Conservation and geographic distribution of crocodylians in Bolivia (Caiman yacare, Caiman latirostris, Melanosuchus niger, Paleosuchus palpebrosus, Paleosuchus trigonatus)

Crocodylians are large predators and ecological keystone species in wetland ecosystems. In Bolivia a total of five species occur, all of which are members of the family Alligatoridae: Caiman yacare, C. latirostris, Melanosuchus niger, Paleosuchus palpebrosus, and P. trigonatus. Beginning in the mid-1800s, wild populations were reduced and threatened by unsustainable exploitation, commercial hunting, lack of wildlife law enforcement, and poor management strategies. Economic incentives that can be generated through the management of crocodylians and sustainable use of wildlife (SUW) programs have become key elements for conservation of the species and their habitats. Nevertheless, these programs must be designed based on solid scientific strategies to guarantee efficiency and sustainability. Adapted from successful conservation strategies and distribution modeling techniques, I present the first country-wide range assessment of the current state of knowledge of crocodylians in Bolivia, propose regional conservation priorities that integrates the distribution and biological information of the five focal species in Bolivia, and improve the estimation of suitable habitats currently occupied by Caiman yacare, known as the Area of Occupancy (AOO), based on Maxent modeling, maintaining consistency with the IUCN Red List assessments. I carried out a literature search and review, and spatial data compilation to estimate the distribution range (Extent of Occurrence - EOO), characterize ecoregions (Crocodylian Geographic Regions - CGRs), and delineate areas with species occurrence and population surveys (Crocodylian Study Units – CSUs). Ecoregions inside CSUs were defined as Crocodylian Conservation Units (CCUs), for which I developed a geographic priority setting. I categorized them as Regional Habitat Priority (RHP) areas with sufficient biological information to implement management and sustainable use programs aimed at species and habitat conservation, or as Regional Research Priority (RRP) areas with the absence or insufficiencies of biological information to prioritize research and monitoring programs. Then, I used a high-quality distributional data and defined specific tuning parameter settings in Maxent to estimate the Area of Occupancy for Caiman yacare. I reviewed 105 documents written from 1977 to 2017 and used spatial data from 44 documents. I estimated an EOO of 654,930 km2, defined 17 CGRs, 98 CSUs, and 167 CCUs, out of which 29 were categorized as RHP and 138 as RRP. I estimated an area 364,656.68 km2 as the potential AOO for Caiman yacare, representing the 33.65% of the country extent. This extent is justified by accurately representing the habitat requirements of the species and have been validated through an independent model evaluation, following the requirements of the IUCN Red List assessments. This study is the first effort to develop a regional conservation plan as a scientific baseline that can facilitate decision-makers to prioritize future research, encourage habitat protection, and promote management and sustainable use programs. Furthermore, Maxent clearly constitutes a promising tool for modeling suitable habitat of potential crocodylian species distribution, applicable in many areas of ecological research (e.g., relative abundance, population structure, population dynamics, population trends) that, undoubtedly, will generate relevant information to achieve more successful management planning strategies and guarantee the effective long-term conservation of crocodylians in Bolivia and potentially, throughout the world.