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| Ecologist Everton Miranda and a snake of the species sucuri-amarela (Eunectes notaeus) |
Reptiles have been the victims of prejudice in many ecological studies. This is the opinion of the ecologist Everton Miranda, of the Mato Grosso State University (Unemat), campus of Alta Floresta, Mato Grosso state, Brazil. According to him, such a prejudice would translate into fewer scientific studies focused on the ecology of snakes, lizards or tortoises when compared to the avalanche of work that exists on the ecology of mammals and birds, groups of animals that Miranda defines - jokingly - as "plush fauna".
Recently, Miranda published an article pointing out this problem, and arguing that biologists should devote more attention to reptiles. Read below an interview where Miranda puts his opinions and proposes ways for science to give due attention to reptiles, highly interactive animals.
PETER MOON
Recently, you have published the article "The Situation of Reptiles as Ecological Actors in the Tropics" (The Plight of Reptiles as Ecological Actors in the Tropics), where you advocate a paradigm shift in our understanding of the role of large reptiles in tropical ecosystems. What motivated you to write it?
Everton Miranda - I wanted to stimulate a reaction against the prejudice that reptiles are subjected to in much of the research on ecology. Reptiles are frequently ignored in ecological studies, despite being highly interactive animals.
Can you talk a bit more about this?
Miranda - When ecological interactions are in question, the focus is mainly on charismatic animals. It's how ecologists call mammals and certain groups of birds - "cute", "plush" animals - that appeal more to the public and to many scientists.". In the scientific literature on megafauna, animals over 45 kg, reptiles such as tortoises, alligators, crocodiles and large snakes are largely ignored.
Can you name a few large reptiles neglected by science?
Miranda - In the last decades, centuries and millennia, Earth's tropical ecosystems have witnessed extinctions of hundreds of large reptiles. Several extinctions of large reptiles over the past 50,000 years are directly related to the emergence of primitive and modern humans. The species of large-sized reptiles that have managed to survive the contact with humans have suffered drastic reductions to its distributions and abundances. In Brazil, the range of some important mega-reptile species have been drastically reduced. It is the case of the bushmaster (Lachesis muta rhombeata), a snake that today is distributed across very few fragments of the Atlantic forest. Another interesting case is the yellow-footed tortoise (Chelonoidis denticulatus), a tortoise that is an important seed disperser, that was also extirpated from most of its distribution in the Atlantic Forest.
What about extinct groups, which groups do you refer to?
Miranda - Late quaternary megafauna extinctions are widely documented in the scientific literature as well as in a variety of popular media, featuring mammoths, woolly rhinoceroses, glyptodonts, saber-tooth tigers, and other known figures. Even birds - which are rarer in the megafauna category - have a guaranteed place in this branch of knowledge, with the best-known examples being New Zealand’s moas and Madagascar’s elephant birds. But in addition to these charismatic examples, little is said of the reptilian wonders that we have extinguished, such as the giant horned tortoises (Meiolania spp.) from Australia, the horned crocodile (Voay robutus) from Madagascar and a huge number of extinct island species during the transition from the Holocene to the Anthropocene, the last 10,000 years. There were gigantic iguanas in Fiji, and a 60 cm gecko in New Zealand!
And in South America and the Caribbean?
Miranda - In Brazil there are fossil findings that indicate the existence of continental giant tortoises in Serra da Capivara (Piaí state, Brazil). These fossils are still waiting for a scientific description. here were also giant tortoises (Chelonoidis lutzae) in the north of Argentina until the arrival of our species.
The Cuban crocodile is only “Cuban” because our species restricted their distribution to that island: this animal - intelligent, gregarious and well equipped to feed on terrestrial animals - occurred throughout much of the Caribbean, not just Cuba. Among its prey were several species of giant tortoises of the genus Chelonoidis and Hesperotestudo, this last one related to the burrowing tortoises of continental America. The arrival of our species devastated the trophic webs of the Caribbean islands, extinguishing and extirpating iguanas, giant tortoises and crocodilians.
You state that the importance of reptiles in most tropical ecosystems has been neglected, and that this may be misleading. Can you tell us more about this?
Miranda - It may be a misleading paradigm to assume that the complex ecological relations of the tropics are independent of important predators such as crocodilians, seed dispersers as important as tortoises, and of fundamental elements in the connection between terrestrial and oceanic ecosystems such as sea turtles. The way each of these processes is currently described usually ignores the role of reptiles and their importance as megafauna. Size has important consequences for the ecological interactivity of an organism, and many tropical reptiles are enormous. Assuming they are irrelevant elements of ecological processes in tropical ecosystems is not only wrong but dangerous.
What ecosystem processes performed by large reptiles are still poorly known?
Miranda - The role of predatory reptiles such as crocodilians and large snakes (anacondas and pythons) is still little known. These animals are seldom selective regarding their prey. They have the potential to regulate the population of their prey by controlling access to water, in addition to direct regulation via predation.
Seed dispersal by large turtles and tortoises, which have great potential as dispersers, is still poorly studied and has only been explored in a few South American species. Nothing is known about the dispersal by giant continental turtles such as the African spurred tortoise (Centrochelis sulcata) or by the Asian forest tortoise (Manouria emys), for example.
The role of tortoises in the flow of nutrients and matter from aquatic to terrestrial ecosystems is also poorly understood. Large tortoises such as the Amazonian turtle (Podocnemis expansa) carry large amounts of nutrients from water to land. This diversity of interactions carried out by reptiles in tropical ecosystems needs to be better understood.
You suggest that the past and present ecological processes carried out by large reptiles may be orders of magnitude greater than what is currently perceived. Can you tell us more about this? Give me an example to illustrate what you mean.
Miranda - Amazonian turtles, which easily reach 60 kg, nest by the tens of thousands on beaches of Amazonian rivers. Although these tortoises still show up in large numbers on some well-protected beaches in the Amazon, descriptions made by early naturalists visiting the Amazon basin in the 16th century report rivers that could not be crossed because of the abundance of these animals. The largest city in the Amazon was for decades illuminated with oil extracted from the eggs of this turtle: 200 million eggs per year for the city of Manaus alone! It can be assumed that these animals occurred in greater abundance in the past, and thus their interactivity would be superior in key processes such as seed dispersal and nutrient flow between aquatic and terrestrial environments, as well as prey to animals like jaguars and alligators.
What are your suggestions for starting to change this picture?
Miranda - A direct dissemination effort to stimulate the research of ecological interactions promoted by large reptiles. The film "Jurassic Park", of 1993, raised interest in paleontology, a trend that continued until nowadays. I believe the same can be done with modern large reptiles, with the realization of new documentaries, books and articles disseminating scientific information about the reptilian megafauna and their functions.
Could you cite actions in this direction that are already being successfully carried out in Brazil and in the world?
Miranda - Many conservation programs in Brazil are very interesting and deserve attention, but two are worth of mentioning here. The first one, the reintroduction of tortoises in the Atlantic Forest, aims to restore ecological interactions of seed dispersal, led by researchers such as Carolina Starling.
Another admirable initiative is the Cropan’s Boa (Corallus cropanii) conservation program, led by Bruno Rocha, in São Paulo. His team found, in 2017, the first living specimen of this species of snake in 64 years.
The Cropan’s Boa is a critically endangered species, studied by researchers who have few resources and lots of passion. It is surprising to know that this is the first and only initiative dedicated to this species endemic to Brazil.
The sustainable management of crocodilians in the Amazon, carried in Lago do Cuniã, in Rondônia state, and in Mamirauá, in Amazonas state, are also among initiatives that need to be replicated in Brazil.
Do you have any personal initiative on this subject?
Miranda - I am conducting the writing of a richly illustrated book focused exclusively on large reptiles that have been extinct by humans.
Among international examples, I am a great admirer of the conservation initiatives of the Cuban crocodile, and would like to see the species reintroduced in other islands of the Caribbean.
In the Indian Ocean, important conservation initiatives are directed at two endangered endemic malagasy tortoises. Two other giant tortoise species from Madagascar have been extinct in the last thousand years. In the Mauritius archipelago, another species of giant tortoise is being used to restore an entire ecosystem.
Which are the most threatened groups of large reptiles today?
Miranda - Large chelonians are particularly vulnerable because they can be easily captured and grow very slowly, both in terms of population and body size. Animals such as African spurred tortoises and Angonoka tortoises (Astrochelys yniphora) are functionally extinct in nature, but are found in large numbers in developed countries, where they are kept as pets. At another extreme, we have in China the Yangtze River turtle (Rafetus swinhoei), the largest freshwater turtle in the world, whose population today is restricted to two males and one female kept in captivity.
What would be, in your view, a good way to start changing the public perception of reptiles in Brazil?
Miranda - A Brazilian version of a BBC series such as "Life in Cold Blood", filmed in Brazilian ecosystems and featuring native animals, would be a great nature documentary and would do a beautiful service for the popularization of science and reptiles.
And in the academy?
Miranda - I think a well-formulated criticism, conveyed in the Brazilian academy's traditional media ( scientific journals), could serve to open our researchers’ eyes to the tremendous gap in our knowledge about the ecological role of large reptiles. Do not get me wrong: national herpetology has made remarkable strides in the demographics of crocodilians, in the conservation of Amazonian tortoises, in the study of lizard evolution and many other areas. But we are still lagging behind on certain topics.
What about non-governmental organizations?
Miranda - Given the few resources available to these institutions, I already see great progress in their actions, such as the excellent program of conservation of Amazonian chelonians directed by the Wildlife Conservation Society. NGOs could also participate more actively in the management of several species of reptiles with potential for sustainable use in Brazil, extending the current management of caimans, and replicating it to chelonians and snakes. The sustainable use of these species for the production of meat, leather and derivatives can greatly contribute to their conservation by replacing the unsustainable poaching that occurs today.
And in the various governmental spheres?
Miranda - Government and academia need to learn to exchange information more closely. Today both act as two independent echo chambers with little ability to change the destiny of large reptile species. This deficiency has been repeatedly demonstrated by researchers in Brazil and other developing countries. Our main reptile research bodies focus on the conservation of organisms, but generally lose sight of the fact that a very subtle type of loss comes before extinction: the loss of ecological interactions.
In addition, conservation agenda priorities in Brazil are still dominated by charismatic wildlife. Cryptic species such as the Cropan’s Boa and the Hoge turtle (Mesoclemys hoge) are at the hands of few researchers and conservationists that work hard but are underfunded.
In conclusion, what message would you like to leave to the readers of this interview?
Miranda - The low charisma of reptiles has clearly been one of the greatest challenges in the struggle for its conservation. They are popularly held as dimwitted, insipid or cruel, "cold-blooded" animals. Among biologists and other environmental professionals, the general view is that reptiles are an evolutionary dead end, lacking everything that birds and mammals have. Stepping outside the perspective of intelligent, "warm-blooded" mammals can help us appreciate the millions of solutions that the evolutionary process has encountered for the challenge of existence. An enormous diversity of such evolutionary solutions can be found among large reptiles.
Our irresponsibility has led us to overuse many of these extraordinary beasts, in many cases terminally. Several of these species are known as piles of bone transformed into rock and remain alive only in the imagination of some curious, crazy people and few scientists. Today, the last elements of this once abundant group of giant reptiles are threatened, as are the ecological processes promoted by them. It is our duty to ensure that they remain alive outside our imagination.
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Everton Miranda
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