Ecological Patterns and Processes in Mangrove Ecosystems Ii Problem Set
PRACTICAL 3 ECOLOGICAL PATTERNS AND PROCESSES IN MANGROVE ECOSYSTEMS II
PROBLEM SET
1. BIOLOGICAL INTERACTION
During our Field Trip to the Cairns Airport Mangrove Boardwalk on 7th August, 2013, I observed a distinct distribution pattern in the locations of the Orange-Clawed Fiddler Crabs (Uca coarctata). Upon further investigation, I noticed that the larger males of the species (easily identifiable as those with one large claw) colonised the open areas located beside the Middle Creek viewing platforms, that were in full sun for a larger part of the day, and offered no protection from predators. Conversely, the smaller females colonised the shadier and more forested area on the banks of the small stream, located between the two platforms, approximately 50 and 90 paces either side respectively, along the boardwalk. I was intrigued as to why this would be so.
2. FUNCTIONAL HYPOTHESIS
The male Orange-Clawed Fiddler Crab (Uca coarctata) avoids shaded and vegetated habitats that hinder visibility. Inhabiting open and less structured mud-flat areas enable the male Fiddler Crab better visibility for predator detection, and improved scope for the use of courtship signals.
Male Fiddler Crabs rely upon their large claws for the provision of visual aids in many aspects of their day to day existence. They use their claws in territorial defence in order to ward off antagonistic males. Their complex signals also aid females in detection of, and their approach to, males of the same species. Wandering burrow-mating females may visit up to 100 males before making a choice of mate. Interestingly, those males who lose their claws, will regenerate another claw that requires less energy to function, thus making it more effective at signalling, and possibly leading to more successful meetings with females. As the male Fiddler Crab is quite dependent upon visual cues, it needs to create its home in an open, flat environment with few structures able to obstruct
PROBLEM SET
1. BIOLOGICAL INTERACTION
During our Field Trip to the Cairns Airport Mangrove Boardwalk on 7th August, 2013, I observed a distinct distribution pattern in the locations of the Orange-Clawed Fiddler Crabs (Uca coarctata). Upon further investigation, I noticed that the larger males of the species (easily identifiable as those with one large claw) colonised the open areas located beside the Middle Creek viewing platforms, that were in full sun for a larger part of the day, and offered no protection from predators. Conversely, the smaller females colonised the shadier and more forested area on the banks of the small stream, located between the two platforms, approximately 50 and 90 paces either side respectively, along the boardwalk. I was intrigued as to why this would be so.
2. FUNCTIONAL HYPOTHESIS
The male Orange-Clawed Fiddler Crab (Uca coarctata) avoids shaded and vegetated habitats that hinder visibility. Inhabiting open and less structured mud-flat areas enable the male Fiddler Crab better visibility for predator detection, and improved scope for the use of courtship signals.
Male Fiddler Crabs rely upon their large claws for the provision of visual aids in many aspects of their day to day existence. They use their claws in territorial defence in order to ward off antagonistic males. Their complex signals also aid females in detection of, and their approach to, males of the same species. Wandering burrow-mating females may visit up to 100 males before making a choice of mate. Interestingly, those males who lose their claws, will regenerate another claw that requires less energy to function, thus making it more effective at signalling, and possibly leading to more successful meetings with females. As the male Fiddler Crab is quite dependent upon visual cues, it needs to create its home in an open, flat environment with few structures able to obstruct