Jesus Rivas

New Mexico Highlands University · Biology

While elucidating the evolutionary trajectory of green anacondas, we previously documented the existence of two distinct species, Eunectes akayima sp. nov. and Eunectes murinus (Linnaeus, 1758), that separated approximately 10 million years ago. Our research integrates a novel molecular clock approach, focuses on tectonic plate movements with fossi...

Anacondas, genus Eunectes, are a group of aquatic snakes with a wide distribution in South America. The taxonomic status of several species has been uncertain and/or controversial. Using genetic data from four recognized anaconda species across nine countries, this study investigates the phylogenetic relationships within the genus Eunectes. A key f...

Introduction Trophic cascades can produce important effects on a community where some species may have strong effects on other parts of the community up, down the food chain, or both. Top predators are often controlled from the bottom-up by the abundance of their prey base while prey animals are often controlled from the top-down. Studies of trophi...

Introduction: Trophic cascades can produce important effects on a community where some species may have strong effects on other parts of the community up, down the food chain, or both. Top predators are often controlled from the bottom-up by the abundance of their prey base while prey animals are often controlled from the top-down. Studies of troph...

Capital breeders are animals that breed with the stored energy they have gathered prior to the reproductive event. The amount of energy stored by a given individual can be quantified using morphological measurements and estimating a condition index that can help study the reproductive biology of wild-caught animals. Several condition indices have b...

The maximum size that snakes can reach has been a matter of long held debate until the discovery of Titanoboa cerrejonensis (Boidae). It was an aquatic predator that lived 60–58 million years ago in what is currently eastern Colombia, occupying tropical swamps. It was calculated to measure 12.82 metres and it was speculated that it grew so much due...

Chapters describe the conservation status of Crocodilyans in centra-western Brazil

Understanding the origin of South America's diversity is of great importance especially considering our current extinction crisis in the face of climate change. While great debate exists about the sources of Amazonian diversity, there is no consensus about an overarching process that explains the Amazon's uniquely high diversity. In this contributi...

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 me...

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, inclu...

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...

Analysis of evolutionary roots of sharing, altruism, leading to socialist modes of production in human societies

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...

Our knowledge of the biology of neonatal snakes has lagged behind that of adult animals, mostly due to the difficulty of finding and studying neonatal snakes in the wild. Traditional approaches view neonatal reptiles as miniature replicates of their adult counterparts. In this contribution, we present data on the natural history of neonatal Green A...

Osteomyelitis is frequently reported in turtles, lizards and snakes and Salmonellae are increasingly reported as the causative organism. However, very little is known of this disease occurring in crocodilians. Crocodilians are shy, robust animals and often hide clinical symptoms, especially when submerged in water. Knowledge of disease in crocodili...

Invasive species are a leading conservation for native species worldwide. The American Bullfrog (Lithobates catesbianus), native to eastern United States, is widely established in northern New Mexico. Most studies on invasives are limited to the eradication of the invasive but few efforts are made to understand the biology of the invasive and the n...

Opportunistic finding of anacondas preying on co-specifics.

The article revises issues of political change in the US and in the rest of the Americas. The urge for change of the people across the continent is what lead to the election of Barack Obama and will continue leading the politics of the US, despite of what Obama does during his tenure. Change may come in different ways, there is not a scripted path...

The way that herpetologists have traditionally measuredlive snakes is by stretching them on a ruler andrecording the total length (TL). However, due to the thinconstitution of the snake, the large number of intervertebraljoints, and slim muscular mass of most snakes,it is easier to stretch a snake than it is to stretch anyother vertebrate. The resu...

Survey of tick population on the black iguanas of Palo Verde.

Manuscript revises aspect of the evolved human nature that predisposes us to live or seek socialist systems. Contrary to popular believe, evolution does not select for the most selfish, rather, cooperation played an important role in the evolution of human beings. This tendency to cooperate, predisposes humans to live in socialist and cooperative e...

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 s...

The fifty-seven original essays in this book provide a comprehensive overview of the interdisciplinary field of animal cognition. The contributors include cognitive ethologists, behavioral ecologists, experimental and developmental psychologists, behaviorists, philosophers, neuroscientists, computer scientists and modelers, field biologists, and ot...

Neonate green iguanas exhibit risky behavior in the presence of simulated or actual predators. This differences may be the result of altruism via kin selection in neonate iguanas

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...

S exual size dimorphism (SSD) is widespread in almost every group of animals, generating great scientific interest (Andersson 1994). Most research has been on species in which males are larger than females. Expla-nations tend to focus on the advantages of size for direct male–male competition over access to fertile females or resources needed by fe...

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).

Using a sock placed over the snake head and securing it with a stretch of electrical tape behind the cuadrate bone the snake is rendered harmless and much calmer which makes it easy to process and collect data