Natural History of the Green Anaconda: disentangling the secrets of the world's largest snake

Movement ecology is an important tool for understanding animal behaviour toward basic needs, as well as to design conservation and management priorities. Animals usually do not move randomly and may prefer certain types of habitats over others. The yellow anaconda (Eunectes notaeus) is one of the largest snakes in South America. However, little is known about its natural history. Here, we present results from a telemetry study to quantify movement patterns and habitat use of eight yellow anacondas in a protected, seasonally flooded area in Midwestern Brazil. Yellow anacondas were associated to small channels with macrophyte stands and bushy vegetation. They moved relatively little (188 m monthly) and had small home range (mean 6.2 ha); they used native pastures and abandoned farmlands with forest patches more than expected by chance. Our results contribute to the understanding of dispersal patterns, habitat choices, and life history of this large aquatic snake and to the body of knowledge needed for management and conservation of its populations and habitats.

This chapter focuses on environmental conservation, a relatively new branch of biology that has one foot firmly set in science and the other firmly set in economics and politics. It discusses the technical aspects about anaconda management that can be used for conservation of anacondas and conservation of biodiversity in general. The most common methods of extractive wildlife management are farming, harvesting, or a combination of both. In a farming model, animals are kept in captivity, with all their needs provided by the keepers. Farming anacondas in a closed system is unlikely to be successful. However, the possibility of an open farm system exists; this has more potential of being used as a conservation tool as it requires a natural environment where the animals live. On the other end of the spectrum is harvesting or cropping. In a cropping system, animals are harvested from the wild; thus, a direct link exists between the economic activity and the conservation of the species and its habitats. The economic incentives the locals receive are directly linked to the habitat, producing clear reasons for them to protect and not overexploit natural areas. Thus, cropping has real potential to be used as a conservation tool, but like open farming, it is not conservation by itself. The author then addresses holistically the problem of conservation in Latin America and beyond.

Anaconda tells the unexpected story of the world's largest snake. Written by Jesús Rivas, the undisputed expert on the biology of anacondas, this is the first authoritative book on the biology of the green anaconda. In this book, Rivas describes his experiences over a quarter of a century, exploring the secret life of these fantastic snakes, including: their diet, movement patterns, life and tribulations, survival, behavior, and fascinating reproductive life. More than just presenting facts about anacondas, Rivas tells his story about studying them in the field. Anaconda presents a comprehensive treatment of the natural history of the elusive green anacondas. Drawing on twenty-five years of research on this reptile in the wild and in captivity, Rivas delves into the biology, behavior, demography, reproductive habits, and diet of the anaconda, as well as issues relating to its conservation. Rivas uses an ecological and evolutionary framework to present his research and supplements hard data with descriptions of his research methods, including how he tracked down the anaconda for observation and study in wild. The resulting book is a complete and engaging examination of the world's largest snake. The rich photographs provided, paired with Rivas' storytelling, makes this the perfect book for anyone looking to learn (or even learn more!) about this mysterious snake. This book is published by Oxford University press and there is no pdf available for distribution. The book can be acquired at https://global.oup.com/academic/product/anaconda-9780199732876?q=jesus%20rivas&lang=en&cc=us#

Understanding of snake ecology has increased over the past two decades, but is still limited for many species. This is particularly true for the recently described Beni anaconda (Eunectes beniensis). We present the results of a radio-telemetry study of nine (3M:6F) adult E. beniensis, including home range, and habitat use. We located the snakes 242 times in wet season, and 255 in dry season. Mean wet season home range (MCP) was 25.81 ha (6.7 to 39.4 ha); while mean dry season home range was 0.29 ha (0.13 to 0.42 ha). We found no relationship between home range size and either snout-vent length, weight, or sex. Beni anacondas seem to prefer swamps, and patujusal, while avoiding forest, and rice fields. However, habitat use by individual snakes seems to vary based on the habitats available within their respective home range. Notably, rice fields were avoided by most snakes, which suggests that this type of habitat is unsuitable for anaconda management.

Reptiles can harbor pathogenic microorganisms asymptomatically and serve as potential reservoirs of infection for humans, domestic animals, and other reptiles. Infectious diseases are also problematic for free-ranging reptile populations and are an important consideration in reptile reintroduction and translocation projects. There have been limited serologic studies of free-ranging reptiles for evidence of exposure to potential pathogens. In the present study, serum or plasma samples from five male and five female free-ranging Venezuelan anacondas (Eunectes murinus) were screened for antibodies to eastern, western, and Venezuelan equine encephalitis viruses, vesicular stomatitis virus, ophidian paramyxovirus, 19 Leptospira interrogans serovars, and Cryptosporidium serpentes. Antibodies to these agents were not detected, or antibody titers were low and possibly nonspecific. These results for the limited number of anacondas surveyed suggest that they do not serve as significant reservoirs for these infectious agents at this location.

Opportunistic finding of anacondas preying on co-specifics.

Evidence that female anacondas may eat males, likely during the breeding season

Thesis (Ph. D.)--University of Tennessee, Knoxville, 2000. Vita. Includes bibliographical references (leaves 267-284).

Sexual selection and mating systems profoundly influence the behavior and psychology of animals. Using their own studies of green anacondas (Eunectes murinus) and reviewing other recent studies, the authors conclude that incomplete data derived from a few well-studied snake species have led to general acceptance of polygyny as the dominant mating system in snakes. New data on behavior, paternity, and life history in a diverse taxonomic array of snakes support the view that polyandry is not only common in snakes but may have been the ancestral mating system. This interpretation helps to explain many seemingly paradoxical behavioral differences between lizards and snakes, such as the lack of territorial systems in most snakes and their frequent female-biased sexual size dimorphism.