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Male of common agama Agama agama basking in the sun. Limbe, Cameroon.

September 2019
Amphibia-Reptilia

Project: Risk-taking in wild living animals

Authors:

University of California, Los Angeles

Cover for Amphibia-Reptilia 2019, Vol. 40, No. 3. It is related to paper "Antipredator behaviour of old-world tropical lizard, common agama Agama agama, in an urban environment".

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Article

Antipredator behaviour of old-world tropical lizard, common agama Agama agama, in an urban environme...

August 2019 · Amphibia-Reptilia

Escape behaviour is a common antipredator strategy of lizards. Here, we studied the effect of several variables predicted to have a potential effect on escape behaviour of lizards. Specifically, we measured the effects of starting distance (SD), distance to cover, sex–age and the observer’s head orientation on flight initiation distance (FID) in the common agama Agama agama. Agamas were ... [Show full abstract] approached in urban localities in Limbe city, Cameroon, where they were habituated to the presence of humans. We found no association between FID and SD, but individuals closer to potential cover had shorter FID than individuals farther from a refuge. Juveniles escaped later than adults, but no significant differences were found in the FID between adult males and females. Head direction of the approaching observer had no effect on FID. This is, to the best of our knowledge, the first study investigating factors affecting FID in common agamas, extending our knowledge on risk-related behaviour in lizards of Old World tropics.

Pedestrian Density Influences Flight Distances of Urban Birds

July 2014 · Ardea -Wageningen-

Peter Mikula

Birds inhabiting urban areas have to cope with novel conditions. Unlike natural habitats, birds in urban environments are exposed to an increased human presence which often induces stress. Urban birds with reduced sensitivity to human disturbance can obtain benefits such as longer foraging time or decreased energy costs for escape. Here, I tested the hypothesis that the decrease in flight ... [Show full abstract] initiation distance (FID) to a potential predator (an approaching human) reflects adaptation to the level of disturbance expressed as pedestrian density. Moreover, I studied the influence of habitat type and species on observed FIDs. I analysed 2117 flight distances (20 species of European birds) located in ten localities in Prague. I found that species and pedestrian density play a more important role in determining FIDs than the type of habitat. Moreover, urban populations exposed to increased pedestrian density had consistently shorter flight distances. This study provides empirical documentation of changes in anti-predator behaviour, which strongly correlate with the pedestrian density gradient. It could support the idea that the establishment of FID can be highly plastic process depending on local conditions, as it is highly affected by a bird’s individuality and its ability to adapt to the local level of disturbance by learning.

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Morphological divergence, tail loss, and predation risk in urban lizards

December 2021 · Urban Ecosystems

Urbanisation changes the structure of natural habitats and alters trophic interactions, pressuring urban species to adjust and adapt. Unlike behavioural shifts that tend to be more flexible, morphological characteristics in vertebrates are less plastic and changes may come at a greater cost. We explored the hypothesis that morphological characteristics in a tropical agamid lizard Psammophilus ... [Show full abstract] dorsalis are not only selected to suit altered habitat conditions in urbanised areas but reflect predation risk in urban habitats. In addition, we explored differences in tail loss in both sexes from urban and rural habitats. First, we find that predation risk did not differ between urban and rural habitats, but differed between sexes. Conspicuous courtship-coloured male lizards were more likely to be attacked compared to cryptically-coloured female lizards. Next, we find that P. dorsalis differed in key morphological characteristics, with greater urban-rural differences in males than females. Urban lizards had shorter proximal limb elements, longer 4th digits and greater body mass than rural lizards; and among males, urban lizards had significantly larger head sizes and longer distal limb elements than rural lizards. Finally, we find that the rates of tail loss differed between habitats and sexes, with urban male lizards having greater rates of tail loss than rural males and all females. Inter-sexual difference in tail loss was consistent with the difference in predation risk between sexes, but tail loss differences between urban and rural habitats could not be explained by predation risk. In sum, we find that adaptations to novel urban environments are not exclusively driven by a single promoter (e.g. predation risk) but are influenced by multiple selection pressures with associated fitness costs, such as tail loss.

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