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... Our understanding of the biology of adult Green Anacondas has improved in recent years. There have been comprehensive studies of their mating system (Rivas and Burghardt, 2001;Rivas et al., 2007a), general natural history (Rivas, 2000;Rivas et al., 2007b), conservation and sustainable use (Rivas, 2007(Rivas, , 2010, predation (Rivas et al., 1999Rivas and Owens, 2000), diseases (Calle et al., 1994, foraging (Rivas, 1998(Rivas, , 2004, and demography (Rivas and Corey, 2008), along with notes on field techniques (Rivas et al., 1995;Raphael et al., 1996;Rivas, 2008). Adult anacondas live in shallow, stagnant water that is often covered by aquatic vegetation (Rivas, 2000;Rivas et al., 2007b). ...
... Average prey size observed in neonates is on par with the expected prey size found in adult snakes (Greene, 1992;Sazima, 1992), and it is not uncommon for large constrictors (Branch and Haacke, 1980;Rivas, 1998Rivas, , 2000Shine et al., 1998). Andreadis and Burghardt (2005) reported that neonatal Northern Water Snakes (Nerodia sipedon), given the choice, chose meal sizes close to 25% of their body mass. ...
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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 Anacondas from opportunistic captures in the wild over a 17-year period, as well as from a brief study on captive-born radio-tagged individuals. Both approaches converge in presenting a picture of the ecology of neonatal anacondas showing many similarities between their natural history and that of adult anacondas in spite of the great size difference. The neonates' biology resembles that of adults, especially males, in their preference for birds in their diet, the relative prey size they choose, slow growth rates they experience, low feeding frequency, little mobility, and preference for similar habitats of stagnant, shallow water covered by aquatic vegetation. The conventional wisdom that neonatal reptiles are replicates of their adult counterparts seems to be largely on target in Green Anacondas. © 2016 by the American Society of Ichthyologists and Herpetologists.
... Lack of documentation may be due to low human population density in areas where anacondas are common, and to the nature of their behavior and the habitat where they live. Here I document predatory strikes by green anacondas on two of my field assistants (Rivas 1998). The first attempt was by a large female (Lina; 54 kg, 5.04 m total length) that had had a serious mouth infection at the time I captured it and implanted a radiotransmitter. ...
... After parturition, the females often look very weak and thin, and may be more likely to be predated (Chapter 3;). Animals in this condition may attack larger, more dangerous prey in order to overcome their energetic deficit, taking the risk of been injured or even killed by their prey (Chapter 3; Rivas 1998). Anacondas give birth at the end of the wet season. ...
Thesis
Thesis (Ph. D.)--University of Tennessee, Knoxville, 2000. Vita. Includes bibliographical references (leaves 267-284).
... Green anacondas feed mostly on small to medium-sized mammals but may occasionally prey on larger mammals such as deer ( Kolesnikovas et al., 2007;Puorto and França, 2009). Because of their large size (up to 10m snout-vent-length [SVL]), green anacondas can pose dangers to humans (Rivas, 1998). Boa constrictor constrictor is commonly found in dry and mesic habits in Brazil. ...
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Boids are large, constrictor snakes that feed mostly on mammals, reptiles, and birds. These animals are commonly raised as pets, and their improper handling can favor the emergence of fungal infections, which can lead to dermatological diseases that are undiagnosed in nature. Here, we isolate and identify the filamentous fungi that compose the mycobiota of the scales of boid snakes kept in captivity at the Biological Museum of the Butantan Institute. Thirty individuals of four species were evaluated: four Eunectes murinus, twelve Boa constrictor constrictor, seven Corallus hortulanus, and seven Epicrates crassus. Microbiological samples were collected by rubbing small square carpets on the snake scales. We isolated five genera of fungi: Penicillium sp. (30%), Aspergillus sp. (25%), Mucor sp. (25%), Acremonium sp. (10%), and Scopulariopsis sp. (10%). Approximately half of the snakes evaluated had filamentous fungi on the scales, but only 12% of the individuals were colonized by more than one fungal genus. We found no dermatophytes in the evaluated species. Our results provide an overview of the fungal mycobiota of the population of boids kept in the Biological Museum, allowing the identification of possible pathogens.
... al. (2008), Lamonica et. al. (2007), Müller (1970), Petzold (1983) Rivas (1998, 2000, Rivas and Corey (2008), Rivas and Burghardt (2001), Rivas and Owens (2000), Rivas et. al. (1995Rivas et. ...
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A review of the taxonomy of the New World boids finds several genera as currently recognized to be paraphyletic. There are available genus names for those species within genera that have been found to be composite, should they be split to ensure monophyletic genera. The only potential exception to this is within the genus Eunectes Wagler, 1830 as currently recognized. There is a strong argument in favor of splitting the so-called Yellow Anacondas away from the so-called Green Anacondas, at the genus level as a result of clear and consistent differences between the relevant taxa. This paper formalizes this division by taking a conservative position and naming and defining a new subgenus, Maxhoserboa subgen. nov. for the Yellow Anaconda and related species.
... Rivas (2000) described observations indicating that a male was highly selective, following the best females and disregarding animals of lower quality. This phenomenon has been seen in other snakes (Ford and Seigel, 1989;Madsen and Shine, 1992, 1998Brown and Shine, 2005), and appears to be a consistent trend when we analyze the available body of data (Rivas and Burghardt, 2005). ...
... All 5 incidents occurred in flooded vegetation communities. Possibly predatory attacks on biologists by green anacondas (Eunectes murinus) in flooded environments in Venezuela were also reported by Rívas (1999). As humans wade through shallow water, they produce ripples that move ahead of them, and these pressure waves may be detectable to a motionless snake in ambush posture. ...
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Invasive Burmese pythons (Python molurus bivittatus) are now established across a large area of southern Florida, USA, including all of Everglades National Park (NP). The presence of these large-bodied snakes in the continental United States has attracted intense media attention, including regular reference to the possibility of these snakes preying on humans. Over the course of a decade (2003–2012), we solicited reports of apparently unprovoked strikes directed at humans in Everglades NP. We summarize the circumstances surrounding each of the 5 reported incidents, which occurred between 2006 and 2012. All strikes were directed toward biologists moving through flooded wetlands; 2 strikes resulted in minor injury and none resulted in constriction. We consider most of these strikes to be cases of "mistaken identity," in which the python initiated a strike at a potential prey item but aborted its predatory behavior prior to constriction and ingestion. No strikes are known to have been directed at park visitors despite visitation rates averaging over one million per year during this period. We conclude that while risks to humans should not be completely discounted, the relative risk of a human being killed by a python in Everglades NP appears to be extremely low. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. KEY WORDS Burmese pythons, Everglades, Florida, human–wildlife interactions, invasive species, Python molurus bivittatus.
... Adverse impacts associated with potentially invasive species Several species identified by our models as potential invaders are capable of causing harm to humans and domestic animals and adverse ecological impacts. Fatal attacks on humans, livestock, and pets by large or venomous snakes, such as P. sebae, M. amethistina, E. murinus, and B. arietans, were reported in their native range (Branch and Hacke 1980;Rivas 1998;Luiselli et al. 2001;Spawls et al. 2002;Mallow et al. 2003). Notably, a large number of these species (nearly or more than 1,000 animals of each species from 2000 to 2005) were imported through Miami and St. Petersburg ports. ...
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The recent explosion of exotic reptiles in south Florida requires effective management strategies. The objective of this study is to bring knowledge of ecological correlates and quantitative modeling methods into management by providing the foundation for a screening procedure that will identify potentially invasive species and assess adverse impacts associated with these species. We considered 17 variables and, based on model selection procedures, we identified the following significant predictors of establishment success: taxonomic order, maximum temperature match between a species’ native range and Florida, animal sale price, and manageability (defined as a species’ maintenance cost, aggressiveness, proneness to escape, and venomousness). Applying the models to predict establishment success of 33 reptiles that were most frequently imported through Miami and St. Petersburg ports from 2000 to 2005 and two additional reptiles of concern in Florida, we identified eight lizards and four snakes as potentially successful invaders. We further assessed adverse impacts associated with potential invaders, should they become established, by identifying species that are (1) dangerous to humans, (2) dangerous to the ecosystem (upper trophic-level predators), and (3) rapidly spreading. Controlling exotic reptiles can be expensive and labor intensive once they are established. Information on which species are potential invaders based on screening procedures and what impacts these species might cause will be a valuable contribution to the development of proactive management strategies. KeywordsClimate match-Establishment-Exotic species-Prediction
... Body mass data even for living snakes is hard to come by (Ernst and Zug 1996). A big female E. murinus, 5.04 m in length, is recorded as being 54 kg by Rivas (1999). No complete skull is known for W. naracoortensis. ...
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The notion that Australia's large, terrestrial carnivore faunas of the middle Tertiary to Pleistocene were dominated by reptiles has gained wide acceptance in recent decades. Simple but sweeping hypotheses have been developed seeking to explain this perceived ecological phenomenon. However, a review of the literature does not support these interpretations, which are based on largely speculative and, in many cases, clearly erroneous assumptions. Few size estimates of fossil reptilian taxa are based on quantitative methodology and, regardless of method, most are restricted to maximum dimensions. For species of indeterminate growth, this practice generates misleading perceptions of biological significance. In addition to misconceptions with respect to size, much speculation concerning the lifestyles of large extinct reptiles has been represented as fact. In reality, it has yet to be demonstrated that the majority of fossil reptiles underpinning the story of reptilian domination were actually terrestrial. No postcranial evidence suggests that any Australian mekosuchine crocodylian was less aquatic than extant species, while a semi-aquatic habitus has been posited for madtsoiid snakes and even the giant varanid, Megalania. Taphonomic data equivocally supports the hypothesis that some Australian mekosuchines were better adapted to life on land than are most extant crocodylians, but still semi-aquatic and restricted to the near vicinity of major watercourses. On the other hand, the accelerating pace of discovery of new large mammalian carnivore species has undermined any prima facie case for reptilian supremacy regarding pre-Pleistocene Australia (that is, if species richness is to be used as a gauge of overall impact). However, species abundance and consumption, not richness, are the real measures. On this basis, even in Pleistocene Australia, where species richness of large mammalian carnivores was relatively low, available data expose the uncommon and geographically restricted large contemporaneous reptiles as bit players. In short, the parable of a continent subject to a Mesozoic rerun, wherein diminutive mammals trembled under the footfalls of a menagerie of gigantic ectotherms, appears to be a castle in the air. However, there may be substance to some assertions. Traditionally, erratic climate and soil-nutrient deficiency have been invoked to explain the perception of low numbers or relatively small sizes of fossil mammalian carnivore taxa in Australia. But these arguments assume a simple and positive relationship between productivity, species richness and maximum body mass and either fail to recognise, or inappropriately exclude, other factors. Productivity has undoubtedly played a role, but mono-factorial paradigms cannot account for varying species richness and body mass among Australia's fossil faunas. Nor can they explain differences between Australian fossil faunas and those of other landmasses. Other factors that have contributed include sampling bias, a lack of internal geographic barriers, competition with large terrestrial birds and aspects of island biogeography unique to Australia, such as landmass area and isolation, both temporal and geographic. ZO010 53 S. W ro e Eco lo gy of Au s tr al ia n fos s il ca rn ivor es
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We here revisit the natural history of Green Anacondas and give our personal view of how Ecotourism can affect their existence.
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