Article

# Home range and habitat use of Beni anacondas (Eunectes beniensis) in Bolivia

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## Abstract

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.

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... The Beni anaconda, Eunectes beniensis, is a largesized aquatic Boid snake, usually attaining up to 2 m, and endemic to the floodplains of the Bolivian Amazonia (Quintana et al., 2017). The Bolivian river dolphins, Inia boliviensis, are large-sized freshwater mammals, that reach up to 2.4 m, and are also endemic to the floodplains of Bolivian Amazonia (Aliaga-Rossel & Escobar, 2020; Guizada & Aliaga-Rossel, 2016). ...
... Due to their larger size, adult anacondas will often have few or no natural predators (Rivas, 2000). However, it should be noted that the Beni anaconda is likely one of the smallest species of its genus, often attaining a smaller size (mean SVL [snout-vent length] = 1.92 m; Quintana et al., 2017) than its other counterparts, such as the Green anaconda, Eunectes murinus (Linnaeus, 1758), which attains up to 6 m (mean SVL = 3.7 m; Rivas, 2000) (Haddad-Junior, 2012Rivas, 2000), or the Yellow anaconda, Eunectes notaeus Cope, 1862, which attains up to 3.3 m (mean female SVL = 2.1 m; Waller et al., 2007). This smaller size could likely cause the Beni anaconda to be more vulnerable to predators. ...
... We used the reference smoothing parameter (href) to run the fixed kernel mehod. We edited the maps using the ArcGIS 10.3 software (ESRI 2015) and visualised them on satellite images using Google Earth Pro (Wasko & Sasa 2010;De la Quintana et al. 2017). ...
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... Understanding how home ranges are arranged in the landscape helps us to identify the most important habitat traits influencing the ecology of a given species (Powell 2000). For example, we can study which habitat traits lead individuals to select or avoid a certain place (Sung et al. 2015;De la Quintana et al. 2017). Besides, assessing the degree of overlap between home ranges could reveal mating sys-them with multiple males (Harless et al. 2009;Bower et al. 2012). ...
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Studying how different variables influence the size and shape of animals’ home ranges helps our understanding of the ecology of individuals and populations. This study aims to assess the effects of sex and body mass on home range size and the sexual differences in the use of terrestrial habitats of a population of aquatic turtles Phrynops geoffroanus from an urban area in Mato Grosso do Sul, Brazil. Turtles were captured along a river by active search, occasional encounter and hoop traps. Using individual VHF radio transmitters, 13 individuals (7 females and 6 males) were radio-tracked by homing in on the signal strength of the transmitter. Home ranges were estimated by 95% and 50% core one-dimensional fixed kernel and linear distance method. Home ranges were similar for both sexes (t = -0.50, DF = 12, p = 0.62) and independent of body mass (t = -0.53, DF = 12, p = 0.60). However, females seemed to use terrestrial habitats more than males (females = six recorded locations out of 767 points; males = none), probably to nest. To gain insight on how males and females use their space, it would be useful to focus future studies on the influence of sex in microhabitat selection of Phrynops geoffroanus. Finally, as sex did not influence home range, studying the contribution of other variables – both intrinsic, as age or personality, and extrinsic, as habitat composition or distribution of trophic resources – shaping the home ranges of the species is proposed.
... Understanding how home ranges are arranged in the landscape helps us to identify the most important habitat traits influencing the ecology of a given species (Powell 2000). For example, we can study which habitat traits lead individuals to select or avoid a certain place (Sung et al. 2015;De la Quintana et al. 2017). Besides, assessing the degree of overlap between home ranges could reveal mating sys-them with multiple males (Harless et al. 2009;Bower et al. 2012). ...
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Studying how different variables influence the size and shape of animals’ home ranges helps our understanding of the ecology of individuals and populations. This study aims to assess the effects of sex and body mass on home range size and the sexual differences in the use of terrestrial habitats of a population of aquatic turtles Phrynops geoffroanus from an urban area in Mato Grosso do Sul, Brazil. Turtles were captured along a river by active search, occasional encounter and hoop traps. Using individual VHF radio transmitters, 13 individuals (7 females and 6 males) were radio-tracked by homing in on the signal strength of the transmitter. Home ranges were estimated by 95% and 50% core one-dimensional fixed kernel and linear distance method. Home ranges were similar for both sexes (t = -0.50, DF = 12, p = 0.62) and independent of body mass (t = -0.53, DF = 12, p = 0.60). However, females seemed to use terrestrial habitats more than males (females = six recorded locations out of 767 points; males = none), probably to nest. To gain insight on how males and females use their space, it would be useful to focus future studies on the influence of sex in microhabitat selection of Phrynops geoffroanus . Finally, as sex did not influence home range, studying the contribution of other variables – both intrinsic, as age or personality, and extrinsic, as habitat composition or distribution of trophic resources – shaping the home ranges of the species is proposed.
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Thesis (Ph. D.)--University of Tennessee, Knoxville, 2000. Vita. Includes bibliographical references (leaves 267-284).
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Resting metabolic rates (RMR) of 34 species from 18 genera of boas and pythons (Serpentes: Boidae), with body masses ranging from 2 to 67,800 g, were determined as oxygen consumption ($$\dot V_{O_2 }$$) and carbon dioxide production ($$\dot V_{CO_2 }$$) at three ambient temperatures (T a). The temperature coefficient of metabolism (Q10) averaged 2.61 betweenT a of 20–30°C and 2.65 between 30 and 34°C. The respiratory exchange ratio RE (=$$\dot V_{CO_2 }$$/$$\dot V_{O_2 }$$) increased slightly with increasingT a (0.795 at 20°C, 0.819 at 30°C, and 0.834 at 34°C). Interspecific differences in Q10 and RE were slight or insignificant. A multiple regression relating metabolism ($$\dot V_{O_2 }$$) to mass andT a explained 97% of the variance in the pooled interspecific data. The mass exponent was 0.806, which is approximately the same as reported for squamates and for all reptilian taxa combined. The mean within-species slope (0.732) was significantly less than the slope for pooled data, but did not differ significantly from 0.75. In 40 of 42 cases (14 species at 3T a), within-species slopes did not differ from each other. Values of the adjusted mean Y, from covariance analysis, were significantly and positively correlated with mass, indicating that the mass coefficient increases with increasing mass. Considerable variation in metabolic rate is apparent both within and between ecological and taxonomic categories.
• L Dirksen
• W Böhme
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A safe method for handling large snakes in the field
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Nyao ito: Caza y Pesca de los Sirionó
• W Townsend
Townsend, W. (1996): Nyao ito: Caza y Pesca de los Sirionó. Instituto de Ecología, Universidad Mayor de San Andrés, La Paz.
Reptiles Eunectes beniensis, Dirksen (2002): Squamata-Boidae
• Embert
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• R M Andrews