angles were our main concern when using this method. For future surveys, we propose to carry out direct observations of dog abundance (number of free-roaming dogs/km) during street counts, complemented with capture-recapture surveys every 5 years. This alternative method albeit simple, is sensitive enough to (1) provide local authorities with objective assessments of management interventions, (2) better understanding the dynamics of free-roaming dog populations and (3) increasing public awareness about the problem of pet abandonment through citizen participation in the surveys.

A high-diversity primate community in a mid-elevation flooded forest, the Jungla de Los Monos Community Reserve, Peru.

The Alto Mayo region in the Peruvian department of San Martin has one of the highest levels of deforestation and fragmentation in the country. Historically, San Martin was home to at least 20 primate species, of which at least 14 persist in the Alto Mayo Valley. We surveyed primate populations in the "Jungla de Los Monos", a locally protected remnant of a naturally diverse primate community in one of the last remaining mid-elevation (800 m a.s.l.) seasonally flooded forests in the region. We recorded seven primate species, with a further two species reported to have been extirpated from the area. By far the most common species was Saimiri macrodon. Half of the primate biomass was made up of a single species, Alouatta seniculus, with S. macrodon accounting for another quarter. The endemic Plecturocebus oenanthe was only detected once in forest interior, but was observed in edge and riverine forest, as well as neighboring fragments. The area holds a surprisingly high diversity and density of primates considering its proximity to population centers, thanks primarily to self-imposed hunting bans and logging control by local communities.

Common opossum population density in an agroforestry system in Bolivia

The common opossum, Didelphis marsupialis thrives near human settlements. Understanding its ecology could help planning management decisions about this species, especially in anthropogenic landscapes. Yet, there are no density estimations for this species throughout its distribution range in Bolivia. We estimated the density of D. marsupialis in a rural agricultural community, where agroforestry plantations and fallows cover most of the land. We counted individuals in line transects and used DISTANCE software to calculate density. We covered a total of 70.21 km in 143 night counts, obtaining 38 records of D. marsupialis. We estimated a density of 0.30 individuals ha-1 (SE = 0.062; range: 0.20 - 0.45 individuals ha-1), with a mean encounter rate of 0.54 individuals km-1. Encounter rate varied between habitats, with mean values of 0.20 in secondary forests and 0.64 in agroforestry plantations. Our density estimate is near the lower range of previously reported values for the common opossum in other countries. We argue that our results may reflect the response to the availability of food resources and predation pressure in agroforestry plantations. (AU)

Encounter rate and behavior of Alouatta guariba clamitans in the Ilha Grande State Park, Rio de Janeiro state, Brazil

Alouatta guariba clamitans Cabrera, 1940 is an endemic species of the Atlantic Forest that occurs from south Bahia, Brazil, extending south to the province of Misiones, Argentina. In Rio de Janeiro state, the species was classified as threatened, indicating that attention is needed for the conservation of this taxon. Additionally, an outbreak of yellow fever spread throughout the southeastern states of Brazil from January 2017 until March 2018 seriously threatening Rio de Janeiro populations of the species. Herein, we aimed to provide the first estimates of A. g. clamitans encounter rate, density, and population size in the Ilha Grande State Park (PEIG), which is part of the Atlantic Forest biome of Brazil. Data were collected in two different periods, the first between December 2003 and May 2005, and the second from August 2009 to May 2010, and information on encounter rates and behavior was collected to better understand aspects of species ecology. The estimated encounter rate in the first period through the distance sampling method was 0.04 ± 0.01 individuals per kilometer. Nine groups were recorded in the second period of the study, with 47 individuals along 3 km. Our estimates of encounter rate, density and population size were low and reinforces the need to initiate species monitoring and assess the impact that yellow fever outbreaks may have on PEIG populations. The results presented here can be a starting point to support future strategic actions for the species, to measure impacts and to the management of the species, and for a conservation program.(AU)

Encounter rate and behavior of Alouatta guariba clamitans in the Ilha Grande State Park, Rio de Janeiro state, Brazil

Alouatta guariba clamitans Cabrera, 1940 is an endemic species of the Atlantic Forest that occurs from south Bahia, Brazil, extending south to the province of Misiones, Argentina. In Rio de Janeiro state, the species was classified as threatened, indicating that attention is needed for the conservation of this taxon. Additionally, an outbreak of yellow fever spread throughout the southeastern states of Brazil from January 2017 until March 2018 seriously threatening Rio de Janeiro populations of the species. Herein, we aimed to provide the first estimates of A. g. clamitans encounter rate, density, and population size in the Ilha Grande State Park (PEIG), which is part of the Atlantic Forest biome of Brazil. Data were collected in two different periods, the first between December 2003 and May 2005, and the second from August 2009 to May 2010, and information on encounter rates and behavior was collected to better understand aspects of species’ ecology. The estimated encounter rate in the first period through the distance sampling method was 0.04 ± 0.01 individuals per kilometer. Nine groups were recorded in the second period of the study, with 47 individuals along 3 km. Our estimates of encounter rate, density and population size were low and reinforces the need to initiate species monitoring and assess the impact that yellow fever outbreaks may have on PEIG populations. The results presented here can be a starting point to support future strategic actions for the species, to measure impacts and to the management of the species, and for a conservation program.

Common opossum population density in an agroforestry system in Bolivia / Densidad de carachupas en un sistema agroforestal de Bolivia

La carachupa, Didelphis marsupialis prospera cerca de asentamientos humanos. Entender la ecología de una población puede ayudar a tomar decisiones de manejo de esta especie, especialmente en paisajes antropogénicos. Sin embargo, no existen estimaciones de la densidad de esta especie en todo su rango de distribución en Bolivia. Este estudio estimó la densidad de D. marsupialis en una comunidad agrícola, donde los sistemas agroforestales y barbechos cubren la mayoría de la tierra. Empleamos conteos en transectos lineales y usamos el programa DISTANCE para calcular la densidad. En total recorrimos 70.21 km en 143 noches de conteo y obtuvimos 38 registros de D. marsupialis. Estimamos una densidad de 0.30 individuos ha-1 (SE = 0.062; rango: 0.20 - 0.45 individuos ha-1) y una tasa de encuentro promedio de 0.54 individuos km-1. La tasa de encuentro varió entre hábitats, con valores promedio de 0.2 para bosque secundario y 0.64 para sistemas agroforestales. Nuestra estimación de densidad se encuentra cerca de los valores más bajos antes reportados para la especie en otros países. Creemos que nuestros resultados reflejan la respuesta a la disponibilidad de recursos en sistemas agroforestales y la presión de depredación en nuestro sitio de estudio.(AU)

The common opossum, Didelphis marsupialis thrives near human settlements. Understanding its ecology could help planning management decisions about this species, especially in anthropogenic landscapes. Yet, there are no density estimations for this species throughout its distribution range in Bolivia. We estimated the density of D. marsupialis in a rural agricultural community, where agroforestry plantations and fallows cover most of the land. We counted individuals in line transects and used DISTANCE software to calculate density. We covered a total of 70.21 km in 143 night counts, obtaining 38 records of D. marsupialis. We estimated a density of 0.30 individuals ha-1 (SE = 0.062; range: 0.20 - 0.45 individuals ha-1), with a mean encounter rate of 0.54 individuals km-1. Encounter rate varied between habitats, with mean values of 0.20 in secondary forests and 0.64 in agroforestry plantations. Our density estimate is near the lower range of previously reported values for the common opossum in other countries. We argue that our results may reflect the response to the availability of food resources and predation pressure in agroforestry plantations.(AU)

Long-term population monitoring of the threatened and endemic black-headed squirrel monkey (Saimiri vanzolinii) shows the importance of protected areas for primate conservation in Amazonia.

Population monitoring of endangered species is essential to the improvement of their management and conservation plans. The black-headed squirrel monkey (Saimiri vanzolinii) is a vulnerable species on the IUCN Red List and has extreme geographical endemism, exhibiting the smallest known distribution among Neotropical primates (ca. 870 km2 ), over 90% of which occurs in white-water flooded forests within the Mamirauá Sustainable Development Reserve (MSDR), Brazilian Amazonia. To assess the effectiveness of this protected area in conserving the species, we conducted population monitoring of black-headed squirrel monkeys across five consecutive years (2009-2013) on nine trails 2 km each. Each year samples included both low and high river water periods. We used the distance sampling method, recording the distance to each observed social group as well as counting component individuals. We also calculated annual encounter rates based on the number of individuals sighted every 10 km traveled. Densities ranged from 256 individuals/km2 (2011) to 453 individuals/km2 (2013), and no seasonal differences were detected. Population size was estimated to be 147,848 mature individuals. Encounter rates ranged from 100 individuals/10 km (2010) to 179 individuals/10 km (2013); no significant difference among years was found. We found that S. vanzolinii populations remained stable throughout the years, which indicates that the MSDR has been playing an essential role on protecting this species. Due to difficulties of fulfilling assumptions of the distance sampling method, we consider the encounter rate analysis to be more effective for monitoring this and other Saimiri species. Given the critical endemism and worrying conservation status of S. vanzolinii, we suggest that monitoring of the species population should be carried out regularly.

Assessing the population density of the spotted paca, Cuniculus paca, (Rodentia: Cuniculidae) on an Atlantic Forest island, southeastern Brazil

The spotted paca, Cuniculus paca (Linnaeus, 1766), is a Neotropical, opportunistic, frugivorous caviomorph rodent, that inhabits primarily broadleaf forests. We aimed to provide the first estimates of density of C. paca for the Ilha Grande, an island located in the Atlantic Rain Forest biome of Brazil. Density and population size were estimated using the total number of individuals observed along each trail through the program DISTANCE 7. Our estimates of density and population size reinforces the importance of the Ilha Grande as an important reservoir of the species. Therefore, the results presented herein can be a starting point to support future action plans for the species, making predictions regarding the ecosystem and management and conservation of the spotted paca. Furthermore, the results can be used as a surrogate for other regions in which the species occurs.

Assessing the population density of the spotted paca, Cuniculus paca, (Rodentia: Cuniculidae) on an Atlantic Forest island, southeastern Brazil

The spotted paca, Cuniculus paca (Linnaeus, 1766), is a Neotropical, opportunistic, frugivorous caviomorph rodent, that inhabits primarily broadleaf forests. We aimed to provide the first estimates of density of C. paca for the Ilha Grande, an island located in the Atlantic Rain Forest biome of Brazil. Density and population size were estimated using the total number of individuals observed along each trail through the program DISTANCE 7. Our estimates of density and population size reinforces the importance of the Ilha Grande as an important reservoir of the species. Therefore, the results presented herein can be a starting point to support future action plans for the species, making predictions regarding the ecosystem and management and conservation of the spotted paca. Furthermore, the results can be used as a surrogate for other regions in which the species occurs.(AU)

Biological traits, rather than environment, shape detection curves of large vertebrates in neotropical rainforests.

Line transect surveys are widely used in Neotropical rainforests to estimate the population abundance of medium- and large-sized vertebrates. The use of indices such as encounter rate has been criticized because the probability of animal detection may fluctuate due to the heterogeneity of environmental conditions among sites. In addition, the morphological and behavioral characteristics (biological traits) of species affect their detectability. In this study, we compared the extent to which environmental conditions and species' biological traits bias abundance estimates in terra firme rainforests in French Guiana. The selected environmental conditions included both physical conditions and forest structure covariates, while the selected biological traits included the morphological and behavioral characteristics of species. We used the distance sampling method to model the detection probability as an explicit function of environmental conditions and biological traits and implemented a model selection process to determine the relative importance of each group of covariates. Biological traits contributed to the variability of animal detectability more than environmental conditions, which had only a marginal effect. Detectability was best for large animals with uniform or disruptive markings that live in groups in the canopy top. Detectability was worst for small, solitary, terrestrial animals with mottled markings. In the terra firme rainforests that represent ~80% of the Amazonia and Guianas regions, our findings support the use of relative indices such as the encounter rate to compare population abundance between sites in species-specific studies. Even though terra firme rainforests may appear similar between regions of Amazonia and the Guianas, comparability must be ensured, especially in forests disturbed by human activity. The detection probability can be used as an indicator of species' vulnerability to hunting and, thus, to the risk of local extinction. Only a few biological trait covariates are required to correctly estimate the detectability of the majority of medium- and large-sized vertebrates. Thus, a biological trait model could be useful in predicting the detection probabilities of rare, uncommon, or localized species for which few data are available to fit the detection function.

Fruit availability drives the distribution of a folivorous-frugivorous primate within a large forest remnant.

Understanding the ecological factors that influence the presence, abundance, and distribution of species within their habitats is critical for ensuring their long-term conservation. In the case of primary consumers, such as most primates, the availability and richness of plant foods are considered key drivers of population density at these variables influence the spatial distribution of social units within a finer, habitat patch level scale. We tested the hypothesis that the spatiotemporal availability and richness of plant foods, drive the spatial distribution of brown howler monkeys (Alouatta guariba clamitans) at a fine spatial scale. We established five line transects (2.6-4.3 km long) to census the population of brown howlers in Morro São Pedro, a 1,200 ha Atlantic forest remnant in southern Brazil, every 2 weeks from January to June 2015. We used data from tree inventories performed in sighting and control plots, and phenological surveys of 17 top food tree species to estimate bi-weekly food availability. We recorded a total of 95 sightings. The number of sightings per sampling period ranged from 2 to 12. The availability of fruit (ripe and unripe) was higher in sighting than in control plots, whereas leaf availability and the richness of food tree species was similar. We conclude that the spatial distribution of fruiting trees and the availability of fruit drive the pattern of habitat use, and spacing of brown howler groups in Morro São Pedro.

Accessing camera trap survey feasibility for estimating Blastocerus dichotomus (Cetartiodactyla, Cervidae) demographic parameters / Avaliação da viabilidade do uso de armadilhas fotográficas para estimar parâmetros demográficos de Blastocerus dichotomus (Cetartiodactyla, Cervidae)

Demographic information is the basis for evaluating and planning conservation strategies for an endangered species. However, in numerous situations there are methodological or financial limitations to obtain such information for some species. The marsh deer, an endangered Neotropical cervid, is a challenging species to obtain biological information. To help achieve such aims, the study evaluated the applicability of camera traps to obtain demographic information on the marsh deer compared to the traditional aerial census method. Fourteen camera traps were installed for three months on the Capão da Cruz floodplain, in state of São Paulo, and ten helicopter flyovers were made along a 13-kilometer trajectory to detect resident marsh deer. In addition to counting deer, the study aimed to identify the sex, age group and individual identification of the antlered males recorded. Population estimates were performed using the capture-mark-recapture method with the camera trap data and by the distance sampling method for aerial observation data. The costs and field efforts expended for both methodologies were calculated and compared. Twenty independent photographic records and 42 sightings were obtained and generated estimates of 0.98 and 1.06 ind/km², respectively. In contrast to the aerial census, camera traps allowed us to individually identify branch-antlered males, determine the sex ratio and detect fawns in the population. The cost of camera traps was 78% lower but required 20 times more field effort. Our analysis indicates that camera traps present a superior cost-benefit ratio compared to aerial surveys, since they are more informative, cheaper and offer simpler logistics. Their application extends the possibilities of studying a greater number of populations in a long-term monitoring.(AU)

Informações demográficas constituem a base para a avaliação e planejamento de estratégias de conservação de uma espécie ameaçada. No entanto, em muitas situações existem limitações metodológicas ou financeiras para a obtenção de tais informações para algumas espécies. O cervo-do-pantanal, um cervídeo neotropical ameaçado de extinção, é uma espécie desafiadora para obtenção de informações biológicas. Para suprir essa demanda, o presente trabalho avaliou a aplicabilidade das armadilhas fotográficas para obtenção de informações demográficas de cervo-do-pantanal em comparação com o tradicional método de censo aéreo. Na várzea Capão da Cruz, Estado de São Paulo, foram instaladas 14 armadilhas fotográficas durante três meses e realizados dez sobrevoos de helicóptero num trajeto de 13 km para detecção dos cervos-do-pantanal ali residentes. Além da contagem dos animais, objetivou-se identificar o sexo, a faixa etária e a identificação individual dos machos galhados registrados. As estimativas populacionais foram realizadas pelo método de captura-marcação-recaptura com os dados de armadilhas fotográficas e pelo método de amostragem por distâncias para os dados de observação aérea. Foram contabilizados e ponderados os custos e esforços de campo despendidos para ambas metodologias. Obteve-se 20 registros fotográficos independentes e 42 visualizações que geraram estimativas de 0,98 e 1,06 ind./km² respectivamente. Ao contrário do censo aéreo, as armadilhas fotográficas permitiram a identificação individual dos machos galhados, a proporção sexual e a detecção de filhotes na população. O custo das armadilhas fotográficas foi 78% menor, porém demandou um esforço de campo 20 vezes maior. Avaliamos que as armadilhas fotográficas apresentaram uma relação custo-benefício superiores em relação aos levantamentos aéreos, por ser mais informativa e barata e com uma logística mais simples. Sua aplicação abre a [...](AU)

Accessing camera trap survey feasibility for estimating Blastocerus dichotomus (Cetartiodactyla, Cervidae) demographic parameters / Avaliação da viabilidade do uso de armadilhas fotográficas para estimar parâmetros demográficos de Blastocerus dichotomus (Cetartiodactyla, Cervidae)

Demographic information is the basis for evaluating and planning conservation strategies for an endangered species. However, in numerous situations there are methodological or financial limitations to obtain such information for some species. The marsh deer, an endangered Neotropical cervid, is a challenging species to obtain biological information. To help achieve such aims, the study evaluated the applicability of camera traps to obtain demographic information on the marsh deer compared to the traditional aerial census method. Fourteen camera traps were installed for three months on the Capão da Cruz floodplain, in state of São Paulo, and ten helicopter flyovers were made along a 13-kilometer trajectory to detect resident marsh deer. In addition to counting deer, the study aimed to identify the sex, age group and individual identification of the antlered males recorded. Population estimates were performed using the capture-mark-recapture method with the camera trap data and by the distance sampling method for aerial observation data. The costs and field efforts expended for both methodologies were calculated and compared. Twenty independent photographic records and 42 sightings were obtained and generated estimates of 0.98 and 1.06 ind/km², respectively. In contrast to the aerial census, camera traps allowed us to individually identify branch-antlered males, determine the sex ratio and detect fawns in the population. The cost of camera traps was 78% lower but required 20 times more field effort. Our analysis indicates that camera traps present a superior cost-benefit ratio compared to aerial surveys, since they are more informative, cheaper and offer simpler logistics. Their application extends the possibilities of studying a greater number of populations in a long-term monitoring.

Informações demográficas constituem a base para a avaliação e planejamento de estratégias de conservação de uma espécie ameaçada. No entanto, em muitas situações existem limitações metodológicas ou financeiras para a obtenção de tais informações para algumas espécies. O cervo-do-pantanal, um cervídeo neotropical ameaçado de extinção, é uma espécie desafiadora para obtenção de informações biológicas. Para suprir essa demanda, o presente trabalho avaliou a aplicabilidade das armadilhas fotográficas para obtenção de informações demográficas de cervo-do-pantanal em comparação com o tradicional método de censo aéreo. Na várzea Capão da Cruz, Estado de São Paulo, foram instaladas 14 armadilhas fotográficas durante três meses e realizados dez sobrevoos de helicóptero num trajeto de 13 km para detecção dos cervos-do-pantanal ali residentes. Além da contagem dos animais, objetivou-se identificar o sexo, a faixa etária e a identificação individual dos machos galhados registrados. As estimativas populacionais foram realizadas pelo método de captura-marcação-recaptura com os dados de armadilhas fotográficas e pelo método de amostragem por distâncias para os dados de observação aérea. Foram contabilizados e ponderados os custos e esforços de campo despendidos para ambas metodologias. Obteve-se 20 registros fotográficos independentes e 42 visualizações que geraram estimativas de 0,98 e 1,06 ind./km² respectivamente. Ao contrário do censo aéreo, as armadilhas fotográficas permitiram a identificação individual dos machos galhados, a proporção sexual e a detecção de filhotes na população. O custo das armadilhas fotográficas foi 78% menor, porém demandou um esforço de campo 20 vezes maior. Avaliamos que as armadilhas fotográficas apresentaram uma relação custo-benefício superiores em relação aos levantamentos aéreos, por ser mais informativa e barata e com uma logística mais simples. Sua aplicação abre a [...]

Accessing camera trap survey feasibility for estimating Blastocerus dichotomus (Cetartiodactyla, Cervidae) demographic parameters

ABSTRACT Demographic information is the basis for evaluating and planning conservation strategies for an endangered species. However, in numerous situations there are methodological or financial limitations to obtain such information for some species. The marsh deer, an endangered Neotropical cervid, is a challenging species to obtain biological information. To help achieve such aims, the study evaluated the applicability of camera traps to obtain demographic information on the marsh deer compared to the traditional aerial census method. Fourteen camera traps were installed for three months on the Capão da Cruz floodplain, in state of São Paulo, and ten helicopter flyovers were made along a 13-kilometer trajectory to detect resident marsh deer. In addition to counting deer, the study aimed to identify the sex, age group and individual identification of the antlered males recorded. Population estimates were performed using the capture-mark-recapture method with the camera trap data and by the distance sampling method for aerial observation data. The costs and field efforts expended for both methodologies were calculated and compared. Twenty independent photographic records and 42 sightings were obtained and generated estimates of 0.98 and 1.06 ind/km², respectively. In contrast to the aerial census, camera traps allowed us to individually identify branch-antlered males, determine the sex ratio and detect fawns in the population. The cost of camera traps was 78% lower but required 20 times more field effort. Our analysis indicates that camera traps present a superior cost-benefit ratio compared to aerial surveys, since they are more informative, cheaper and offer simpler logistics. Their application extends the possibilities of studying a greater number of populations in a long-term monitoring.

RESUMO Informações demográficas constituem a base para a avaliação e planejamento de estratégias de conservação de uma espécie ameaçada. No entanto, em muitas situações existem limitações metodológicas ou financeiras para a obtenção de tais informações para algumas espécies. O cervo-do-pantanal, um cervídeo neotropical ameaçado de extinção, é uma espécie desafiadora para obtenção de informações biológicas. Para suprir essa demanda, o presente trabalho avaliou a aplicabilidade das armadilhas fotográficas para obtenção de informações demográficas de cervo-do-pantanal em comparação com o tradicional método de censo aéreo. Na várzea Capão da Cruz, Estado de São Paulo, foram instaladas 14 armadilhas fotográficas durante três meses e realizados dez sobrevoos de helicóptero num trajeto de 13 km para detecção dos cervos-do-pantanal ali residentes. Além da contagem dos animais, objetivou-se identificar o sexo, a faixa etária e a identificação individual dos machos galhados registrados. As estimativas populacionais foram realizadas pelo método de captura-marcação-recaptura com os dados de armadilhas fotográficas e pelo método de amostragem por distâncias para os dados de observação aérea. Foram contabilizados e ponderados os custos e esforços de campo despendidos para ambas metodologias. Obteve-se 20 registros fotográficos independentes e 42 visualizações que geraram estimativas de 0,98 e 1,06 ind./km² respectivamente. Ao contrário do censo aéreo, as armadilhas fotográficas permitiram a identificação individual dos machos galhados, a proporção sexual e a detecção de filhotes na população. O custo das armadilhas fotográficas foi 78% menor, porém demandou um esforço de campo 20 vezes maior. Avaliamos que as armadilhas fotográficas apresentaram uma relação custo-benefício superiores em relação aos levantamentos aéreos, por ser mais informativa e barata e com uma logística mais simples. Sua aplicação abre a possibilidade para o estudo de um número maior de populações e o monitoramento contínuo e de longo prazo.

Population density of the western burrowing owl (Athene cunicularia hypugaea) in Mexican prairie dog (Cynomys mexicanus) colonies in northeastern Mexico.

BACKGROUND: The western burrowing owl (Athene cunicularia hypugaea) occurs throughout western North America in various habitats such as desert, short-grass prairie and shrub-steppe, among others, where the main threat for this species is habitat loss. Range-wide declines have prompted a need for reliable estimates of its populations in Mexico, where the size of resident and migratory populations remain unknown. RESULTS: Our objective was to estimate the abundance and density of breeding western burrowing owl populations in Mexican prairie dog (Cynomys mexicanus) colonies in two sites located within the Chihuahuan Desert ecoregion in the states of Nuevo Leon and San Luis Potosi, Mexico. Line transect surveys were conducted from February to April of 2010 and 2011. Fifty 60 ha transects were analyzed using distance sampling to estimate owl and Mexican prairie dog populations. We estimated a population of 2026 owls (95 % CI 1756-2336) in 2010 and 2015 owls (95 % CI 1573-2317) in 2011 across 50 Mexican prairie dog colonies (20,529 ha). CONCLUSIONS: The results represent the first systematic attempt to provide reliable evidence related to the size of the adult owl populations, within the largest and best preserved Mexican prairie dog colonies in Mexico.

Humpback whale Megaptera novaeangliae (Cetartiodactyla: Balaenopteridae) group sizes in line transect ship surveys: an evaluation of observer errors

Accurate estimates of group sizes through line transect sampling methods are important to correctly ascertain the abundance of animals that occur in groups. Since the average observed group size is a component of the distance sampling formula, bias in these data leads to biased abundance estimates. This study aimed to evaluate the potential errors in group size estimation during line transect ship surveys to estimate abundances of the humpback whale, Megaptera novaeangliae (Borowski 1781). In a research cruise along the Brazilian coast, an experiment to collect group size information was conducted from two different sighting platforms on the same vessel. Group sizes were recorded by primary observers at first sighting (PO1) and, in some cases, after some time (PO2). A tracker (T) was located on a higher platform to estimate the sizes of groups detected by the primary observers, but tracked one group at a time until it passed abeam. Thus, the dedicated effort to obtain multiple group counts (i.e. higher platform, more time and no responsibility for detecting new groups) was expected to provide more accurate numbers. PO2 estimates were compared with PO1 estimates, and T estimates were compared with both PO1 and PO2. Additionally, ratios between T and both PO2 (R1) and PO1 (R2), and between PO2 and PO1 (R3) were calculated. To investigate a possible improvement in abundance estimates, a correction factor (CF) was computed from the ratio of T and PO2 means. Primary observer self-correction (= 1.60, CV% = 70.3) was statistically similar to the correction for the tracker (= 1.62, CV% = 84.1). CF resulted in 1 and would not improve abundance estimates. This study supports that observers conducting line transect surveys on large whales have the potential to provide group size information that is as adequate as the correction procedure adopted.

Humpback whale Megaptera novaeangliae (Cetartiodactyla: Balaenopteridae) group sizes in line transect ship surveys: an evaluation of observer errors

Accurate estimates of group sizes through line transect sampling methods are important to correctly ascertain the abundance of animals that occur in groups. Since the average observed group size is a component of the distance sampling formula, bias in these data leads to biased abundance estimates. This study aimed to evaluate the potential errors in group size estimation during line transect ship surveys to estimate abundances of the humpback whale, Megaptera novaeangliae (Borowski 1781). In a research cruise along the Brazilian coast, an experiment to collect group size information was conducted from two different sighting platforms on the same vessel. Group sizes were recorded by primary observers at first sighting (PO1) and, in some cases, after some time (PO2). A tracker (T) was located on a higher platform to estimate the sizes of groups detected by the primary observers, but tracked one group at a time until it passed abeam. Thus, the dedicated effort to obtain multiple group counts (i.e. higher platform, more time and no responsibility for detecting new groups) was expected to provide more accurate numbers. PO2 estimates were compared with PO1 estimates, and T estimates were compared with both PO1 and PO2. Additionally, ratios between T and both PO2 (R1) and PO1 (R2), and between PO2 and PO1 (R3) were calculated. To investigate a possible improvement in abundance estimates, a correction factor (CF) was computed from the ratio of T and PO2 means. Primary observer self-correction (= 1.60, CV% = 70.3) was statistically similar to the correction for the tracker (= 1.62, CV% = 84.1). CF resulted in 1 and would not improve abundance estimates. This study supports that observers conducting line transect surveys on large whales have the potential to provide group size information that is as adequate as the correction procedure adopted.(AU)

Population density and primate conservation in the Noroeste Biosphere Reserve, Tumbes, Peru / Densidad poblacional y conservación de los primates de la Reserva de Biosfera del Noroeste, Tumbes, Perú

The Noroeste Biosphere Reserve (NBR) is home to at least 22 species of medium and large mammals including the primates Alouatta palliata aequatorialis and Cebus albifrons aequatorialis. Previous estimates of A. p. aequatorialis population density vary from 2.3-8.6 ind/km² in 1983 to 17-19 ind/km² in 2005 and 2006, respectively. While for C. a. aequatorialis there are no estimates of population density in the NBR. In order to calculate the population density estimates for both species we installed six transects in 10.5 km² within the Cerros de Amotape National Park (belonging to the NBR) from August 2012 to March 2013. Based on 112.3 km of transects we obtained a population density of 8.3 ± 3.6 ind/km² for A. p. aequatorialis. However, for the reduced number of Cebus albifrons aequatorialis sightings we were only able to calculate a group size from three to 12 individuals and an encounter rate of 0.3 ind/km. Even though A. p. aequatorialis has potentially increased in population density, it is not feasible to make comparisons with previous estimates in the same area because of the different employed methodologies and the lack of randomness in the data collection. We recommend a long-term monitoring plan, including C. a. aequatorialis which makes it a conservation priority for the NBR, this monitoring plan should include mitigation of potential threats such as illegal hunting and trapping for the pet trade.

La Reserva de Biósfera del Noroeste (RBN) alberga por lo menos 22 especies de mamíferos medianos y grandes entre las cuales se encuentran los primates Alouatta palliata aequatorialis y Cebus albifrons aequatorialis. Los estimados previos de la densidad poblacional de A. p. aequatorialis varían de 2.3‒8.6 ind/km² en 1983 a 17‒19 ind/km² en 2005 y 2006, respectivamente. Mientras que para C. a. aequatorialis no existen estimados poblacionales para la RBN. Para calcular la densidad poblacional de estas dos especies instalamos seis transectos lineales en 10.5 km² dentro del Parque Nacional Cerros de Amotape (perteneciente a la RBN) de agosto del 2012 a marzo del 2013. En base a 112.3 km de transectos se obtuvo una densidad poblacional de 8.3 ± 3.6 ind/km² para A. p. aequatorialis; sin embargo, por el reducido número de avistamientos de Cebus albifrons aequatorialis solo se pudo calcular el tamaño de grupo que varió de tres a 12 individuos y la tasa de encuentro de 0.3 ind/km. A pesar que la población del A. p. aequatorialis aparentemente ha aumentado, no es factible hacer comparaciones con los estimados anteriores debido a las diferentes metodologías empleadas y a la falta de aleatoriedad en la toma de datos. Recomendamos un plan de monitoreo a largo plazo, que incluya a C. a. aequatorialis como objeto y prioridad de conservación para la RBN, el cual debería incluir la mitigación de posibles amenazas como caza y captura para comercio de mascotas.