1,720,992 research outputs found
Context-dependent behavioural lateralization in the european pond turtle, emys orbicularis (Testudines, Emydidae)
No full textLateralization presents clear advantages in ecological contexts as the dominance of one brain side prevents the simultaneous activation of contrasting responses in organisms with laterally located eyes. This is crucial in selecting a safe refuge during a predatory attack and may strongly affect predator-prey interactions. We explored the possible presence of lateralization in the anti-predatory behaviour of European pond turtles, considering their escape facing a possible predatory attack. Thirty individuals (17 males, 13 females) were exposed to three different environmental situations of gradually increasing predatory threat: escape underwater from an unsafe shelter, diving into the water from a basking site and righting after being overturned. All turtles were tested 20 times for each of the three experiments (60 trials per individual; 1800 overall trials). We recorded multiple behavioural responses in the general context of predation risk. This was done in order to assess both the existence of lateralization and possible correlations among different behaviours as function of lateralization. The number of significant responses to the left sidewas always prevalent in each of the three simulated anti-predatory situations, suggesting the existence of a lateralized behaviour in this species. At the individual level, the differences we found in the three experiments could be related to different ecological contexts and consequent risk of predation. Our findings, among the few on chelonians, support the possible involvement of right hemisphere activity and, most importantly, reveal how the complexity of a general predatory context can affect the laterality of escape behaviour
Long-term Changes in food intake by Grey herons (Ardea cinerea), Black-crowned night herons (Nycticorax nycticorax) and Little egrets (Egretta garzetta) foraging in rice fields in Italy.
No full textIn northwestern Italy, traditional rice cultivation using permanent flooding has been replaced by cultivation that uses a reduced water depth and a shortened submersion period. Prey availability for the numerous herons and egrets using this intensive rice cultivation region changed as well, with a diminution of amphibians and an increase of crayfish (Procambarus clarkii) and oriental weatherfish (Misgurnus anguillicaudatus). The prey intake in 2014 was compared with data available for 1987 for the three most common species of waterbirds that forage in the paddies. Total biomass intake by Grey Herons (Ardea cinerea) feeding in the paddies decreased from 28 g dry mass/min in 1987 to 7 g in 2014, and by Black-crowned Night-Herons (Nycticorax nycticorax) from 8 g to 5 g, while the intake by Little Egrets (Egretta garzetta) remained similar (12 and 13 g in 1987 and 2014, respectively). The observed levels of prey intake allowed breeding Grey Herons to meet their energy needs by feeding exclusively in the rice paddies in 1987, but not in 2014. The other two study species could not meet their daily requirements for successful breeding by feeding in the paddies only, either in 1987 or 2014. Yet the three species bred successfully in the study area, and their reproductive output remained stable both in 1987 and 2014. Successful breeding was probable by the three species foraging in other habitats, such as rivers, small natural wetlands and irrigation canals, in the region
Indicators of biodiversity in an intensively cultivated and heavily human modified landscape
Full text linkNowadays, the loss of biodiversity in agroecosystems due to the intensification of farming practices is happening very fast, and therefore, stopping or slowing it down should be a priority for conservation. To detect changes in these environmental contexts, one approach contemplates focusing on a limited set of indicator species that can alert us to ongoing changes in progress. In this research, we aimed to measure the biodiversity of vertebrates using a multi-taxa approach in an intensively cultivated and highly inhabited area located in northern Italy. We investigated the relationships between biodiversity and environmental characteristics and we identified the taxonomic groups that can be used as indicators of biodiversity. Data collection was carried out in 2016 with different methods depending on the taxonomic group, in 131 sampling units chosen using a Tessellation Stratified Sampling. Then we calculated for each sampling unit a standardized Biodiversity Index, which was related to environmental variables concerning the land use and the landscape configuration using Multiple Linear Regression Analysis and Information-Theoretic approach. We used correlation analyses and the Indicator Species Analysis (IndVal) to identify the taxonomic groups and species that can be used as indicators of biodiversity. Biodiversity was positively related to the number of patches of natural vegetation, whereas it was negatively affected by the number of patches of artificial surfaces and by habitat diversity. Our findings agree with those obtained by many other researchers, which pointed out that agroecosystems provide adequate shelters, suitable foraging habitats and nesting sites. The negative effect of habitat diversity was explained by the area-heterogeneity trade-off. Therefore, sites with high heterogeneity will not contain enough cover of residual natural vegetation, essential to maintain high biodiversity, because increasing compositional heterogeneity within a fixed area simultaneously reduces the surface of each cover type. The analyses showed that birds and reptiles might be used as biodiversity indicators of vertebrates. Eurasian Magpie and Green Whip Snake, both generalist species, were associated with sites of low biodiversity, whereas seven birds, both generalists and farmland specialists, were associated with sites of medium biodiversity. In high biodiversity sites there were not indicator species. To conclude, in less natural environments, such as urban and agricultural landscapes, a combination of specialist and generalist indicator species seems adequate to monitor biodiversity changes. Our findings increase the knowledge of these very dynamic ecosystems, being important both to plan strategies for biodiversity conservation and to guarantee ecosystems services useful for humans
First report of adult Podarcis siculus (RAFINESQUE-SCHMALTZ, 1810) predation by Tarentola mauritanica (LINNAEUS, 1758)
No full textCross-specificmortality and differential occurrence of aberrant phenotypes in tadpolesaccording to P. kl. esculentus hemiclones’ assortment
No full textContinuous and discrete quantity discrimination in tortoises
No full textThe ability to estimate quantity, which is crucially important in several aspects of animal behaviour (e.g. foraging), has been extensively investigated in most taxa, with the exception of reptiles. The few studies available, in lizards, report lack of spontaneous discrimination of quantity, which may suggest that reptiles could represent an exception in numerical abilities among vertebrates. We investigated the spontaneous ability of Hermann's tortoises (Testudo hermanni) to select the larger quantity of food items. Tortoises were able to choose the larger food item when exposed to two options differing in size, but equal in numerousness (0.25, 0.50, 0.67 and 0.75 ratio) and when presented with two groups differing in numerousness, but equal in size (1 versus 4, 2 versus 4, 2 versus 3 and 3 versus 4 items). The tortoises succeeded in both size and numerousness discrimination, and their performance appeared to depend on the ratio of items to be discriminated (thus following Weber's Law). These findings in chelonians provide evidence of an ancient system for the extrapolation of numerical magnitudes from given sets of elements, shared among vertebrates
Is It Worth the Risk? Food Deprivation Effects on Tadpole Anti-Predatory Responses
No full textPredation risk affects foraging behavior and, particularly, the amount of time devoted to the search for food. When exposed to predation risk, food deprived animals should be risk prone and relax behavioral defenses to a wider extent than well fed individuals. To test for this prediction, we used a 2 × 2 factorial design experiment, manipulating both the energetic state (fed vs. fasted) and exposure to an attack-released cue (injured vs. uninjured conspecifics) of common water frog tadpoles (Pelophylax kl. esculentus). Contrary to expectations, food deprivation significantly lowered the activity level of predator-exposed tadpoles. As in this experiment no food resource was added to test containers, energy conserving behavior might have both delayed starvation and lowered the probability of encountering the potential predator. To test for the effect of food availability on behavioral responses, we performed a second experiment, using the same protocol and procedures, except for adding food to all test containers. All tadpoles showed similar levels of activity, while fed tadpoles exposed to alarm cues tended to swim farther from the cage containing the stimulus than in the first experiment. As many anuran larvae can feed on dead conspecifics, prey-borne cues may have been interpreted as the potential presence of both a food source and a predator, fed tadpoles possibly being more confident than fasted tadpoles in their ability to escape predation in case an actual attack occurs
Discrimination of group numerousness under predation risk in anuran tadpoles
No full textFor social animals, group size discrimination may play a major role in setting the trade-off between the costs and benefits of membership. Several anuran tadpoles show different degrees of social aggregation when exposed to the risk of predation. Despite the importance of aggregative behaviour as an anti-predatory response, the mechanism underlying tadpole choice of the group to join to has not been sufficiently investigated. To establish whether visual cues provide sufficient information to enable tadpoles to choose between aggregations differing in size, we explored the abilities of the larvae of two anuran species (green toad Bufotes balearicus and edible frog Pelophylax esculentus) to discriminate among four numerical combinations of conspecific tadpoles (1 vs. 4, 3 vs. 4, 4 vs. 6 and 4 vs. 8), either in the presence or absence of predatory cues. Our results suggest that in anuran larvae the capacity to discriminate between quantities is limited to small numbers (1 vs. 4 for B. balearicus and both 1 vs. 4 and 3 vs. 4 for P. esculentus). Predator-exposed toad tadpoles stayed longer close to the larger group, supporting aggregation as a major anti-predator behaviour in bufonids, while frog tadpoles showed a preference for the smaller groups, though in predator-free trials only, probably associated with lower intra-specific competition
Righting behaviour in the European pond turtle (Emys orbicularis): relations between behavioural and morphological lateralization
No full textLateralization represents a key property of many behavioural traits, with the right and left sides of the brain providing different and integrative functions. Common ecological contexts where lateralization can be observed are foraging and predatory ones, where both visual and auditory lateralization may provide advantages such as faster response and increasing neural processing capacity. This is crucial in selecting a safe refuge during a predatory attack and may strongly affect the outcome of predator–prey interactions. For animals like turtles, a critical condition may occur when they are overturned on their own shell, which causes difficulties in breathing and thermoregulation, making them more vulnerable to predators. Therefore, the ability to right is a critical adaptive component related to survival in aquatic turtles, which has been observed to be lateralized. However, an overlooked feature of behavioural lateralization is its possible relationship with asymmetry in external morphology. Here we investigated this topic in freshwater European pond turtles Emys orbicularis, looking at a possible relation between lateralization in righting behaviour response and asymmetry in the shape of turtles’ plastron and carapace. Righting performance (total time needed to completely turn) appeared to depend on shell shape. We found that none of the morphometric variables was related to a lateralization index calculated as the first side from which turtles tried to right. However, a strong negative correlation between the asymmetry index of plastron and the turning direction emerged, with more symmetric animals tending to turn to the right side
Freshwater turtles reveal personality traits in their antipredatory behaviour
No full textAnimals respond to predation risk with antipredatory behaviours that may disclose the presence of different personality traits among individuals in a population, and how populations may differ for the expression of those traits. Variation among individuals is a necessary condition for the evolution through natural selection and inter-individual behavioural differences may be selected in different environmental situations. We tested whether individuals of two freshwater turtle species, Emys orbicularis and Mauremys leprosa, show consistent risk-taking behaviour when exposed to the presence of a potential predator. In an outdoor experimental setting, we simulated a predatory attack by overturning a turtle onto its carapace and recording three different behavioural response variables. Our results showed clear differences between species. The appearance time was highly consistent over the trials for both species, but was shorter for E. orbicularis and very long for M. leprosa. Waiting time was consistent only for females of E. orbicularis while M. leprosa did not show repeatability and had significantly longer waiting times. The number of failed righting attempts, likely being partially dependent on turtle individual performance, was highly consistent during the experiment for both species. The hiding behaviour in both species of freshwater turtles was consistent over time and, therefore, could be regarded as a personality trait. However, the differences in waiting times consistency suggested possible differences in defensive strategies between sexes and species
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