Anacondas’ Tales

This chapter examines the lives and tribulations of anacondas. Anacondas, like humans, produce the same number of males and females because the sex ratio is determined by sexual chromosomes. If the sexes start out equally abundant, why would there be so many more males out there in the wild? In some vertebrates one sex or the other disperses away from the area they were born. However, the author does not believe migration plays a significant role with anacondas. For starters, males are the sex with the wanderlust, not females. As such, this would not account for the lower number of females. Moreover, migration should not be very high due to the fact that the study site is the only region that holds water, so animals might move out in the wet season, but they would likely come back in the dry season, when the author did most of the sampling. If migration is not the answer for the uneven sex ratio, one is left with mortality of females as the only explanation. If females suffered higher death rates, that could explain the male bias in the population that the model estimated. Looking further into the results of the population model, the author found that females have a lower estimated survival than males. The chapter then considers the reasons females have higher mortality. The large expenditure in reproduction females incur might result in death not only as a result of predation but also during or after feeding due to weakening.

What Is a Good Real Estate for an Anaconda?

This chapter discusses the process of tracking and tagging the anacondas. Trying to follow anacondas throughout the year gives one a new perspective about the differences between humans and snakes. Anacondas like caves. In the rivers with forested banks, the roots of the trees often hold the bank together and prevent it from being eroded away. The caves under the roots of the trees tend to be great hiding places for aquatic organisms like anacondas, caimans, iguanas, tegus, and toads. Both in dry and wet seasons, anacondas use the caves. Indeed, the presence of caves seems to be the reason that there are fewer anacondas in the parts of the creek, Caño Guaratarito, that has no trees. Interestingly, the proportion of males and females found in Guaratarito was strongly biased toward females. It seems to be a place where large snakes come to feed but does not seem to be a good place to find many males.

Science, Love, and Anaconda Research

This introductory chapter provides an overview of anaconda research. It describes the author’s experience growing up as a herpetologist in Venezuela, which has both advantages and disadvantages. The advantage is the large number and ubiquity of snakes. The disadvantages are the lack of guidance and lack of opportunities to learn. After the discovery of an illegal trade of anacondas throughout the continent, the author decided to advocate for anacondas, using a grant from the Convention for the International Trade of Endangered Species to study the most fascinating snake in the world. The chapter differentiates between two kinds of biologists: hypothesis-driven ones and organism-driven ones. Hypothesis-driven biologists seek an organism that fits their question, but organism-driven biologists find the organism they love and let the organism indicate what has to be studied about it.

Epilogue

This concluding chapter highlights the unconventional approach of the author in discussing anacondas. A conventional style would be antiseptic regarding personal views, and all opinions would be carefully removed as non-scientific. Instead, the author shared his ideas, mixed with scientific facts, opinions, and interpretations. He has done this on purpose because that is how actual humans think. Trying to remove the human from the science renders the science stereotypical and hinders its ability to address the diversity of problems because it does not have a diversity of views. Ultimately, diverse backgrounds and diverse experiences will allow for diverse questions and answers that will allow scientific thinking to evolve and move forward into new horizons. The author also considers the problem of consumerism and its effects on environmental conservation.

Conservation of Anacondas and Beyond

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.

“Hey, It’s Me, It’s Me!” Courtship and Confusion in the Male Reproductive Strategy

This chapter addresses why male anacondas are so much smaller than females. There are a number of advantages for animals to be small. Small animals have lower metabolic costs since they need to maintain only a small body that requires less food. Animals that need less food have potentially higher survival than those that have a large body to maintain. This is particularly important in droughts or times of food shortages. A small body is also an asset because it lowers the cost of locomotion. Hauling around a large body incurs larger energetic expenditures than if the body is small. This is particularly important for males that move much more than females in the mating season to track receptive females for mating. Being small also offers other benefits, such as being inconspicuous, not being a very coveted meal, and hiding easily from potential predators. Of course, there are also some disadvantages of being small. Small animals cannot fight off predators as well as large ones and are limited by their gape to what kind of prey they can eat. Furthermore, larger males may produce more sperm, which would give them an advantage in siring more offspring, particularly in those cases where the female mates with several males.

The Largess of Motherhood

This chapter assesses the reasons and limitations for large size in female anacondas. Considering how large females are—nearly five times the size of males—it is obvious that the evolutionary pressures for large size act more strongly on females than males. One aspect in which natural selection definitely favors large size in females has to do with reproductive output. The larger a female is, the more babies can develop in her body and the larger the reproductive output. Reproductive value, or lifetime reproductive success, is the number of potential offspring that an individual can leave in the population over its lifetime. There are costs animals must face when they make reproductive decisions. Some of these costs are dependent on fecundity and some of them are not, such as the risk of being preyed upon during mating or pregnancy. A young adult female that has just reached maturity is under two opposite pressures: one is to breed right away and secure a few babies into the next generation, and the other is to skip reproduction, grow larger, and make more babies in a later year. A female that is going to breed faces another decision: how to invest her breeding resources. She can produce a large number of neonates of small size or a few offspring of large size.

The Anaconda Challenge

This chapter focuses on the llanos, Venezuela’s natural floodplain, where the author decided to start his study of anacondas. The llanos is a flatland that comprises about a third of both Venezuela and Colombia. It is composed of an extensive system of natural, seasonally flooded grasslands. The llanos is located to the north and west of the Orinoco River and sits on the northern borders of the Amazon basin. Because of this, most of the wildlife of the Amazon can be found in the llanos, where it is easier to observe animals in the open vegetation of the savanna. The extreme seasonality of the llanos made all the difference in the success of the author’s anaconda research. Anacondas, being aquatic, concentrate in the few water bodies that hold water during the dry season. During this time, the chance of finding anacondas was much higher. The chapter then explores the physical build of snakes. Most snakes have adaptations of the skull and jaws involving mobile hinges, and a whole arrangement of joints and muscles evolved for swallowing large prey. The extra mobility of the snake’s jaws is obtained by giving up solid skull sutures that the ancestral lizards had, rendering the snake’s head more vulnerable to damage.

The Origin of the Mystery

This chapter traces the paleo-history of South America to tackle evolutionary questions about anacondas. Going back in history 150 million years ago, the current continents of South America and Africa were joined in a single mega-continent that also included current Australia and Antarctic. In the northern part of this continent (current South America and Africa) was a large river that started roughly where the current Congo River starts and drained the continent out of what is currently western Ecuador. Approximately 110 million years ago, South America separated from Africa and drifted west. The continent was drained by the paleo-Amazon. As South America drifted west, it collided with the Nazca plate in the eastern Pacific. As the two landmasses moved against each other, the Nazca plate subsided under South America, pushing up the western border of the latter, giving rise to the Andes. The creation of the Andes would result in the eventual closing of the drainage of the paleo-Amazon into the Pacific Ocean. The chapter looks at the significance of this paleo-history to the evolution of anacondas. It seems like the conditions in the paleo-history of the continent of constant flooding were not all that different from the conditions that anacondas encounter currently in the llanos.

How Big Can a Giant Be?

This chapter determines the maximum size that anacondas can reach, which has been the subject of long-standing debate among herpetologists. There are many accounts of snakes around 9 to 11 meters (29.5 to 36 feet). A lot of the controversy concerns the credibility of the records, the confusion created by the fact that the skins stretch when the snakes are skinned, and the use of estimates or unreliable methods of measurement. The largest snake that the author has caught, out of nearly 1,000 animals, was only a little more than 5 meters (16.4 feet) long. What is the reason for such a difference? Due to their slow growth rate, anacondas require a long time to reach a large size. The author’s study area is a cattle ranch where the protection of wildlife is a relatively recent practice. Presumably, the really large animals might have been killed off earlier and the animals that exist now in the areas where the author studied might not have had enough time to grow to really large sizes. However, this is not all that there is to it. The chapter then considers the constraints of large body size in anacondas, especially female ones. It also describes the discovery of the fossilized remains of a snake of formidable proportions in eastern Colombia, Titanoboa cerrejonensis, and makes predictions about its size and natural history.