Population Density and Survival Estimates of the African Viperid, Bitis schneideri

Maritz, Bryan; Alexander, Graham J.

doi:10.1655/herpetologica-d-11-00043.1

Cited by 14 publications

(22 citation statements)

References 26 publications

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“…() suggested that the maturity age of Bothrops species is around 1.5–3 years. While it is hard to estimate the annual survival rate of these snakes over time, which probably vary with climatic conditions and food supply, some data for populations of Crotalinae species suggest annual survival rates around 0.39 to 0.77 (Brown, Kéry, & Hines, ; Maritz & Alexander, ). Based on these data, we estimate generation times in Bothrops bilineatus as being around 2–3 years.…”

Section: Methodsmentioning

confidence: 99%

Phylogeography and historical demography of the arboreal pit viper Bothrops bilineatus (Serpentes, Crotalinae) reveal multiple connections between Amazonian and Atlantic rain forests

Vechio

Prates

Grazziotin

et al. 2018

Journal of Biogeography

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Aim To examine historical connections between rain forest habitats in the Neotropics based on the evolutionary history of the arboreal pit viper Bothrops bilineatus. Location Amazonia and Atlantic Forest in South America. Methods We inferred phylogenetic relationships within Bothrops and phylogeographic relationships within B. bilineatus using both concatenated and species tree approaches under a Bayesian framework based on four mitochondrial and five nuclear genes. We inferred demographic history within B. bilineatus based on tests of alternative historical scenarios using coalescent simulations and Approximate Bayesian Computation. Results Phylogenetic analyses recovered four major clades within Bothrops bilineatus. The best‐fit historical scenario involved colonization of the Atlantic Forest by an Amazonian ancestor around 2 Mya, followed by range expansion in the Atlantic Forest. Subsequently, there was a colonization event into the Guiana Shield from an Atlantic Forest ancestor, dating back to around 0.3 Mya. Main conclusion The complex demographic history of Bothrops bilineatus shows multiple connection events between Amazonia and the Atlantic Forest in the last 2 million years. Two previously hypothesized forest bridges, southern and northeastern, may have been involved in range expansions in this species. These results shed light on the historical processes involved in the diversification of this venomous South American snake, providing information about the historical dynamism of forested habitats in the Neotropics.

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Section: Methodsmentioning

confidence: 99%

Phylogeography and historical demography of the arboreal pit viper Bothrops bilineatus (Serpentes, Crotalinae) reveal multiple connections between Amazonian and Atlantic rain forests

Vechio

Prates

Grazziotin

et al. 2018

Journal of Biogeography

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“…Our measures of meandering in Namaqua dwarf adders are low (Secor 1994 reports meander ratio, the inverse of the straightness index, of >2:1 for Crotalus cerastes, corresponding to a straightness index of >0.5), and are in keeping with those expected for an ambush forager moving from one location to another. We recorded significantly more meandering (lower straightness index) in juveniles, possibly due to an increased need for juveniles to avoid exposure to thermal radiation and possibly accounting for the lower detection probabilities recorded by Maritz & Alexander (2012b). Although Secor (1994) found lower meander ratios for neonate C. cerastes, he did not find differences between juveniles and adults.…”

Section: Discussionmentioning

confidence: 61%

“…Individuals move from one lie‐up position to another with relatively short displacements (

\overset{normalx}{true}

: 6.5 m; range: 1–54 m; N = 192), although animals travel further (

\overset{normalx}{true}

: 45.0 m; range: 1–277 m; N = 166) during spring (based on raw data used in Maritz & Alexander ). Namaqua dwarf adders occupy relatively small home ranges (typically 0.1–1 ha; Maritz & Alexander ) that exhibit both sex‐based and seasonal variation in size. The limited movement displayed by the snakes is likely to be at least partly induced by risk of predation as populations experience high annual mortality rates (

\overset{normalx}{true}

: ≈50%; range: 44–61%; Maritz & Alexander ) and their predators are diverse and abundant (Maritz & Scott ).…”

Section: Methodsmentioning

confidence: 99%

“…Namaqua dwarf adders occupy relatively small home ranges (typically 0.1–1 ha; Maritz & Alexander ) that exhibit both sex‐based and seasonal variation in size. The limited movement displayed by the snakes is likely to be at least partly induced by risk of predation as populations experience high annual mortality rates (

\overset{normalx}{true}

: ≈50%; range: 44–61%; Maritz & Alexander ) and their predators are diverse and abundant (Maritz & Scott ). Prolonged exposure also has thermoregulatory consequences, especially in arid environments where solar radiation is intense and surface temperatures can be extreme.…”

Section: Methodsmentioning

confidence: 99%

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Scale‐dependent Orientation in Movement Paths: A Case Study of an African Viper

Maritz

Alexander

2015

Ethology

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Decisions relating to the orientation of movement by animals and how this translates into movement patterns can occur at multiple spatial scales simultaneously, but this interaction is poorly understood for many groups of animals. Using the tracks left by moving snakes in their sandy habitat, we studied the movement paths of the African snake Bitis schneideri (Namaqua dwarf adder) for evidence of broad-scale directional persistence and short-range avoidance of exposure. Although snakes clearly displayed directional persistence, they preferentially moved to nearby shrubs, thereby minimizing exposure to solar and thermal radiation and/or predation. Thus, snakes made decisions relating to orientation at a minimum of two scales, the interaction of which resulted in snakes moving %17% (mean straightness index = 0.85) further than the simple broad-scale straight-line distance. We assert that the actual path chosen by moving snakes represents a trade-off of various costs and risks that include risk of predation, exposure to the elements, time and energy expenditure. Our study highlights the need for cognizance of the possibility of the scale dependence of orientation and movement in studies of snake movement, and adds to a growing literature demonstrating previously unrecognized behavioural complexity in snakes.

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“…) demonstrates that biennial reproduction is possible in B. schneideri ( n < 0.6 litters yr −1 ). However, for a population to persist for extended periods of time under these conditions, the population needs to concurrently experience survival rates that are higher than we have measured (Maritz & Alexander, ). Thus, periods of reduced frequency of reproduction resulting from reduced prey availability can only be sustained if there is a concomitant increase in survival.…”

Section: Discussionmentioning

confidence: 89%

Namaqua dwarf adders must breed frequently: the problem with being small

Maritz

Alexander

2012

Journal of Zoology

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Reproductive frequency is a key component of reproductive output, and has important influences on organismal fitness and population persistence. Viperid snakes, like many other ectothermic vertebrates, generally exhibit a low frequency of reproduction (LFR), as females only reproduce every second year, or even less frequently. However, for small‐bodied species with constrained clutch/litter sizes, and low survival, reproductive frequency cannot be too infrequent if populations are to persist. We assessed whether Bitis schneideri, a small, arid‐adapted viperid snake from southern Africa has the LFR typical of many other viperids, despite having low survival and small litters. We calculated the reproductive frequency required to sustain a population using information gathered from recent studies of the ecology of the species. The small litter size imposed by being small‐bodied, and low annual survival, require B. schneideri to reproduce frequently, probably annually, for populations to persist. We also assessed the reproductive status of all available preserved adult females. A high proportion were reproductive (up to 80% during summer), with developing or mature follicles, or developing young. Such frequent reproduction is atypical, even among closely related species, and might be facilitated through the capacity of B. schneideri to feed year‐round in the aseasonal habitat in which it occurs. We predict that future studies of small‐bodied species from climates that allow for extended periods of feeding will continue to show that frequent reproduction is more widespread among vipers than is currently assumed.

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Population Density and Survival Estimates of the African Viperid, Bitis schneideri

Cited by 14 publications

References 26 publications

Phylogeography and historical demography of the arboreal pit viper Bothrops bilineatus (Serpentes, Crotalinae) reveal multiple connections between Amazonian and Atlantic rain forests

Phylogeography and historical demography of the arboreal pit viper Bothrops bilineatus (Serpentes, Crotalinae) reveal multiple connections between Amazonian and Atlantic rain forests

Scale‐dependent Orientation in Movement Paths: A Case Study of an African Viper

Namaqua dwarf adders must breed frequently: the problem with being small

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