1,721,004 research outputs found
Foraging ecology of Naja nivea and Dispholidus typus
Full text linkMagister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)It is widely reported that snakes can be major predators of avian nests, but the use of a single avian prey type by competing species has rarely been examined. This study aimed to investigate predation of a single food resource by the sympatric snakes Naja nivea and Dispholidus typus. Specifically, I aimed to 1) identify factors influencing snake presence in sociable weaver colonies and 2) quantify snake predation and potential differences in the consumption of prey by the two competing snakes.
I used repeated visual surveys of sociable weavers to obtain presence-absence data of cape cobra and boomslang in sociable weaver colonies over an entire breeding season. I related the presence-absence data of the two snake species to spatially- and temporally-variable factors using principal component analyses (PCA) and multiple logistic regression analyses. The presence of snakes in sociable weaver colonies is primarily influenced by temporal factors, but spatial factors also play a role
Quantifying competition in two co-occurring southern African psammophiinae snakes: Psammophis crucifer and psammophylax r. Rhombeatus
Full text linkMagister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)Studies on snake competitive interactions have relatively been well documented globally, however, those examples tend to be dominated by non-African examples. Africa has a large and spectacular reptile diversity and yet robust and empirical studies on snake population ecology remain poorly understood or documented. Given the close phylogenetic relationship between the two species, as well as the remarkable similarities in overall appearance, morphology, reproductive biology, and most importantly geographic distribution, Psammophis crucifer and Psammophylax rhombeatus offered an ideal study system in which to ask questions related to interspecific competition and niche partitioning
The diet and feeding ecology of the brown house snake, Boaedon capensis
Full text linkMasters of ScienceAfrican brown house snakes (Boaedon capensis) are widely thought to be dietary specialists
that predominantly consume rodents. Given their ubiquitous distribution, these snakes
potentially play an important role in controlling rodent populations throughout their range.
However, the full extent of the diet of this species remains poorly quantified, and the
proportional importance of mammals to their diet is speculative. Moreover, little is known
regarding intraspecific dietary variation of these snakes. In recent years, a dearth of reports of
B. capensis feeding, particularly from novel information-sharing streams available through
social media, suggests that the diet of these snakes may be broader than previously thought.
B. capensis are not rodent specialists as amphibians (3%), birds (12%), and reptiles (38%)
collectively comprise a significant proportion of their diet. There was no evidence for sexual
size dimorphism or dietary variation between adult males and females. However, significant
differences in morphology and prey utilisation between adults and juveniles indicate an
ontogenetic shift in diet from small lizards to larger, and more diverse prey. Variation in
climate and time of year did not affect diet. Importantly, the diet of B. capensis as presented
by museum data vastly differed compared to literature and community science reports. In
particular, the proportional use of reptiles differed across sources (museum data = 6%;
community science data = 27%). Overall, my findings reiterate the importance of examining
multiple sources of information when characterizing the diet of species, as these multiple
sources provide different result outcomes
Predicting reptile species distributions and biogeographic patterns within Kruger National Park
No full textMagister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)Knowledge of global reptile ecology is limited and there remains much to understand in terms of detailed reptile species information, including that of their distributions. In South Africa, despite being one of SANParks best-studied reserves, surprisingly little is known about the distributions and spatial ecology of reptiles within Kruger National Park (KNP). Management within KNP follows a strategic adaptive management strategy which monitors the statuses of animals using species or group specific indicators. Indicators are given predetermined upper and lower ranges of acceptable fluctuation before actions are taken. These ranges are referred to as thresholds of potential concern (TPCs), and for reptiles these are based on changes to their distributions across the landscape of KNP.
An apparent lack of high-quality reptile distribution data inhibits the effective monitoring of the statuses of these animals within KNP, which in turn limits management and conservation options. In this study, I use several methods to quantify available reptile occurrence data which formed the foundations for predicting the distributions of these species across KNP by means of species distribution modelling, with a view to gaining novel insight into reptile assemblage structure across the landscape of KNP
Predicting reptile species distributions and biogeographic patterns within Kruger National Park
Full text linkMagister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)Knowledge of global reptile ecology is limited and there remains much to understand in terms of detailed reptile species information, including that of their distributions. In South Africa, despite being one of SANParks best-studied reserves, surprisingly little is known about the distributions and spatial ecology of reptiles within Kruger National Park (KNP). Management within KNP follows a strategic adaptive management strategy which monitors the statuses of animals using species or group specific indicators. Indicators are given predetermined upper and lower ranges of acceptable fluctuation before actions are taken. These ranges are referred to as thresholds of potential concern (TPCs), and for reptiles these are based on changes to their distributions across the landscape of KNP.
An apparent lack of high-quality reptile distribution data inhibits the effective monitoring of the statuses of these animals within KNP, which in turn limits management and conservation options. In this study, I use several methods to quantify available reptile occurrence data which formed the foundations for predicting the distributions of these species across KNP by means of species distribution modelling, with a view to gaining novel insight into reptile assemblage structure across the landscape of KNP
Quantifying competition in two co-occurring southern African psammophiinae snakes: Psammophis crucifer and psammophylax r. Rhombeatus
No full textMagister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)Studies on snake competitive interactions have relatively been well documented globally, however, those examples tend to be dominated by non-African examples. Africa has a large and spectacular reptile diversity and yet robust and empirical studies on snake population ecology remain poorly understood or documented. Given the close phylogenetic relationship between the two species, as well as the remarkable similarities in overall appearance, morphology, reproductive biology, and most importantly geographic distribution, Psammophis crucifer and Psammophylax rhombeatus offered an ideal study system in which to ask questions related to interspecific competition and niche partitioning
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Functional importance of snakes in a strandveld ecosystem
No full textMagister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv & Cons Biol)Gaps in our knowledge of the functional roles of snakes within ecosystems limit our ability to
predict the potentially cascading effects their removal from an ecosystem might create.
Extirpation of snake species could potentially result in losses of ecosystem functionality if
those taxa are ecologically unique. I used pitfall and funnel trap arrays, artificial cover object
surveys, active searching, and passive camera trapping, as well as pre-existing faunal diversity
data to identify terrestrial tetrapod species within the Koeberg Private Nature Reserve. This
resulted in a list of 265 species, of which 13 were snakes. I then gathered data on dietary and
four additional functional traits for each species from the literature. Next, using hierarchical
and partitioning around medoids clustering, I identified ten broad dietary guilds and 54
functional guilds within the terrestrial tetrapod community. Of the dietary guilds Dasypeltis
scabra was the only snake species that formed a unique single species guild and was one of
four snake species (Pseudaspis cana, Homoroselaps lacteus and Lamprophis guttatus) to form
four unique single species functional guilds. The remaining snakes clustered together within
groups of other vertebrate predators. Functional diversity analysis was then used to simulate
losing eight major taxonomic groups (birds, passerines, non-passerines, mammals, reptiles,
snakes, non-snake reptiles and amphibians) and gauge the effects of those losses on overall
community dietary and functional diversity. Functional diversity analysis revealed that the loss
of certain snake species resulted in disproportionate losses of overall community dietary and
functional diversity while losing others had negligible effects. These findings provide
ambivalent support for the dietary and functional uniqueness of snakes suggesting that certain
snake species are fulfilling unique functional roles within the ecosystem. Additionally, it is
likely that losing those non-redundant species would result in significant losses of ecosystem
functionality
Foraging ecology of Naja nivea and Dispholidus typus
No full textMagister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)It is widely reported that snakes can be major predators of avian nests, but the use of a single avian prey type by competing species has rarely been examined. This study aimed to investigate predation of a single food resource by the sympatric snakes Naja nivea and Dispholidus typus. Specifically, I aimed to 1) identify factors influencing snake presence in sociable weaver colonies and 2) quantify snake predation and potential differences in the consumption of prey by the two competing snakes.
I used repeated visual surveys of sociable weavers to obtain presence-absence data of cape cobra and boomslang in sociable weaver colonies over an entire breeding season. I related the presence-absence data of the two snake species to spatially- and temporally-variable factors using principal component analyses (PCA) and multiple logistic regression analyses. The presence of snakes in sociable weaver colonies is primarily influenced by temporal factors, but spatial factors also play a role
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