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Home range and habitat use of Beni anacondas (Eunectes beniensis) in Bolivia
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.
... 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). ...
This is the first multiple months study on home range and habitat use by a small group of bushmaster (Lachesis spp.). Five snakes (natives and translocated) were intensively radio tracked in a mosaic of plantations and small fragments of Atlantic Forest in the Reserva Ecologica Michelin in Bahia, Brazil. The average home range was 9.47 ha (MCP 95%) and 44.11 (Kernel 95%) for bushmasters tracked for more than 6 months. The macrohabitats used were primarily composed of disturbed primary (partially logged) and secondary (originally cleared) forests, but also of rubber tree plantations with a dense understory vegetation. Activity centres were closer to the forest edge (~ 22 m) than the core of the small forest fragments. The snakes mainly occupied wooded microhabitats with complex vegetation structures, around 50% under- and mid-story cover. Nocturnal ambush differed from diurnal resting microhabitats on the surface mainly by being significantly closer to mammal trails and a more open understory space. While mammal burrows and refuges under roots and rocks have been used, diurnal resting was primarily on the forest floor (75%). Translocation from sites > 20 km outside the study site has produced little evidence of negative effect, as all individuals grew impressively, continued an apparently normal life and established a home range similar to native bushmasters.
... 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). ...
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). ...
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.
Opportunistic finding of anacondas preying on co-specifics.
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.
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
Modern ecological research often involves the comparison of the usage of habitat types or food items to the availability of those resources to the animal. Widely used methods of determining preference from measurements of usage and availability depend critically on the array of components that the researcher, often with a degree of arbitrariness, deems available to the animal. This paper proposes a new method, based on ranks of components by usage and by availability. A virtue of the rank procedure is that it provides comparable results whether a questionable component is included or excluded from consideration. Statistical tests of significance are given for the method. The paper also offers a hierarchical ordering of selection processes. This hierarchy resolves certain inconsistencies among studies of selection and is compatible with the analytic technique offered in this paper.
Miniature radio transmitters were surgically implanted in 15 adult diamond pythons from two areas
near Sydney, N.S.W., in south-eastern Australia, and the snakes monitored for intervals of 4-32
months. We document patterns of habitat use and movements, and interpret these in terms of the
feeding habits and reproductive biology of the pythons. These snakes were usually sedentary in summer
and autumn, with occasional long movements to new sites. During spring (the mating season), males
moved long distances, often daily. Telemetered pythons were generally diurnal and terrestrial rather than
arboreal. Snakes were most commonly recorded coiled under vegetation which provided filtering cover
(34% of locations). The relative use of different habitats by diamond pythons changed with season.
In summer and autumn, snakes were most frequently in disturbed habitats (such as areas around
houses), where prey are relatively common. In winter the snakes used rocky habitats, especially
sandstone crevices. No winter aggregations were observed. The radio-tracked snakes had large (up
to 124 ha), well-defined but overlapping home ranges, and these varied significantly between sexes and
among seasons. Detailed analysis of python movements shows that at least two assumptions of many
home-range analyses (normally distributed data and adequacy of small sample sizes) are invalid for
our study.
Kernel home-range estimators are becoming more widely used to determine the home-range size for herpetofauna, despite the problems associated with selecting the appropriate smoothing factor. We used simulations to demonstrate the inconsistency of kernel estimators at determining the home-range size of random distributions. Furthermore, we used the positions of ten adult male Lampropeltis triangulum radiotracked over two full active seasons (2003 and 2004) to demonstrate that the size of the home range increases significantly with an increase in the smoothing factor. The degree of increase, however, was not consistent between individuals. In addition, using least-squares cross-validation to select the smoothing factor produced a wide range of values for different individuals. Because of these inconsistencies, we suggest using the minimum convex polygon (MCP) method to calculate home-range size in studies of herpetofauna. When studying habitat use, however, we suggest using the MCP as the area of the home range and adjusting the smoothing factor until the area of the 95% kernel equals the area of the MCP. This provides an objective method for selecting the smoothing factor.
Many statistical procedures and metrics have been developed to analyze animal home-range data. We evaluated a point peeling method that may be useful in the analysis of such data. Our objectives were to 1) identify an appropriate peeling criterion that performs well across the suite of underlying behaviors, and 2) compare sample and expected utilization distribution (UD) curves as the basis of a procedure for classifying animal behavior. We addressed the first objective by comparing 3 peeling criteria: 1) peeling farthest from the sample centroid, 2) peeling farthest from the harmonic mean, and 3) peeling the location that caused the greatest decrease in area of remaining data. We compared these criteria across 5 different biologically plausible home-range behaviors as represented by 5 idealized statistical distributions. Comparison of expected UD curves and those generated from simulated data revealed several important considerations: 1) the centroid peeler offered the most accurate and consistent results, 2) the harmonic mean peeler exhibited particularly large amounts of variability, and 3) the area peeler was not able to consistently identify distributions representing clustered or territorial behavior. We addressed the second objective by comparing sample curves to expected UD curves using the centroid peeler. Results revealed each of the sample UD curves captured the key features of the underlying statistical distribution and hence, when dealing with real samples, the behavior. Further, in several examples, the UD curves identified underlying distributions that were not apparent by visual inspection. Overall, point peeling using the centroid peeling function provided a simple but robust procedure for field biologists that made good use of all the data from a sample. This procedure provided an objective home-range measure and a way of classifying home-range use.
Observations of foraging behavior of the Puerto Rican boa (Epicrates inornatus) were per-formed at a cave entrance beginning one hour before sunset until one hour after sunrise. Boas captured bats from 1745 h to 0600 h, but most captures were between 1900 and 2400 h. The most common preyed bats were Erophylla sezekorni, Mormoops blainivillii, Pteronotus quadridens and Monophyllus redmanii, while Brachy-phylla cavernarum was rarely caught. The average prey handling time was 12.53 min. The Radiotelemetry was used to determine the home range, activity and movements of E. inornatus. Eleven snakes (six females and five males) were fitted with transmitters. Using the minimum convex polygon method, the average home range area for females and males was 7,890 m 2 ± 6614 m 2 and 5,000 m 2 ± 4,102 m 2 , respectively. These were not significantly different. Ten of the radio-tracked snakes returned at least twice to the cave. Females were active during 29 ± 7.2% (n = 89) of the observations, and the males were 36 ± 12.5% (n = 66). Movement by E. inornatus has notable implications for surveys and site assessment. Sites should be managed to ensure that all features needed by the species are available within relatively discrete patches; thus, feeding and ther-moregulatory requirements and the provision of shelter and protection should all be available within a limited area.
Abstract No consensus currently exists for the methods of estimation of home range size or for reporting home-range analysis results. Studies currently employ a variety of disparate methods or provide inadequate information for reproducing their analyses. We reviewed 161 home range studies published in 2004, 2005, and 2006 to assess what methods are currently employed and how results are reported. We found that home range reporting was generally inadequate for reproducing studies; that the methods employed varied considerably; that home range estimates were often reported and analyzed using inappropriate methods; and that many comparisons were made between studies that may produce spurious results. We urge for minimum editorial standards for reporting home range studies and we urge researchers to follow a unified methodology for estimating animal home ranges. We supply recommendations for such reporting and methodology. These recommendations will increase the reproducibility of studies and allow for more robust comparisons between studies.
Yellow anacondas (Eunectes notaeus) are large, semiaquatic boid snakes found in wetland systems in South America. These snakes are commercially harvested under a sustainable management plan in Argentina, so information regarding population structuring can be helpful for determination of management units. We evaluated genetic structure and migration using partial sequences from the mitochondrial control region and mitochondrial genes cyt-b and ND4 for 183 samples collected within northern Argentina. A group of landscape features and environmental variables including several treatments of temperature and precipitation were explored as potential drivers of observed genetic patterns. We found significant population structure between most putative population comparisons and bidirectional but asymmetric migration in several cases. The configuration of rivers and wetlands was found to be significantly associated with yellow anaconda population structure (IBD), and important for gene flow, although genetic distances were not significantly correlated with the environmental variables used here. More in-depth analyses of environmental data may be needed to fully understand the importance of environmental conditions on population structure and migration. These analyses indicate that our putative populations are demographically distinct and should be treated as such in Argentina's management plan for the harvesting of yellow anacondas.
A statistical technique evaluating preference or avoidance of a given habitat or forage species is presented, using moose (Alces alces) distribution patterns in an area including the Little Sioux Burn of northeastern Minnesota as an example. The technique is used in conjunction with a chi-square analysis, after the chi-square has led to the rejection of the null hypothesis that a set of observations follows an "expected" occurrence pattern. The technique involves the use of a Bonferroni z statistic which may be used in estimating whether a specific observation occurs more or less frequently than expected. The technique provides a refinement of quantitative methods which heretofore have not been used to test a multinomial distribution applicable to the example.
Entre los años 2002 y 2004 se llevó a cabo en la provincia de Formosa la etapa experimental piloto (EEP) del "Progra- ma para la conservación y el aprovechamiento sustentable de la boa curiyú (Eunectes notaeus) en la Argentina". La EEP tuvo como objetivos profundizar los estudios de biología reproductiva e historia natural de la boa curiyú, estable- cer pautas experimentales de manejo y fiscalización, así como analizar las características ecológicas y económicas de la producción. En los tres años se obtuvieron un total de 16.517 cueros con una media de 2,6 m de longitud, y valo- res de CPUE y rendimiento constantes. De esta manera, comenzaron los registros y mediciones de indicadores de abundancia y sustentabilidad de una especie con un gran vacío previo de información, y para una población con nin- guna o muy baja presión de caza reciente, pero que había sido intensamente explotada décadas atrás. En este capí- tulo presentaremos las bases y criterios para un plan de manejo y conservación de la especie, en acuerdo con los cri- terios de una administración adaptable. Palabras clave: administración adaptable, curiyú, Eunectes notaeus, Formosa, manejo sustentable. Resumen
[This corrects the article on p. e37473 in vol. 7.].
Summary • Kernel-density estimation (KDE) is one of the most widely used home-range estimators in ecology. The recommended implementation uses least squares cross-validation (LSCV) to calculate the smoothing factor (h) which has a considerable influence on the home-range estimate. • We tested the performance of least squares cross-validated kernel-density estimation (LSCV KDE) using data from global positioning system (GPS)-collared lions subsampled to simulate the effects of hypothetical radio-tracking strategies. • LSCV produced variable results and a 7% failure rate for fewer than 100 locations (n = 2069) and a 61% failure rate above 100 points (n = 1220). Patterns of failure and variation were not consistent among lions, reflecting different individual space use patterns. • Intensive use of core areas and site fidelity by animals caused LSCV to fail more often than anticipated from studies that used computer-simulated data. • LSCV failures at large sample sizes and variation at small sample sizes, limits the applicability of LSCV KDE to fewer situations than the literature suggests, and casts doubts over the method's reliability and comparability as a home-range estimator. Journal of Animal Ecology (2005) 74, 455 –463 doi: 10.1111/j.1365-2656.2005.00944.x
Thesis (Ph. D.)--University of Tennessee, Knoxville, 2000. Vita. Includes bibliographical references (leaves 267-284).
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.
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Final revision received
- Luca Luiselli
Submitted: May 2, 2017. Final revision received: August 15,
2017. Accepted: September 4, 2017.
Associate Editor: Luca Luiselli.
Studies on anacondas III. A reappraisal of Eunectes beniensis Dirksen, 2002, from Bolivia, and a key to the species of the genus Eunectes Wagler, 1830 (Serpentes: Boidae)
- Dirksen