1,721,035 research outputs found
The need for adequate statistical analyses to estimate gender imbalance: A comment on Teixeira da Silva and Dobránszki (2019)
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Individual trophic specialisation in the Alpine newt increases with increasing resource diversity
No full textDietary studies suggest that amphibians are opportunistic predators. However, there is little information on the ability of individuals to change their feeding strategy in time because most studies do not evaluate prey availability and its effect on individual behaviour. To better understand how variation in prey availability may affect the feeding strategy of newts, we studied the Alpine newt, Ichthyosaura alpestris, during April and June in 2015, when we monitored prey availability and the species dietary habits. In April at low prey diversity, the newts were generalists, i.e., their diet overlapped almost completely with prey availability. In June when prey diversity was high, the newts became specialists. At the individual level, 9 out of 15 recaptured newts shifted from a generalist to a specialist feeding strategy from April to June, suggesting a rapid behavioural change in response to increasing prey diversity, in accordance with optimal foraging theory. These results stress the importance of sampling the same individuals several times during an extended period of time to better understand the patterns of diet variation in amphibians
Reliability of multinomial N-mixture models for estimating abundance of small terrestrial vertebrates
No full textInformation on population abundance is important to correctly plan conservation and management of animal populations. In general, capture-mark-recapture (CMR) is considered the most robust technique to estimate population abundance, but it is costly in terms of time and effort. Recently, binomial N-mixture models, based on counts of unmarked individuals, have been widely employed to estimate abundance. These models have limits and their reliability has been criticized. In the majority of cases, multinomial N-mixture models based on multiple observer protocols, that are hierarchical extensions of simple CMR, are applied in estimating abundance of animals with large body size, conspicuous behavior or high detection probabilities. We applied and evaluated the reliability of a multinomial N-mixture modelling approach with multiple observer data to a small and cryptic terrestrial salamander, found in different habitats where populations possess different level of detectability. Estimates obtained with multinomial N-mixture models were compared to estimates obtained with classical methods, such as removal sampling, and their reliability has also been evaluated by simulations scenarios. Our results show that multinomial N-mixture models, applied within a multiple observer framework, give reliable and robust estimates of population abundance even when detection and density are relatively low. Therefore, multinomial N-mixture models appear efficient and cost-effective when planning and identifying management actions and conservation programs of small terrestrial animals such as amphibians and reptiles. © 2020, Springer Nature B.
Trophic strategies of two newt populations living in contrasting habitats on a Mediterranean island
No full textIn amphibians, the study of trophic niche is important to better understand the species ecological adaptation, in particular along gradients or in heterogeneous habitats. In this framework, we analysed the trophic strategies of two populations of the endemic Corsican brook newt Euproctus montanus, one living in a Mediterranean lowland and the other in a mountain stream. In both sites, we performed dietary analysis using stomach flushing and assessed the available invertebrate prey community. Further, we estimated newt density using removal sampling. Streams were similar in invertebrate prey abundance (P = 0.15), but differed in prey diversity (P < 0.001), the Mediterranean lowland site possessing a higher diversity of invertebrate prey. The newts’ trophic strategies were analysed at the population level and also at the individual one to assess in detail the trophic specialization. In both sites newt density was similar and the population realized trophic niche displayed a large overlap with the available prey community. Therefore, both populations behaved as broad trophic generalists. However, in the Mediterranean lowland stream, where available resources were more diverse, there was evidence of a significant degree of individual trophic specialization. This finding is consistent with the classic niche variation hypothesis, that predicts a higher individual differentiation in presence of high resource diversity
European Plethodontid Salamanders on the Forest Floor: Testing for Age-Class Segregation and Habitat Selection
No full textIs the Northern Spectacled Salamander Salamandrina perspicillata aposematic? A preliminary test with clay models
No full textThe role of familiarity in shelter site fidelity: insights from a mesocosm experiment with a plethodontid salamander
No full textBehavioral adaptation is one of the first responses put in play by individuals to buffer environmental variations and to maintain homeostatic equilibrium with their environment. Microhabitat selection is pivotal for maximizing fitness, survival and reproduction, but how individuals process and exploit information acquired from the environment to make future microhabitat choice is yet understudied. In this study, we used outdoor mesocosms in which we introduced Strinati’s cave salamanders (Speleomantes strinatii), to assess their behavioral patterns of shelter site fidelity. In each mesocosm three microhabitats were available to the salamanders: the leaf litter, a log and a rock. A total of 22 salamanders were tested over an 8-day period, 11 in autumn and 11 in spring. Salamanders shelter site fidelity was driven by both microhabitat humidity and previous experience obtained in the mesocosm. In our experiment, the time spent in the mesocosm was the main factor influencing shelter site fidelity, suggesting that previous experience and familiarity are important in salamanders’ behavioral adaptation. Therefore, cave salamanders are capable of learning from experience when selecting their shelters, a behavior that could also be relevant during migration, colonization of new environments and adaptation to climate change
Estimating abundance of the Stripeless tree-frog Hyla meridionalis by means of replicated call counts.
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