Rediscovering the Apaporis Caiman (Caiman crocodilus apaporiensis): Notes from a Long-Anticipated Expedition
Abstract and Figures
Caiman crocodilus apaporiensis has been of particular interest because of its clearly differentiated morphotype within the Spectacled Caiman complex. Information on the biology of C. c. apaporiensis is incomplete because of its restricted distribution in the inaccessible middle and upper Apaporis River in Colombia. I undertook an expedition to the middle Apaporis River basin in an attempt to validate the presence of C. c. apaporiensis through observations on morphometry, ecology, and ethnozoology. Previously described skull characteristics were clearly differentiable in both adults and subadults in the region. However, because many individual C. c. apaporiensis that were either captured or visually assessed were relatively small, some skull characteristics more closely resembled the more general C. crocodilus morphotype. Although data on population size and distribution of C. c. apaporiensis remain limited, information gleaned from local inhabitants indicates that the subspecies is common in the middle Apaporis River. Population parameter and molecular phylogeography studies could lead to management practices that would protect the genetic integrity of C. c. apaporiensis by minimizing subspecific interbreeding.
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... Entonces, en 2018, Balaguera-Reina (2019) El ejemplar recolectado en el presente trabajo es un juvenil (Figura 3g); por su coloración, que es amarillo oscuro y la forma del rostro que no es angosto se parece más a los ejemplares de otras poblaciones del complejo C. crocodilus. Cabe aclarar que las características morfológicas en los juveniles de C. c. apaporiensis no son claras para poder realizar una determinación más precisa (Medem 1955, Balaguera-Reina 2019. ...
Resumen El inventario de anfibios y reptiles en la cuenca del río Apaporis se realizó en el marco de la iniciativa Colombia BIO (Minciencias); el esfuerzo de muestreo se centró en las localidades de Buenos Aires y Cerro Morroco, cuenca media del río Apaporis; en Cerro Azul-Cerro Campana, cuenca alta, y en el raudal de Jirijirimo. A partir de la búsqueda en bosques, aflo-ramientos rocosos y raudales se reportan 41 especies de anfibios de los cuáles se destaca el registro de una familia nueva para el país, Ceuthomantidae y una especie indescrita, la confirmación de la pre-sencia de O. vilarsi en Colombia y el hallazgo de otra especie de la familia Craugastoridae por describir. En reptiles se encontraron 33 especies, se recolectaron ejemplares de algunas poco conocidas o que tienen una distribución relativamente pequeña en la parte noroccidental de la Panamazonia y muy relacionadas con el Escudo Guayanés. Se destacan los registros de Bachia pyburni, Neusticurus medemi, Helicops hagmanni y la tortuga Rhinemys rufipes.
Abstract The inventory of amphibians and reptiles in the Apaporis River basin was carried out within the framework of the Colombia BIO initiative (Minciencias). The sampling effort was focused on the towns of Buenos Aires and Cerro Morroco, in the middle basin of the Apaporis River; in Cerro Azul-Cerro Campana, upper basin, and in the Jirijirimo torrent. The search in forests, rocky outcrops, and torrents allowed the report of 41 species of amphibians, of which the record of a new family for the country, Ceuthomanti-dae, an undescribed species, the confirmation of the presence of O. vilarsi in Colombia, and the discovery of another species of the Craugastoridae family yet to be described stand out. 33 species of reptiles were found, and some little-known specimens or with a relatively small distribution in the northwestern part of the Pan-Amazon and closely related to the Guiana Shield were collected. The records of Bachia pyburni, Neusticurus medemi, Helicops hagmanni and the turtle Rhinemys rufipes stand out.
... Population ecology studies on spectacled caimans in Colombia have been highly concentrated on regions such as the Caribbean (Barahona et al. 1996, Ulloa and Cavanzo 2003, Cavanzo 2004 (Forero-Medina et al. 2006), and the Amazon (Naranjo 1996, Balaguera-Reina 2019. Most of these studies were performed across periods of time less than a year, which implies they were missing at least part of the story due to the effects of environmental annual cyclical variables (e.g., temperature, precipitation) on population parameters (e.g., number of individuals, demographic structure; Balaguera-Reina et al. 2018). ...
Population ecology studies on spectacled caimans (Caiman crocodilus) in Colombia have been few and far between with many covering short periods and defining population parameters based on relative indices (i.e., individuals/km). This reflects a lack of information on the general effects that environmental variables have on annual cycles of population dynamics, as well as a bias in abundance estimations due to the uncertainty of detection error. Keeping this in mind, we assessed the abundance and demographic structure of the spectacled caiman population inhabiting the Apaporis River middle basin over a year, based on robust hierarchical model that accounts for imperfect detection. We recorded a total of 1156 caiman observations between December 2018 and November 2019, estimating an average predicted value for abundance across all surveys of 29.99 ± 13.17 individuals, slowly increasing as the transect length increases and increasing variation as months passed by. The average detection probability was 0.69 ± 0.25 across all surveys, with no apparent effect as water temperature and relative humidity change across space-time and slowly decreasing as months go through. The population size estimated based on the top-performing model was 1763 ± 786 caimans across ~7.1 km2 assessed. We estimate the commonly used relative abundance (encounter rate) index as well as a generalized linear model and discuss how those relate with the values predicted by N-mixture models. We also discuss the relevance and cautions researchers should have when using N-mixture models to better understand spectacled caiman ecology.
Caiman crocodilus, comúnmente llamada como ‘’caimán de anteojos o babilla’’, es una especie de aligatórido que se distribuye naturalmente a lo largo del continente americano (desde México hasta Perú y Brasil) con poblaciones introducidas y asentadas en los Estados Unidos (incluyendo Puerto Rico) y Cuba. Esta especie se encuentra actualmente dividida en tres subespecies válidas (C. crocodilus fuscus, C. crocodilus chiapasius y C. crocodilus crocodilus), ya que recientemente se justificó molecularmente la invalidez de C. c. apaporiensis, agrupándola como una variación morfológica de C. c. crocodilus. Posee una arista ocular particularmente notoria en la parte anterior de sus parpados además de otras características morfológicas que la hace fácilmente reconocible y es de importancia comercial a lo largo de su distribución. Pese al reconocimiento de la especie a lo largo del territorio, su estudio se ha centrado en producción, comercio y uso dejando a un lado el estudio de poblaciones silvestres y su interacción e importancia en los hábitats en los que está presente. la presente monografía tiene como objetivo evaluar el estado conocimiento sobre C. crocodilus en Colombia con el fin de comprender de manera efectiva vacíos y prioridades de investigación para su uso y conservación. Para lograr esto se realizó una revisión exhaustiva de bases de datos, herramientas de investigación, páginas web, software y complementariamente se generó un mapa de la distribución actual de la especie. Se recopilaron 198 documentos asociados a la especie divididos en las siguientes categorías: general, aplicación y aprovechamiento, conservación, distribución, ecología y sistemática. La mayoría de la información se asoció a la categoría de aplicación y aprovechamiento. Los resultados indican que la mayoría de los documentos a nivel regional provienen del Caribe, donde se desarrolla en gran medida los procesos de zoocria. Parece ser que el principal interés que genera la especie es su valor comercial lo que hace esencial priorizar los estudios en estado silvestre porque, aunque la especie no se encuentre amenazada, su mal manejo histórico podría estar afectando su conservación.
The spectacled caiman (Caiman crocodilus) is currently considered to be a species complex due to the relatively high morphological and molecular diversity expressed across its range. One of the populations of interest, inhabiting the Apaporis River (Colombia), was described based on skull features as an incipient species (C. c. apaporiensis) and has been treated by some authors as a full species. Recent molecular work challenged this hypothesis, because relatively low mitochondrial molecular differentiation was found between the morphologically described Apaporis caiman and C. crocodilus (s.s.) Amazonian populations. Here, we present an update on the topic based on a larger molecular sample size and on analysis of expanded geometric morphometric data that include six newly collected skulls. Morphometric data support the existence of previously recognized morphotypes within the complex in Colombia and demonstrate that the newly collected material can be assigned to the classic Apaporis caiman morphotype. However, our expanded genetic analysis fails to find appreciable mitochondrial molecular divergence of the Apaporis caiman population from the C. c. crocodilus population (COI-CytB: Amazon Peru 0.17 ± 0.06%, CytB-only: Caquetá River Colombia 0.08 ± 0.07%). The Apaporis caiman is interpreted to be a phenotypically distinct member of the cis-Andean C. crocodilus metapopulation that has not yet achieved (or may not be undergoing at all) appreciable genetic differentiation. Thus, it should not be considered a fully independent evolutionary lineage, nor given full species rank.
Caiman crocodilus is a species of alligator that is distributed throughout the American continent, from the southern United States to the north of Bolivia. It currently has three valid subspecies C. crocodilus fuscus, C. crocodilus chiapasius and C. crocodilus crocodilus, because it was recently described that the subspecies C. crocodilus apaporiensis really is a morphological variation of the subspecies C.c. crocodilus. This species is commonly called as ‘’ spectacled caiman’’ due to the edge that forms in the anterior part of its eyes, in Colombia it is known as ‘’Babilla’’ and is usually recognized in practically all the departments of the country due to its commercial use and its extensive distribution. Despite the recognition of the species throughout the territory, its study focuses on production, trade, and use, leaving aside its study in wild populations and its interaction and importance in the habitats in which it is present, therefore, a bibliographic review is necessary to evaluate the state of knowledge of the species in Colombia and effectively understand the key points for its use and conservation. To achieve this, an exhaustive review of databases, research tools, web pages, software was carried out and a map of the current distribution of the species was generated. 198 documents associated with the species were collected and divided into the following categories: general, application and use, conservation, distribution, ecology and systematics. Most of the information was associated with the category of application and use. The results indicate that most of the documents at the regional level come from the Caribbean, where zoocria processes are largely developed. It seems that the main interest generated by the species is its commercial value which makes it essential to prioritize studies in the wild because, although the species is not threatened, its historical mismanagement could be affecting its conservation.
Studies on the biology of Caiman crocodilus have drawn attention to its biology with emphasis on systematic, taxonomy and ecology. However, anatomical aspects, such as skull characteristics, have not been studied in detail throughout its geographic range. In this study the skull characteristics for C. crocodilus subspecies, C. c. fuscus, C. c. chiapasius, C. c. crocodilus, and C. c. apa-poriensis were analyzed using geometric morphometrics and descriptive morphology, including geographic and ontogenetic variation. Variation in skull morphology was found between the subspecies analyzed. Trans-Andean subspecies, C. c. fuscus and C. c. chiapasius, exhibit breviros-trine skulls but they are different in the contact between frontal and nasal bones and the size of the palatine process of the maxilla; therefore, populations in Colombia correspond to C. c. fuscus and, C. c. chiapasus is not distributed in Colombia. Although cis-Andean subspecies, C. c. apaporiensis and C. c. crocodilus, have longirostrine skulls, both subspecies differ in the shape of the skull and in osteological characters; then, adults of C. c. apaporiensis present frontal and nasal in contact and, V-shape maxillary-premaxillary suture; while C. c. crocodilus specimens exhibit a high geographic and ontogenetic variation, supporting the hypotheses that there at least two clades of such subspecies for Colombia. These morphological differences should be considered in future systematics studies and policies on global conservation of the different C. crocodilus subspecies.
The order Crocodylia contains the sole reptilian survivors of the Archosauria, which also includes the dinosaurs and birds. While the living forms are not nearly as diverse as they have been in the past, they represent a lineage that first appeared in the Mesozoic Era, and that has successfully survived a number of extinction events. They also represent a group that has been seriously impacted by humans, both in terms of hunting and habitat destruction. Crocodylyians are, therefore, largely protected or endangered. However, they are critical apex predators that often serve as ‘keystone’ species and indicators of the health of the environments that they inhabit.
Key Concepts
The Crocodylia (the only living non‐avian Archosaurs) are aquatic or semi-aquatic apex predators that can trace their origins to the early Mesozoic Era.
The three recognized families, Alligatoridae, Crocodylidae and Gavialidae, are currently represented by some 30 named forms found primarily in tropical or subtropical environments.
The combination of human hunting for their meat and skins, habitat loss and long generation times have contributed to the threatened or endangered status of many living crocodylians.
Even though most recognized species seem to be valid hybridization, especially within the genus Crocodylus, is common and complicates efforts to understand their recent evolutionary history; growing evidence among several caiman species suggests that hybridization is more prevalent than previously thought.
Molecular analyses in conjunction with assessments of morphological variation and paleontology are contributing to a more accurate understanding of crocodylian phylogeny, particularly within Crocodylidae and Gavialidae.
Advances in molecular biology and genetics are revealing that many recognized crocodylian species are complexes of two or more cryptic species. These discoveries will have a profound impact on interpretation of the crocodyliform fossil record. Our understanding of ranges of intraspecific variation in modern crocodylian morphology may be based on multiple species and thus express both intraspecific and interspecific variation. This raises questions about our ability to recognize modern species in the fossil record, and it also indicates that specimens from disparate localities or horizons may represent not single widespread species, but multiple related species. Ranges of variation in modern species require a thorough re-evaluation, and we may have to revisit previous perceptions of past crocodyliform diversity, rates of evolution or anagenetic lineages in stratigraphic succession. These challenges will not be unique to those studying crocodyliforms and will require sophisticated approaches to variation among modern and fossil specimens.
The Apaporis caiman (Caiman crocodilus apaporiensis) has been of particular interest due to its highly differentiated morphology. However, no molecular research has been done to clarify its taxonomy. We characterized the genetic variation within C. crocodilus by assessing the evolutionary trajectory of Apaporis caiman populations using mitochondrial molecular markers. We collected ten Apaporis caiman samples from the middle basin of the Apaporis River, Colombia, sequenced two mitochondrial genes [cytochrome oxidase I (COI) and cytochrome B (CytB)], and analysed them together with all available sequences from homologous gene fragments at GenBank for the species. Phylogenetic reconstructions revealed three main clades clearly differentiated across the C. crocodilus complex. These clades matched genetically and geographically with three of the four subspecies currently recognized (C. c. chiapasius, C. c. fuscus and C. c. crocodilus). However, we found low to almost non-existent genetic differentiation between C. c. crocodilus and the until-now morphologically recognized C. c. apaporiensis, suggesting that the latter is part of the genetic spectrum present within C. c. crocodilus. We reject the hypothesis of an expected elevated level of genetic variation due to isolation (supported by morphological differentiation) and support the idea of Apaporis caiman populations as a C. crocodilus ecomorph.
Conservation of large predators has long been a challenge for biologists due to the limited information we have about their ecology, generally low numbers in the wild, large home ranges and the continuous expansion of human settlements. The American crocodile (Crocodylus acutus) is a typical apex predator, that has suffered from all of these characteristic problems, especially the latter one. Humans have had a major impact on the recovery of this species throughout its range, even though most of the countries it inhabits have banned hunting. The last decade has made it clear that in order to implement sound conservation and management programs, we must increase our understanding of crocodile spatial ecology. However, in only two countries where American crocodiles have telemetry studies even been published. Herein we have characterized the spatial ecology of C. acutus on Coiba Island, Panama, by radio-tracking (VHF transmitters) 24 individuals between 2010 and 2013, to determine movement patterns, home range, and habitat use. We have then compared our findings with those of previous studies to develop the most comprehensive assessment of American crocodile spatial ecology to date. Females showed a higher average movement distance (AMD) than males; similarly, adults showed a higher AMD than sub-adults and juveniles. However, males exhibited larger home ranges than females, and concomitantly sub-adults had larger home ranges than juveniles, hatchlings, and adults. There was an obvious relationship between seasonal precipitation and AMD, with increased AMD in the dry and "low-wet" seasons, and reduced AMD during the "true" wet season. We found disaggregate distributions according to age groups throughout the 9 habitat types in the study area; adults and hatchlings inhabited fewer habitat types than juveniles and sub-adults. These sex- and age-group discrepancies in movement and habitat choice are likely due to the influences of reproductive biology and Coiba's precipitation cycle. Juveniles also showed distinct movement patterns and home ranges; however, with sexual maturation and development, these behaviors became more characteristic of adults and sub-adults. Ours is one of a very small number of studies that will allow future management and conservation planning to be based on the comprehensive integration of the spatial ecology of a Neotropical crocodylian apex predator.
Caiman crocodilus and C. yacare are economically valuable species afforded legal protection both within the United States and around the world. While five populations of these species have received formal taxonomic recognition between 1758 and 1955, there has never been an analysis of variation across populations representing the entire range of these species. We examined 13 external morphological characteristics in 360 individuals from known localities distributed throughout the range of these taxa. Using covariance, principal component and discriminant function analyses, we find no defensible basis for the partition of C. crocodilus into subspecies, nor do we feel that considering C. yacare a subspecies of C. crocodilus, as proposed by some, is warranted. The implication of these findings for enforcement of current legislation is discussed.
Wildlife species have been recognized as sentinels of environmental health for decades. In fact, ecological data on various wildlife populations provided the impetus for banning some organochlorine pesticides over the last few decades. Alligators are important sentinels of ecosystem health in the wetlands of the southeastern United States. Over the last 15 years, a series of studies have demonstrated that environmental exposure to a complex mixture of contaminants from agricultural and municipal activities alters the development and functioning of alligators' reproductive and endocrine systems. Further studies of basic developmental and reproductive endocrinology in alligators and exposure studies performed under controlled laboratory conditions support the role of contaminants as causal agents of abnormalities in gonadal steroidogenesis and in reproductive tract development. These studies offer potential insight into environmentally induced defects reported in other wildlife and human populations exposed to a wide array of endocrine-disruptive contaminants.
We radio-tracked five male and eight female estuarine crocodiles (Crocodylus porosus) in a non-tidal waterhole in Lakefield National Park in northern Queensland during the late dry/mid-wet season (2003-04) and the following dry season (2004). Individual crocodiles occupied larger home ranges (River Channel Areas (RCA) during the late dry/mid-wet season (10.64 ± 2.86 ha) than in the dry season (3.20 ± 1.02 ha), and males occupied larger home ranges (23.89 ± 2.36 ha) than females (5.94 ± 1.34 ha) during the late dry/mid-wet season. There were no obvious differences in home range between sexes during the dry season. During the late dry/mid-wet season, adult males often travelled long distances along the waterhole while females moved less. During the dry season, movement patterns were quite variable, with no clear difference between sexes. All crocodiles were most active from late afternoon (1500-1800 hours) until midnight. Individual home ranges (RCA) overlapped considerably during the late dry/mid-wet season. The extent of home-range overlap between three adult males and the number of times they either passed each other or were located near each other was particularly striking. Previous research has come to conflicting conclusions about the extent of territoriality in wild estuarine crocodiles, although it has been widely believed that males are highly territorial. The findings imply that large adult male estuarine crocodiles are not highly territorial in non-tidal freshwater systems that are geographically confined.
Caiman crocodilus apaporiensis has been considered by several authors as an extreme of morphological variation within the Caiman crocodilus complex. Here, we evaluate its position in the Caiman crocodilus complex morphospace using morphological traits from head shape. We examined the holotype and seventeen paratypes of Caiman crocodilus apaporiensis Medem 1955 deposited at the Field Museum of Natural History. We performed multivariate morphometric analyses: principal component analysis (PCA) and discriminant function analysis (DFA), based on 21 cranial traits of of C. c. apaporiensis, C. yacare and the C. crocodilus complex (C. c. chiapasius, C. c. fuscus andC. c. crocodilus). We find a notable separation of C.c. apaporiensis from C. yacare and C. crocodilus complex in the morphospace. We suggest that geographic isolation might have driven this morphological separation from the C. crocodilus complex, but further analysis are necessary to confirm whether these differences are related with genetic differentiation within the complex. In addition, we suggest that environmental heterogeneity might drive the evolution of independent lineages within the C. crocodilus
complex.
Attempts to assess the natural affinities and evolution of living crocodilians have been difficult and largely contradictory (Kalin, 1955; Steel, 1973; Dowling and Duellman, 1974). Morphological character analysis has been misleading due to the overall conservatism of these reptiles and to the tendencies toward parallelism and convergence of traits that has occurred during their evolution (Langston, 1973). These complications, together with the lack of critical fossils, have made paleontological interpretations extremely difficult (Sill, 1968; Hecht and Malone, 1972; Langston, 1973; Buffetaut, 1979). Because of such problems and the small number of living species, morphoclines are rare, further complicating the efforts of the comparative morphologist (Hecht and Malone, 1972).
To study the Earth system and to better understand the implications of global environmental change, there is a growing need for large‐scale hydrographic data sets that serve as prerequisites in a variety of analyses and applications, ranging from regional watershed and freshwater conservation planning to global hydrological, climate, biogeochemical, and land surface modeling. Yet while countless hydrographic maps exist for well‐known river basins and individual nations, there is a lack of seamless high‐quality data on large scales such as continents or the entire globe. Data for many large international basins are patchy, and remote areas are often poorly mapped.
In response to these limitations, a team of scientists has developed data and created maps of the world's rivers that provide the research community with more reliable information about where streams and watersheds occur on the Earth's surface and how water drains the landscape. The new product, known as HydroSHEDS (Hydrological Data and Maps Based on Shuttle Elevation Derivatives at Multiple Scales), provides this information at a resolution and quality unachieved by previous global data sets, such as HYDRO1k [ U.S. Geological Survey (USGS) , 2000].