ABSTRACT
The bighorn sheep in Mexico is classified as at-risk by the Mexican federal government. In the state of Baja California, wild sheep can be observed throughout the length of the state from the USA-Mexico border south to the Agua de Soda mountain range. This research aimed to document the historical trend of the bighorn population based on aerial surveys conducted in 1992, 1995, 1999, 2010, and 2021, and the abundance, distribution, and structure of bighorn sheep populations in Baja California, based on an aerial survey conducted from 8-14 November 2021, covering thirteen mountain ranges. The estimated sheep population in 2021 was based on the number of individuals observed; the sightability of the animals; the area sampled; and the total area of habitat available. In 30.5 flight hours, 456 bighorn sheep were observed, with an estimated population of 1697 ± 80 individuals. The observation rate was 16 sheep sighted per hour of flight, and the ram:ewe:lamb ratio was 62:100:19. When the results of the 2021 flight were compared to the results of the previous aerial surveys, there was a large variation between the data, which was related to the lack of consistency between the sampling designs used in each study. Nevertheless, a statistical test of the results of aerial surveys conducted in the state suggest that the Baja California bighorn sheep population remained stable between 1992 and 2021. This study highlights the need to standardize wild sheep aerial surveys by defining flight paths and establishing a consistent duration of flights. On the other hand, Baja California authorities should consider modifying the current conservation strategy for bighorn sheep to increase the species' population in the state by initiating community-based wildlife conservation programs in rural communities.
ABSTRACT
Globally, six of the seven sea turtle species are threatened or endangered and as such, monitoring reproductive activity for these species is necessary for effective population recovery. Remote beaches provide a challenge to conducting these surveys, which often results in data gaps that can hamper management planning. Throughout the summer of 2022, aerial surveys were conducted over the Chandeleur Islands in the Gulf of Mexico. Turtle crawls were photographed for subsequent review by 10 expert observers. Whenever possible, ground surveys were conducted, and samples of unhatched eggs or dead hatchlings were collected. A summary of historic reports of sea turtle nesting activity at this site was also compiled. On 11 days between May 4, 2022, and July 30, 2022, photographs of 55 potential sea turtle crawls were taken. Observers identified 54 of those as being made by a sea turtle. There was high-to-moderate certainty that 16 of those crawls were nests, that 14 were made by loggerheads, and that two were made by Kemp's ridleys. Observers were least certain of species identification when surveys were conducted during rainy weather. Genetic analyses based on mitochondrial and nuclear DNA were conducted on samples from five nests and those analyses confirmed that three nests were laid by Kemp's ridleys and two were laid by loggerheads. Historic records from the Chandeleur Islands substantiate claims that the Chandeleurs have supported sea turtle nesting activity for decades; however, the consistency of this activity remains unknown. Our aerial surveys, particularly when coupled with imaging, were a useful tool for documenting nesting activity on these remote islands. Future monitoring programs at this site could benefit from a standardized aerial survey program with a seaplane so trends in nesting activity could be determined particularly as the beach undergoes restoration.
ABSTRACT
Cabo Pulmo National Park was established in 1995 and has since seen a large increase in fish biomass. An unoccupied aerial vehicle (UAV) was used to survey shallow coastal habitat in which lemon sharks (Negaprion brevirostris), bull sharks (Carcharhinus leucas) and Pacific nurse sharks (Ginglymostoma unami) were recorded. Sharks were more common in the afternoon, potentially using warmer shallow areas to behaviourally thermoregulate. This study highlights UAV surveying to be a viable tool for species identification, a limitation of previous terrestrial surveys conducted in the area.
Subject(s)
Sharks , Animals , Ecosystem , Fishes , Sand , SeafoodABSTRACT
It is well known that remote sensing is a series of procedures which detects physical characteristics of the earth surface by remotely-measuring its reflected and emitted radiation using cameras or sensors. Lately, the increasing use of unmanned aerial vehicles (UAVs) as remote sensing platforms and the development of small-size sensors have resulted in the expansion of continuous monitoring of earth surface at smaller spatial scales. For this reason, the integration of UAV- and consumer-grade cameras can be useful to acquire surface characteristics at plot or footprint scale. This dataset contains 314 aerial images covering an area of aproximately 18,800 m2 within the footprint of an Eddy covariance and meterorological station. The monitoring site was deployed at "El Soldado" estuary (27°57'14.4â³ N and 110°58'19.2â³ W) located in the southern coast of the Mexican State of Sonora. UAV flight path was programmed to flight in autonomous mode with an altitude of 30 m, a velocity of 5â¯m/s and a frontal and side overlap of 85 and 75% respectively. This dataset was created to support mapping surveys for surface classification and site description. This dataset is aimed to support researchers, stakeholders and general public interested in coastal areas, natural resources management and ecosystem conservation. Finally, this dataset could be also used for those interested in digital photogrammetry and 3D reconstruction as benchmark example to develop high resolution orthomosaics.
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.(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)
Subject(s)
Animals , Antelopes , Animal Distribution , Photograph/methods , Records , 16128 , Sex Ratio , Sampling Studies , BrazilABSTRACT
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 [...]
Subject(s)
Animals , Antelopes , Animal Distribution , 16128 , Photograph/methods , Records , Sampling Studies , Brazil , Sex RatioABSTRACT
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.
ABSTRACT
We conducted an aerial survey of the marsh deer population Blastocerus dichotomus (Illiger, 1815) in the Ilha Grande National Park and its surroundings, on the border between the states of Paraná and Mato Grosso do Sul, Brazil, during the dry season. We used the double-counting technique, resulting in a population estimate of 1079 ± 207 marsh deers in a sampled area of 1081 km², corresponding to an estimated density of 0.998 ± 0.192 ind/km². The population was mostly concentrated inside the park, but also occupied altered wetlands outside its limits. The results should be used to support population management and conservation measures at the national park and its surroundings, due to the enormous anthropogenic pressure upon the marsh deer population in the region.
Nós conduzimos um levantamento populacional aéreo do cervo-do-pantanal, Blastocerus dichotomus (Illiger, 1815), no Parque Nacional de Ilha Grande e seu entorno, entre os estados do Paraná e Mato Grosso do Sul, Brasil, na estação seca. Utilizamos a técnica da contagem dupla, e a população foi estimada em 1.079 ± 207 cervos em uma área amostral de 1.081 km², corresponde a uma densidade de 0,998 ± 0,192 ind/km². A população mostrou-se mais concentrada no interior do parque, ocupando também várzeas alteradas fora dos limites do parque. Estes resultados devem subsidiar medidas de manejo e conservação da população no parque nacional e seu entorno, devido à enorme pressão antrópica sobre a população de cervos na região.
ABSTRACT
We conducted an aerial survey of the marsh deer population Blastocerus dichotomus (Illiger, 1815) in the Ilha Grande National Park and its surroundings, on the border between the states of Paraná and Mato Grosso do Sul, Brazil, during the dry season. We used the double-counting technique, resulting in a population estimate of 1079 ± 207 marsh deers in a sampled area of 1081 km², corresponding to an estimated density of 0.998 ± 0.192 ind/km². The population was mostly concentrated inside the park, but also occupied altered wetlands outside its limits. The results should be used to support population management and conservation measures at the national park and its surroundings, due to the enormous anthropogenic pressure upon the marsh deer population in the region.
Nós conduzimos um levantamento populacional aéreo do cervo-do-pantanal, Blastocerus dichotomus (Illiger, 1815), no Parque Nacional de Ilha Grande e seu entorno, entre os estados do Paraná e Mato Grosso do Sul, Brasil, na estação seca. Utilizamos a técnica da contagem dupla, e a população foi estimada em 1.079 ± 207 cervos em uma área amostral de 1.081 km², corresponde a uma densidade de 0,998 ± 0,192 ind/km². A população mostrou-se mais concentrada no interior do parque, ocupando também várzeas alteradas fora dos limites do parque. Estes resultados devem subsidiar medidas de manejo e conservação da população no parque nacional e seu entorno, devido à enorme pressão antrópica sobre a população de cervos na região.