Interactions between species and individuals can determine their survival in the wild. Most of th... more Interactions between species and individuals can determine their survival in the wild. Most of the time these relationships are difficult to study in situ by direct observation. However, technology can help collect these data with minimal impact on animals’ behaviour. Egg stage is certainly the most vulnerable life stage in crocodilians, but few studies have focused on animal species visiting crocodilian nests and associated egg predation. Herein, we use camera-traps in four Mexican states (Chiapas, Oaxaca, Jalisco, Tabasco) to determine vertebrate species and egg predators associated with wild nests of Caiman crocodilus chiapasius, Crocodylus acutus and Crocodylus moreletii. We recorded 72 species of vertebrates at nesting sites and obtained the first photographic evidence of crocodilian egg predation by Caracara cheriway, Cuniculus paca, Didelphis virginiana and Procyon lotor. We also identified commensalism, cooperation, and predation as types of interactions within observed nest...
Oil palm plantations are expanding in Mexico, primarily in areas already dominated by induced gra... more Oil palm plantations are expanding in Mexico, primarily in areas already dominated by induced grasslands and other crops. There is a large body of information on the reduction of biodiversity in oil palm plantations compared to conserved forests. However, only a few studies have been performed in already anthropized matrices where almost all the natural vegetation has been replaced. To determine the effect of oil palm plantations located in an anthropized landscape on amphibian biodiversity, we obtained amphibian species richness and abundance using 48 transects distributed among seven oil palm plantation estates situated in the Gulf of Mexico lowlands in southeastern Mexico and compared with the observed amphibian biodiversity obtained from 15 previously published amphibian surveys on the area. Our survey in the oil palm plantations resulted in 1,977 individuals belonging to 15 species from seven anuran families. Although anuran diversity varies among the studied plantation estates, few significant differences were detected. We observed that the species richness in oil palm plantations represents 41.7% of the species detected in the region. However, we observed that more than half of the species (21 of 36) that have been detected in the region appeared in less than 30% of the sites studied, and the 15 remaining species that are more frequently detected in the area, 12 (80%) are present in oil palm plantations. Our study region has a long history of agricultural use and is already heavily fragmented. Thus, the remarkable similarity observed between the anuran species found in oil palm plantations and the most frequent amphibian species in the Gulf of Mexico lowlands can be explained by an already depauperate landscape dominated by species that are disturbance-tolerant or benefited from habitat modifications. Oil palm plantations in the region will expand in the future. Our results show that if the expansion continues to replace induced grasslands or other crops will have a reduced impact on the anuran biodiversity in this region. However, this expansion should preserve the remanent secondary growth forest patches distributed along the landscape to maintain the regional anuran diversity.
Background and Research Aims The Urías Coastal Lagoon (UCL) is a heavily modified and polluted la... more Background and Research Aims The Urías Coastal Lagoon (UCL) is a heavily modified and polluted lagoon near Mazatlán, in northwestern Mexico. Once abundant in the UCL, the American crocodile ( Crocodylus acutus) is now rarely seen in the area. A healthy population of apex predators is essential to maintain the trophic balance of ecosystems. Our research aim was to lay the groundwork for studies of American crocodile population ecology in the UCL. Methods Traditional boat surveys (day and night) of crocodiles were undertaken in the UCL in May-July 2022. Two exploratory aerial (∼ 30 m altitude) surveys of a small wetland located close to a habitational complex in the vicinity of the UCL were performed in June and December 2022, using a commercial Unmanned Aerial Vehicle (UAV). We used images obtained with the UAV to estimate the size of the crocodiles detected in the wetland. Results This study confirms the presence of American crocodiles in the UCL and presents the first information o...
Studies on Neotropical Fauna and Environment, 2024
Crocodilians injuries are indicators of their health and social interactions. We analyzed the pre... more Crocodilians injuries are indicators of their health and social interactions. We analyzed the prevalence and distribution of injuries in spectacled caiman (Caiman crocodilus chiapasius) from the Biosphere Reserve of La Encrucijada (BRLE) in relation to the habitat, size, and sex of individuals. We collected data on injuries in caimans captured during nocturnal surveys (2014–2022) in the estuary and swamps of the BRLE. We determined the sex of each caiman, measured their snout–vent length, and registered the type of injury and body region where injuries were detected. From all records, 102 of 301 caimans (33.9%) presented injuries and they were more likely to be injured in the estuary than in the swamps, probably due to the presence of a larger sympatric crocodile species in the estuary (Crocodylus acutus). Sex had no effect on the proportion of injured individuals, but larger caimans have a higher probability of being injured than smaller ones, explained by an ontogenetic change in the individuals’ behaviors. Habitat, sex, and size class of individuals do not influence the number of injuries on different body regions. The tail was the most injured body region (17.6% of individuals), followed by the abdomen (13.0%), back (12.6%), head (9.6%), and extremities (4.0%).
Understanding the demographic structure is vital for wildlife research and conservation.
For croc... more Understanding the demographic structure is vital for wildlife research and conservation. For crocodylians, accurately estimating total length and demographic class usually necessitates close observation or capture, often of partially immersed individuals, leading to potential imprecision and risk. Drone technology offers a bias-free, safer alternative for classification. We evaluated the effectiveness of drone photos combined with head length allometric relationships to estimate total length, and propose a standardized method for drone-based crocodylian demographic classification. We evaluated error sources related to drone flight parameters using standardized targets. An allometric framework correlating head to total length for 17 crocodylian species was developed, incorporating confidence intervals to account for imprecision sources (e.g., allometric accuracy, head inclination, observer bias, terrain variability). This method was applied to wild crocodylians through drone photography. Target measurements from drone imagery, across various resolutions and sizes, were consistent with their actual dimensions. Terrain effects were less impactful than Ground- Sample Distance (GSD) errors from photogrammetric software. The allometric framework predicted lengths within ≃11–18% accuracy across species, with natural allometric variation among individuals explaining much of this range. Compared to traditional methods that can be subjective and risky, our drone-based approach is objective, efficient, fast, cheap, non-invasive, and safe. Nonetheless, further refinements are needed to extend survey times and better include smaller size classes.
The herpetofauna of the insular systems of Mexico is composed of 226 species, of which 14 are anu... more The herpetofauna of the insular systems of Mexico is composed of 226 species, of which 14 are anurans, two are salamanders, and 210 are reptiles, comprised of two crocodilians, 195 squamates, and 13 turtles. Although the surface of the Mexican islands is only 0.26% of the Mexican territorial extension, these 226 species constitute 16.1% of Mexico’s documented herpetofauna of 1405 species. We classified the Mexican islands into five physiographic regions: the islands of Pacific Baja California; the islands of the Gulf of California; the islands of the Tropical Pacific; the islands of the Gulf of Mexico; and the islands of the Mexican Caribbean. The highest species richness among these regions is in the Gulf of California, with 108 species, and the lowest richness is 40 for the islands of the Pacific Baja California and 46 for those of the Gulf of Mexico. We identified introduced species, risk of wildfires, climate change, and urban/tourist development as the main environmental threat...
Background and Research Aims: The Urías Coastal Lagoon (UCL) is a heavily modified and polluted l... more Background and Research Aims: The Urías Coastal Lagoon (UCL) is a heavily modified and polluted lagoon near Mazatlán, in northwestern Mexico. Once abundant in the UCL, the American crocodile (Crocodylus acutus) is now rarely seen in the area. A healthy population of apex predators is essential to maintain the trophic balance of ecosystems. Our research aim was to lay the groundwork for studies of American crocodile population ecology in the UCL. Methods: Traditional boat surveys (day and night) of crocodiles were undertaken in the UCL in May-July 2022. Two exploratory aerial (∼ 30 m altitude) surveys of a small wetland located close to a habitational complex in the vicinity of the UCL were performed in June and December 2022, using a commercial Unmanned Aerial Vehicle (UAV). We used images obtained with the UAV to estimate the size of the crocodiles detected in the wetland. Results: This study confirms the presence of American crocodiles in the UCL and presents the first information on individuals of this species for this area. Aerial surveys revealed the presence of 17 individuals in the wetland; the mean size of nine of those individuals was 183.3 ± 60 cm (range: 130-310 cm). Two yearlings (∼37 cm length), possibly born in June 2022, were captured in the same wetland in September 2022. We also surveyed 50.7 km of UCL coastline by boat, but no crocodiles were sighted. Conclusion: The crocodiles seem to avoid the human-impacted UCL and likely use the less impacted surrounding wetlands as a refuge area, which they also use to reproduce. The presence of both yearlings and adults is a good sign for the survival of this vulnerable population. Implications for Conservation: We believe that the surveyed wetland should be closely monitored for conservation purposes because it might be one of the last crocodile breeding refuges in the heavily modified and polluted coastal environment of the UCL. We summarize our results with a series of recommendations for local and federal authorities. These recommendations would likely help the conservation of the American crocodile population in the UCL.
Background and Research Aims: The Urías Coastal Lagoon (UCL) is a heavily modified and polluted l... more Background and Research Aims: The Urías Coastal Lagoon (UCL) is a heavily modified and polluted lagoon near Mazatlán, in northwestern Mexico. Once abundant in the UCL, the American crocodile (Crocodylus acutus) is now rarely seen in the area. A healthy population of apex predators is essential to maintain the trophic balance of ecosystems. Our research aim was to lay the groundwork for studies of American crocodile population ecology in the UCL. Methods: Traditional boat surveys (day and night) of crocodiles were undertaken in the UCL in May-July 2022. Two exploratory aerial (∼ 30 m altitude) surveys of a small wetland located close to a habitational complex in the vicinity of the UCL were performed in June and December 2022, using a commercial Unmanned Aerial Vehicle (UAV). We used images obtained with the UAV to estimate the size of the crocodiles detected in the wetland. Results: This study confirms the presence of American crocodiles in the UCL and presents the first information on individuals of this species for this area. Aerial surveys revealed the presence of 17 individuals in the wetland; the mean size of nine of those individuals was 183.3 ± 60 cm (range: 130-310 cm). Two yearlings (∼37 cm length), possibly born in June 2022, were captured in the same wetland in September 2022. We also surveyed 50.7 km of UCL coastline by boat, but no crocodiles were sighted. Conclusion: The crocodiles seem to avoid the human-impacted UCL and likely use the less impacted surrounding wetlands as a refuge area, which they also use to reproduce. The presence of both yearlings and adults is a good sign for the survival of this vulnerable population. Implications for Conservation: We believe that the surveyed wetland should be closely monitored for conservation purposes because it might be one of the last crocodile breeding refuges in the heavily modified and polluted coastal environment of the UCL. We summarize our results with a series of recommendations for local and federal authorities. These recommendations would likely help the conservation of the American crocodile population in the UCL.
The herpetofauna of the insular systems of Mexico is composed of 226 species, of which 14 are anu... more The herpetofauna of the insular systems of Mexico is composed of 226 species, of which 14 are anurans, two are salamanders, and 210 are reptiles, comprised of two crocodilians, 195 squamates, and 13 turtles. Although the surface of the Mexican islands is only 0.26% of the Mexican territorial extension, these 226 species constitute 16.1% of Mexico’s documented herpetofauna of 1405 species. We classified the Mexican islands into five physiographic regions: the islands of Pacific Baja California; the islands of the Gulf of California; the islands of the Tropical Pacific; the islands of the Gulf of Mexico; and the islands of the Mexican Caribbean. The highest species richness among these regions is in the Gulf of California, with 108 species, and the lowest richness is 40 for the islands of the Pacific Baja California and 46 for those of the Gulf of Mexico. We identified introduced species, risk of wildfires, climate change, and urban/tourist development as the main environmental threats impinging on these species. In addition, we assessed the conservation status of the native species by comparing the SEMARNAT (NOM-059), IUCN Red List, and the Environmental Vulnerability Score (EVS) systems. The comparison of these systems showed that the NOM-059 and the IUCN systems seriously underestimate the degree of threat for insular endemics, being particularly concerning for those insular species that are known only from their respective type localities. The EVS system proved to be practical and indicated that 94 species have a high vulnerability status, 62 a medium status, and 56 a low status. The Relative Herpetofaunal Priority system, which contrasts the number of endemic and threatened species among different physiographic areas, indicates that the regions with the highest priority are the Islands of the Gulf of California, followed by the islands of the Tropical Pacific. Finally, we discussed the completeness of the Mexican Natural Protected Areas on the insular systems of the country; the result is outstanding since Mexico is already close to achieving the goal of having all their islands under some degree of federal protection.
This study apports new information on the diversity of amphibians and reptiles in a freshwater we... more This study apports new information on the diversity of amphibians and reptiles in a freshwater wetland of Tabasco. From January to December 2014, monthly samplings were conducted in the Chaschoc lagoon wetlands to establish a checklist of amphibians and reptiles for this site and to detect potential threats to their conservation. Diurnal and nocturnal surveys were conducted in terrestrial habitats, while surveys were conducted in water bodies for turtles and crocodiles. Fifty-five species were detected (12 amphibians, and 43 reptiles), representing 32.4% of the species recorded for Tabasco. Species accumulation models resulted in percentages of inventory completeness above 92 %. Most of the species do not appear in IUCN Red List of threatened species, appendices of CITES, or the list of threatened species of the Official Mexican Norm NOM-59-SEMARNAT-2010. Main threats detected for the herpetofauna were cattle ranching, illegal hunting and collecting, destruction, fragmentation and p...
Interspecific interactions between vertebrates of different groups are common but also complex an... more Interspecific interactions between vertebrates of different groups are common but also complex and of great importance for community structure. In particular, predation, considered a trophic interaction, plays a significant role in food webs structure and selective effects on prey in natural ecosystems. In this paper we provide new information on the trophic relationship between birds and herpetofauna (reptiles and amphibians) in the complex and biodiverse Usumacinta river basin, through 10 observations recorded between 2012 and 2021. The observations show interactions for feeding purposes of eight bird species, including herons (Tigrisoma mexicanum), jays (Psilorhinus morio), raptors (Caracara cheriway, Pseudastur albicollis, Harpagus bidentatus, Buteo plagiatus), puffbirds (Malacoptila panamensis), and ducks (Dendrocygna autumnalis), with snakes (Coniophanes quinquevittatus), turtles (Chelydra rossignonii, Trachemys venusta), lizards (Iguana iguana, Sceloporus serrifer), crocodiles (Crocodylus moreletii), and frogs (Smilisca baudinii).
Figure 2. Climatic diagram from the meteorological station of Mahahual, with periods of courtship... more Figure 2. Climatic diagram from the meteorological station of Mahahual, with periods of courtship and mating (thin line), laying (dashed line), and hatching (thick line) of American crocodiles in Banco Chinchorro.
Interactions between species and individuals can determine their survival in the wild. Most of th... more Interactions between species and individuals can determine their survival in the wild. Most of the time these relationships are difficult to study in situ by direct observation. However, technology can help collect these data with minimal impact on animals’ behaviour. Egg stage is certainly the most vulnerable life stage in crocodilians, but few studies have focused on animal species visiting crocodilian nests and associated egg predation. Herein, we use camera-traps in four Mexican states (Chiapas, Oaxaca, Jalisco, Tabasco) to determine vertebrate species and egg predators associated with wild nests of Caiman crocodilus chiapasius, Crocodylus acutus and Crocodylus moreletii. We recorded 72 species of vertebrates at nesting sites and obtained the first photographic evidence of crocodilian egg predation by Caracara cheriway, Cuniculus paca, Didelphis virginiana and Procyon lotor. We also identified commensalism, cooperation, and predation as types of interactions within observed nest...
Oil palm plantations are expanding in Mexico, primarily in areas already dominated by induced gra... more Oil palm plantations are expanding in Mexico, primarily in areas already dominated by induced grasslands and other crops. There is a large body of information on the reduction of biodiversity in oil palm plantations compared to conserved forests. However, only a few studies have been performed in already anthropized matrices where almost all the natural vegetation has been replaced. To determine the effect of oil palm plantations located in an anthropized landscape on amphibian biodiversity, we obtained amphibian species richness and abundance using 48 transects distributed among seven oil palm plantation estates situated in the Gulf of Mexico lowlands in southeastern Mexico and compared with the observed amphibian biodiversity obtained from 15 previously published amphibian surveys on the area. Our survey in the oil palm plantations resulted in 1,977 individuals belonging to 15 species from seven anuran families. Although anuran diversity varies among the studied plantation estates, few significant differences were detected. We observed that the species richness in oil palm plantations represents 41.7% of the species detected in the region. However, we observed that more than half of the species (21 of 36) that have been detected in the region appeared in less than 30% of the sites studied, and the 15 remaining species that are more frequently detected in the area, 12 (80%) are present in oil palm plantations. Our study region has a long history of agricultural use and is already heavily fragmented. Thus, the remarkable similarity observed between the anuran species found in oil palm plantations and the most frequent amphibian species in the Gulf of Mexico lowlands can be explained by an already depauperate landscape dominated by species that are disturbance-tolerant or benefited from habitat modifications. Oil palm plantations in the region will expand in the future. Our results show that if the expansion continues to replace induced grasslands or other crops will have a reduced impact on the anuran biodiversity in this region. However, this expansion should preserve the remanent secondary growth forest patches distributed along the landscape to maintain the regional anuran diversity.
Background and Research Aims The Urías Coastal Lagoon (UCL) is a heavily modified and polluted la... more Background and Research Aims The Urías Coastal Lagoon (UCL) is a heavily modified and polluted lagoon near Mazatlán, in northwestern Mexico. Once abundant in the UCL, the American crocodile ( Crocodylus acutus) is now rarely seen in the area. A healthy population of apex predators is essential to maintain the trophic balance of ecosystems. Our research aim was to lay the groundwork for studies of American crocodile population ecology in the UCL. Methods Traditional boat surveys (day and night) of crocodiles were undertaken in the UCL in May-July 2022. Two exploratory aerial (∼ 30 m altitude) surveys of a small wetland located close to a habitational complex in the vicinity of the UCL were performed in June and December 2022, using a commercial Unmanned Aerial Vehicle (UAV). We used images obtained with the UAV to estimate the size of the crocodiles detected in the wetland. Results This study confirms the presence of American crocodiles in the UCL and presents the first information o...
Studies on Neotropical Fauna and Environment, 2024
Crocodilians injuries are indicators of their health and social interactions. We analyzed the pre... more Crocodilians injuries are indicators of their health and social interactions. We analyzed the prevalence and distribution of injuries in spectacled caiman (Caiman crocodilus chiapasius) from the Biosphere Reserve of La Encrucijada (BRLE) in relation to the habitat, size, and sex of individuals. We collected data on injuries in caimans captured during nocturnal surveys (2014–2022) in the estuary and swamps of the BRLE. We determined the sex of each caiman, measured their snout–vent length, and registered the type of injury and body region where injuries were detected. From all records, 102 of 301 caimans (33.9%) presented injuries and they were more likely to be injured in the estuary than in the swamps, probably due to the presence of a larger sympatric crocodile species in the estuary (Crocodylus acutus). Sex had no effect on the proportion of injured individuals, but larger caimans have a higher probability of being injured than smaller ones, explained by an ontogenetic change in the individuals’ behaviors. Habitat, sex, and size class of individuals do not influence the number of injuries on different body regions. The tail was the most injured body region (17.6% of individuals), followed by the abdomen (13.0%), back (12.6%), head (9.6%), and extremities (4.0%).
Understanding the demographic structure is vital for wildlife research and conservation.
For croc... more Understanding the demographic structure is vital for wildlife research and conservation. For crocodylians, accurately estimating total length and demographic class usually necessitates close observation or capture, often of partially immersed individuals, leading to potential imprecision and risk. Drone technology offers a bias-free, safer alternative for classification. We evaluated the effectiveness of drone photos combined with head length allometric relationships to estimate total length, and propose a standardized method for drone-based crocodylian demographic classification. We evaluated error sources related to drone flight parameters using standardized targets. An allometric framework correlating head to total length for 17 crocodylian species was developed, incorporating confidence intervals to account for imprecision sources (e.g., allometric accuracy, head inclination, observer bias, terrain variability). This method was applied to wild crocodylians through drone photography. Target measurements from drone imagery, across various resolutions and sizes, were consistent with their actual dimensions. Terrain effects were less impactful than Ground- Sample Distance (GSD) errors from photogrammetric software. The allometric framework predicted lengths within ≃11–18% accuracy across species, with natural allometric variation among individuals explaining much of this range. Compared to traditional methods that can be subjective and risky, our drone-based approach is objective, efficient, fast, cheap, non-invasive, and safe. Nonetheless, further refinements are needed to extend survey times and better include smaller size classes.
The herpetofauna of the insular systems of Mexico is composed of 226 species, of which 14 are anu... more The herpetofauna of the insular systems of Mexico is composed of 226 species, of which 14 are anurans, two are salamanders, and 210 are reptiles, comprised of two crocodilians, 195 squamates, and 13 turtles. Although the surface of the Mexican islands is only 0.26% of the Mexican territorial extension, these 226 species constitute 16.1% of Mexico’s documented herpetofauna of 1405 species. We classified the Mexican islands into five physiographic regions: the islands of Pacific Baja California; the islands of the Gulf of California; the islands of the Tropical Pacific; the islands of the Gulf of Mexico; and the islands of the Mexican Caribbean. The highest species richness among these regions is in the Gulf of California, with 108 species, and the lowest richness is 40 for the islands of the Pacific Baja California and 46 for those of the Gulf of Mexico. We identified introduced species, risk of wildfires, climate change, and urban/tourist development as the main environmental threat...
Background and Research Aims: The Urías Coastal Lagoon (UCL) is a heavily modified and polluted l... more Background and Research Aims: The Urías Coastal Lagoon (UCL) is a heavily modified and polluted lagoon near Mazatlán, in northwestern Mexico. Once abundant in the UCL, the American crocodile (Crocodylus acutus) is now rarely seen in the area. A healthy population of apex predators is essential to maintain the trophic balance of ecosystems. Our research aim was to lay the groundwork for studies of American crocodile population ecology in the UCL. Methods: Traditional boat surveys (day and night) of crocodiles were undertaken in the UCL in May-July 2022. Two exploratory aerial (∼ 30 m altitude) surveys of a small wetland located close to a habitational complex in the vicinity of the UCL were performed in June and December 2022, using a commercial Unmanned Aerial Vehicle (UAV). We used images obtained with the UAV to estimate the size of the crocodiles detected in the wetland. Results: This study confirms the presence of American crocodiles in the UCL and presents the first information on individuals of this species for this area. Aerial surveys revealed the presence of 17 individuals in the wetland; the mean size of nine of those individuals was 183.3 ± 60 cm (range: 130-310 cm). Two yearlings (∼37 cm length), possibly born in June 2022, were captured in the same wetland in September 2022. We also surveyed 50.7 km of UCL coastline by boat, but no crocodiles were sighted. Conclusion: The crocodiles seem to avoid the human-impacted UCL and likely use the less impacted surrounding wetlands as a refuge area, which they also use to reproduce. The presence of both yearlings and adults is a good sign for the survival of this vulnerable population. Implications for Conservation: We believe that the surveyed wetland should be closely monitored for conservation purposes because it might be one of the last crocodile breeding refuges in the heavily modified and polluted coastal environment of the UCL. We summarize our results with a series of recommendations for local and federal authorities. These recommendations would likely help the conservation of the American crocodile population in the UCL.
Background and Research Aims: The Urías Coastal Lagoon (UCL) is a heavily modified and polluted l... more Background and Research Aims: The Urías Coastal Lagoon (UCL) is a heavily modified and polluted lagoon near Mazatlán, in northwestern Mexico. Once abundant in the UCL, the American crocodile (Crocodylus acutus) is now rarely seen in the area. A healthy population of apex predators is essential to maintain the trophic balance of ecosystems. Our research aim was to lay the groundwork for studies of American crocodile population ecology in the UCL. Methods: Traditional boat surveys (day and night) of crocodiles were undertaken in the UCL in May-July 2022. Two exploratory aerial (∼ 30 m altitude) surveys of a small wetland located close to a habitational complex in the vicinity of the UCL were performed in June and December 2022, using a commercial Unmanned Aerial Vehicle (UAV). We used images obtained with the UAV to estimate the size of the crocodiles detected in the wetland. Results: This study confirms the presence of American crocodiles in the UCL and presents the first information on individuals of this species for this area. Aerial surveys revealed the presence of 17 individuals in the wetland; the mean size of nine of those individuals was 183.3 ± 60 cm (range: 130-310 cm). Two yearlings (∼37 cm length), possibly born in June 2022, were captured in the same wetland in September 2022. We also surveyed 50.7 km of UCL coastline by boat, but no crocodiles were sighted. Conclusion: The crocodiles seem to avoid the human-impacted UCL and likely use the less impacted surrounding wetlands as a refuge area, which they also use to reproduce. The presence of both yearlings and adults is a good sign for the survival of this vulnerable population. Implications for Conservation: We believe that the surveyed wetland should be closely monitored for conservation purposes because it might be one of the last crocodile breeding refuges in the heavily modified and polluted coastal environment of the UCL. We summarize our results with a series of recommendations for local and federal authorities. These recommendations would likely help the conservation of the American crocodile population in the UCL.
The herpetofauna of the insular systems of Mexico is composed of 226 species, of which 14 are anu... more The herpetofauna of the insular systems of Mexico is composed of 226 species, of which 14 are anurans, two are salamanders, and 210 are reptiles, comprised of two crocodilians, 195 squamates, and 13 turtles. Although the surface of the Mexican islands is only 0.26% of the Mexican territorial extension, these 226 species constitute 16.1% of Mexico’s documented herpetofauna of 1405 species. We classified the Mexican islands into five physiographic regions: the islands of Pacific Baja California; the islands of the Gulf of California; the islands of the Tropical Pacific; the islands of the Gulf of Mexico; and the islands of the Mexican Caribbean. The highest species richness among these regions is in the Gulf of California, with 108 species, and the lowest richness is 40 for the islands of the Pacific Baja California and 46 for those of the Gulf of Mexico. We identified introduced species, risk of wildfires, climate change, and urban/tourist development as the main environmental threats impinging on these species. In addition, we assessed the conservation status of the native species by comparing the SEMARNAT (NOM-059), IUCN Red List, and the Environmental Vulnerability Score (EVS) systems. The comparison of these systems showed that the NOM-059 and the IUCN systems seriously underestimate the degree of threat for insular endemics, being particularly concerning for those insular species that are known only from their respective type localities. The EVS system proved to be practical and indicated that 94 species have a high vulnerability status, 62 a medium status, and 56 a low status. The Relative Herpetofaunal Priority system, which contrasts the number of endemic and threatened species among different physiographic areas, indicates that the regions with the highest priority are the Islands of the Gulf of California, followed by the islands of the Tropical Pacific. Finally, we discussed the completeness of the Mexican Natural Protected Areas on the insular systems of the country; the result is outstanding since Mexico is already close to achieving the goal of having all their islands under some degree of federal protection.
This study apports new information on the diversity of amphibians and reptiles in a freshwater we... more This study apports new information on the diversity of amphibians and reptiles in a freshwater wetland of Tabasco. From January to December 2014, monthly samplings were conducted in the Chaschoc lagoon wetlands to establish a checklist of amphibians and reptiles for this site and to detect potential threats to their conservation. Diurnal and nocturnal surveys were conducted in terrestrial habitats, while surveys were conducted in water bodies for turtles and crocodiles. Fifty-five species were detected (12 amphibians, and 43 reptiles), representing 32.4% of the species recorded for Tabasco. Species accumulation models resulted in percentages of inventory completeness above 92 %. Most of the species do not appear in IUCN Red List of threatened species, appendices of CITES, or the list of threatened species of the Official Mexican Norm NOM-59-SEMARNAT-2010. Main threats detected for the herpetofauna were cattle ranching, illegal hunting and collecting, destruction, fragmentation and p...
Interspecific interactions between vertebrates of different groups are common but also complex an... more Interspecific interactions between vertebrates of different groups are common but also complex and of great importance for community structure. In particular, predation, considered a trophic interaction, plays a significant role in food webs structure and selective effects on prey in natural ecosystems. In this paper we provide new information on the trophic relationship between birds and herpetofauna (reptiles and amphibians) in the complex and biodiverse Usumacinta river basin, through 10 observations recorded between 2012 and 2021. The observations show interactions for feeding purposes of eight bird species, including herons (Tigrisoma mexicanum), jays (Psilorhinus morio), raptors (Caracara cheriway, Pseudastur albicollis, Harpagus bidentatus, Buteo plagiatus), puffbirds (Malacoptila panamensis), and ducks (Dendrocygna autumnalis), with snakes (Coniophanes quinquevittatus), turtles (Chelydra rossignonii, Trachemys venusta), lizards (Iguana iguana, Sceloporus serrifer), crocodiles (Crocodylus moreletii), and frogs (Smilisca baudinii).
Figure 2. Climatic diagram from the meteorological station of Mahahual, with periods of courtship... more Figure 2. Climatic diagram from the meteorological station of Mahahual, with periods of courtship and mating (thin line), laying (dashed line), and hatching (thick line) of American crocodiles in Banco Chinchorro.
Les sédiments de l’Usumacinta, que les habitants appellent « sable », « cailloux » ou « pierres »... more Les sédiments de l’Usumacinta, que les habitants appellent « sable », « cailloux » ou « pierres », sont composés d’argile, de limon, de boue et de gravier. Essentiels à l’écosystème fluvial, ils abritent une vie secrète et participent à la dynamique du fleuve. Ces sédiments ont été extraits et travaillés depuis des temps immémoriaux pour la production de poteries, l’amélioration des sols ou comme matériau de construction. Les sociétés se sont développées et se sont nourries grâce aux sédiments, mais avec l’expansion des activités humaines et la transformation des écosystèmes, la production, le transport et l’accumulation des sédiments ont été modifiés. Ces processus sont pourtant fondamentaux pour l’ensemble du bassin versant de l’Usumacinta. Cette publication propose d’expliquer en douze questions la nature et l’importance des sédiments de l’Usumacinta : à quoi servent-ils, quel est leur rôle dans les écosystèmes, sont-ils contaminés, quels usages ont-ils eu au fil du temps, comment peut-on les valoriser ? Les réponses, rédigées par des scientifiques, contribuent à la connaissance du fleuve et à la construction d’une relation durable avec les êtres humains qui vivent sur ses rives. Ces enjeux, exposés à travers l’exemple de l’Usumacinta, peuvent être transposés à tout autre grand fleuve. Cette publication s’inscrit dans le cadre d’une étroite collaboration scientifique entre des chercheurs mexicains et français, entre 2018 et 2022 : le projet VAL-USES « De l’usage traditionnel à la valorisation intégrée des sédiments dans le bassin du fleuve Usumacinta ». Ce projet interdisciplinaire a été approuvé et financé par l’Agence nationale de la recherche française (ANR-17-CE03-0012-01) et le Conseil national de la science et de la technologie du Mexique (FONCICYT-290792).
Los sedimentos de la cuenca del Usumacinta son compuestos de arcilla, limo, barro y grava, esenci... more Los sedimentos de la cuenca del Usumacinta son compuestos de arcilla, limo, barro y grava, esenciales por albergar una vida secreta y participar en la dinámica de este ecosistema fluvial. Los lugareños los llaman “arena”, “guijarros” o “piedras”, y han fungido como recursos desde tiempos inmemoriales para la producción de cerámica, la mejora del suelo o como material de construcción. Las sociedades se han expandido y alimentado gracias a ellos, pero con el crecimiento urbano y la transformación de los ecosistemas, hemos alterado sus dinámicas de generación, transporte y acumulación; ni más ni menos que todo aquello que resulta fundamental para la vida de un territorio conformado por una cuenca y un río compartido por Tabasco, Chiapas y el altiplano guatemalteco. Con esta publicación buscamos explicar en doce preguntas la naturaleza e importancia de los sedimentos del Usumacinta: ¿para qué se utilizan actualmente?, ¿qué usos han tenido a lo largo del tiempo?, ¿cómo pueden aprovecharse? ¿están contaminados? Nuestras respuestas buscan contribuir a la construcción de una relación sostenible entre el Usumacinta y los seres humanos que viven en sus riberas. Con este ejemplo bien podría abordarse la misma problemática respecto a cualquier otra cuenca. Esta publicación se realizó en el marco de una estrecha colaboración científica con la participación de investigadores mexicanos y franceses que, iniciada en 2018, concluye en 2022: el proyecto VAL-USES “Desde el aprovechamiento tradicional hacia la valorización integral de los sedimentos en la cuenca del río Usumacinta”, un proyecto interdisciplinario aprobado y financiado por la Agencia Nacional de Investigación en Francia y el Consejo Nacional de Ciencia y Tecnología en México.
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Papers by Pierre Charruau
of information on the reduction of biodiversity in oil palm plantations compared to conserved forests. However, only a few studies have been performed in already anthropized matrices where almost all the natural vegetation has been replaced. To determine the effect of oil palm plantations located in an anthropized landscape on amphibian biodiversity, we obtained amphibian species richness and abundance using 48 transects distributed among seven oil palm plantation estates situated in the Gulf of Mexico lowlands in southeastern Mexico and compared with the observed amphibian biodiversity obtained from 15 previously published amphibian surveys on the area. Our survey in the oil palm plantations resulted in 1,977 individuals belonging to 15 species from seven anuran families. Although anuran diversity varies among the studied plantation estates, few significant differences were detected. We observed that the species richness in oil palm plantations represents 41.7% of the species detected in the region. However, we observed that more than half of the species (21 of 36) that have been detected in the region appeared in less than 30% of the sites studied, and the 15 remaining species that are more frequently detected in the area, 12 (80%) are present in oil palm plantations. Our study region has a long history of agricultural use and is already heavily fragmented. Thus, the remarkable similarity observed between the anuran species found in oil palm plantations and the most frequent amphibian species in the Gulf of Mexico lowlands can be explained by an already depauperate landscape dominated by species that are disturbance-tolerant or benefited from habitat modifications. Oil palm plantations in the region will expand in the future. Our results show that if the expansion continues to replace induced grasslands or other crops will have a reduced impact on the anuran biodiversity in this region. However, this expansion should preserve the remanent secondary growth forest patches distributed along the landscape to maintain the regional anuran diversity.
collected data on injuries in caimans captured during nocturnal surveys (2014–2022) in the estuary and swamps of the BRLE. We determined the sex of each caiman, measured their snout–vent length, and registered the type of injury and body region where injuries were detected. From all records, 102 of 301 caimans (33.9%) presented injuries and they were more likely to be injured in the estuary than in the swamps, probably due to the presence of a larger sympatric crocodile species in the estuary (Crocodylus acutus). Sex had no effect on the proportion of injured individuals, but larger caimans have a higher probability of being injured than smaller ones, explained by
an ontogenetic change in the individuals’ behaviors. Habitat, sex, and size class of individuals do not influence the number of injuries on different body regions. The tail was the most injured body region (17.6% of individuals), followed by the abdomen (13.0%), back (12.6%), head (9.6%), and extremities (4.0%).
For crocodylians, accurately estimating total length and demographic class usually necessitates close
observation or capture, often of partially immersed individuals, leading to potential imprecision
and risk. Drone technology offers a bias-free, safer alternative for classification. We evaluated the effectiveness of drone photos combined with head length allometric relationships to estimate total
length, and propose a standardized method for drone-based crocodylian demographic classification.
We evaluated error sources related to drone flight parameters using standardized targets. An
allometric framework correlating head to total length for 17 crocodylian species was developed,
incorporating confidence intervals to account for imprecision sources (e.g., allometric accuracy, head
inclination, observer bias, terrain variability). This method was applied to wild crocodylians through
drone photography. Target measurements from drone imagery, across various resolutions and sizes,
were consistent with their actual dimensions. Terrain effects were less impactful than Ground-
Sample Distance (GSD) errors from photogrammetric software. The allometric framework predicted
lengths within ≃11–18% accuracy across species, with natural allometric variation among individuals
explaining much of this range. Compared to traditional methods that can be subjective and risky, our
drone-based approach is objective, efficient, fast, cheap, non-invasive, and safe. Nonetheless, further
refinements are needed to extend survey times and better include smaller size classes.
of information on the reduction of biodiversity in oil palm plantations compared to conserved forests. However, only a few studies have been performed in already anthropized matrices where almost all the natural vegetation has been replaced. To determine the effect of oil palm plantations located in an anthropized landscape on amphibian biodiversity, we obtained amphibian species richness and abundance using 48 transects distributed among seven oil palm plantation estates situated in the Gulf of Mexico lowlands in southeastern Mexico and compared with the observed amphibian biodiversity obtained from 15 previously published amphibian surveys on the area. Our survey in the oil palm plantations resulted in 1,977 individuals belonging to 15 species from seven anuran families. Although anuran diversity varies among the studied plantation estates, few significant differences were detected. We observed that the species richness in oil palm plantations represents 41.7% of the species detected in the region. However, we observed that more than half of the species (21 of 36) that have been detected in the region appeared in less than 30% of the sites studied, and the 15 remaining species that are more frequently detected in the area, 12 (80%) are present in oil palm plantations. Our study region has a long history of agricultural use and is already heavily fragmented. Thus, the remarkable similarity observed between the anuran species found in oil palm plantations and the most frequent amphibian species in the Gulf of Mexico lowlands can be explained by an already depauperate landscape dominated by species that are disturbance-tolerant or benefited from habitat modifications. Oil palm plantations in the region will expand in the future. Our results show that if the expansion continues to replace induced grasslands or other crops will have a reduced impact on the anuran biodiversity in this region. However, this expansion should preserve the remanent secondary growth forest patches distributed along the landscape to maintain the regional anuran diversity.
collected data on injuries in caimans captured during nocturnal surveys (2014–2022) in the estuary and swamps of the BRLE. We determined the sex of each caiman, measured their snout–vent length, and registered the type of injury and body region where injuries were detected. From all records, 102 of 301 caimans (33.9%) presented injuries and they were more likely to be injured in the estuary than in the swamps, probably due to the presence of a larger sympatric crocodile species in the estuary (Crocodylus acutus). Sex had no effect on the proportion of injured individuals, but larger caimans have a higher probability of being injured than smaller ones, explained by
an ontogenetic change in the individuals’ behaviors. Habitat, sex, and size class of individuals do not influence the number of injuries on different body regions. The tail was the most injured body region (17.6% of individuals), followed by the abdomen (13.0%), back (12.6%), head (9.6%), and extremities (4.0%).
For crocodylians, accurately estimating total length and demographic class usually necessitates close
observation or capture, often of partially immersed individuals, leading to potential imprecision
and risk. Drone technology offers a bias-free, safer alternative for classification. We evaluated the effectiveness of drone photos combined with head length allometric relationships to estimate total
length, and propose a standardized method for drone-based crocodylian demographic classification.
We evaluated error sources related to drone flight parameters using standardized targets. An
allometric framework correlating head to total length for 17 crocodylian species was developed,
incorporating confidence intervals to account for imprecision sources (e.g., allometric accuracy, head
inclination, observer bias, terrain variability). This method was applied to wild crocodylians through
drone photography. Target measurements from drone imagery, across various resolutions and sizes,
were consistent with their actual dimensions. Terrain effects were less impactful than Ground-
Sample Distance (GSD) errors from photogrammetric software. The allometric framework predicted
lengths within ≃11–18% accuracy across species, with natural allometric variation among individuals
explaining much of this range. Compared to traditional methods that can be subjective and risky, our
drone-based approach is objective, efficient, fast, cheap, non-invasive, and safe. Nonetheless, further
refinements are needed to extend survey times and better include smaller size classes.
l’expansion des activités humaines et la transformation des écosystèmes, la production, le transport et l’accumulation des sédiments ont été modifiés. Ces processus sont pourtant fondamentaux pour l’ensemble du bassin versant de l’Usumacinta.
Cette publication propose d’expliquer en douze questions la nature et l’importance des sédiments de l’Usumacinta : à quoi servent-ils, quel est leur rôle dans les écosystèmes, sont-ils contaminés, quels usages ont-ils eu au fil du temps, comment peut-on les valoriser ? Les réponses, rédigées par des scientifiques, contribuent à la connaissance du fleuve et à la construction d’une relation durable avec les êtres humains qui vivent sur ses rives. Ces enjeux, exposés à travers l’exemple de l’Usumacinta, peuvent être transposés à tout autre grand fleuve.
Cette publication s’inscrit dans le cadre d’une étroite collaboration scientifique entre des chercheurs mexicains et français, entre 2018 et 2022 : le projet VAL-USES « De l’usage traditionnel à la valorisation
intégrée des sédiments dans le bassin du fleuve Usumacinta ». Ce projet interdisciplinaire a été approuvé et financé par l’Agence nationale de la recherche française (ANR-17-CE03-0012-01) et le Conseil national de la science et de la technologie du Mexique (FONCICYT-290792).
Con esta publicación buscamos explicar en doce preguntas la naturaleza e importancia de los sedimentos del Usumacinta: ¿para qué se utilizan actualmente?, ¿qué usos han tenido a lo largo del tiempo?, ¿cómo pueden aprovecharse? ¿están contaminados? Nuestras respuestas buscan contribuir a la construcción de una relación sostenible entre el Usumacinta y los seres humanos que viven en sus riberas. Con este ejemplo bien podría abordarse la misma problemática respecto a cualquier otra cuenca.
Esta publicación se realizó en el marco de una estrecha colaboración científica con la participación de investigadores mexicanos y franceses que, iniciada en 2018, concluye en 2022: el proyecto VAL-USES
“Desde el aprovechamiento tradicional hacia la valorización integral de los sedimentos en la cuenca del río Usumacinta”, un proyecto interdisciplinario aprobado y financiado por la Agencia Nacional de Investigación en Francia y el Consejo Nacional de Ciencia y Tecnología en México.