UIE-E - Artigos em revistas nacionais
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Browsing UIE-E - Artigos em revistas nacionais by Author "Burford, Fiona R. L."
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- Chorusing by male european fiddler crabs, Uca tangeri: A study of visual communication netwoksPublication . Burford, Fiona R. L.; McGregor, Peter K.; Oliveira, Rui FilipeChorusing behaviour, in which males aggregate and advertise to attract females, has been extensively studied in acoustically signalling orthopterans and anurans. Species which agregate and signal visually have comparanble behaviour but chorusing aspects has been studied infrequently. Male fiddler crabs (genus Uca) signal by waving and enlarged claw and form signalling aggregations, therefore, they have a potential to form a visual chorus. This study investigated the chorusing behaviour of male eurpoean fiddler crabs, Uca tangeri. The timing of waving by groups of three males (trios) was studied when each male was alone and when all three males were present. When waving in a trio, the male with the largest claw significantly increased the lenght of its interwave interval and some such males tend to wave soon after the other males. This pattern of waving may enhance the effectiveness of the large-claw males signal by avoiding visual object grouping and by allowing females to assess relative claw size more readily.
- Considerations on the use of video playbacks as visual stimuli: The Lisbon workshop consensusPublication . Oliveira, Rui Filipe; Rosenthal, Gil G.; Schlupp, Ingo; McGregor, Peter K.; Cuthill, Innes C.; Endler, John A.; Fleishman, Leo J.; Zeil, Jochen; Barata, Eduardo Nuno; Burford, Fiona R. L.; Gonçalves, David; Haley, Michael; Jakobsson, Sven; Jennions, Michael D.; Körner, Kay; Lindström, Leena; Peake, Thomas; Pilastro, Andrea; Pope, Denise S.; Roberts, Sam G. B.; Rowe, Candy; Smith, Jerome; Waas, Joseph R.This paper is the consensus of a workshop that critically evaluated the utility and problems of video playbacks as stimuli in studies of visual behavior. We suggest that video playback is probably suitable for studying motion, shape, texture, size, and brightness. Studying color is problematic because video systems are specifically designed for humans. Any difference in color perception must lead to a different color sensation in most animals. Another potentially problematic limitation of video images is that they lack depth cues derived from stereopsis, accommodation, and motion parallax. Nonetheless, when used appropriately, video playback allows an unprecedented range of questions in visual communication to be addressed. It is important to note that most of the potential limitations of video playback are not unique to this technique but are relevant to all studies of visual signaling in animals.
- Human exploitation of male fiddler crab claws: Behavioural consequences and implications for conservationPublication . Oliveira, Rui Filipe; Machado, José Luis Gorjão H. C.; Jordão, Joana; Burford, Fiona R. L.; Latruffe, Claire; McGregor, Peter K.Male fiddler crabs have one of their feeding claws greatly enlarged, which may comprise up to 40% of their weight. In southern Portugal (Ria Formosa) the major claw of the fiddler crab Uca tangeri is a local delicacy. Fishermen break off the male major claw and throw the crab back into the mudflat to regenerate a new one. Approximately 38 % of the males sampled had a missing or a regenerating claw. Although individuals are not removed from the population the operational sex ratio is biased towards females since other males and females behave towards clawless males as if they were females. Moreover, removing the major claw from males prevents them from signalling (waving display) to females to attract them to their breeding burrows and it also places them at a disadvantage if they have to defend their burrows from males with intact claws. Thus, the harvesting of male fiddler crab claws has potential consequences at the population level. In this paper we investigated these potential consequences by comparing an exploited population of fiddler crabs at Ria Formosa with a remote population at the Mira estuary that is not under human exploitation. The unexploited population has significantly larger males and a significantly higher density of burrows. The operational sex ratio is also significantly different between the two populations with a female-biased sex ratio in the exploited population. These preliminary results suggest that claw harvesting in fiddler crabs has a measurable effect at the population level. The consequences of this type of fishery in which the individuals are not removed from the population but the population structure is potentially affected need further investigation.