Habitat-specific inter and intraspecific behavioral interactions among reef sharks

Area of Science:

• Marine biology
• Behavioral ecology
• Ecology

Background:

• Dominance interactions are key to animal social structures and species distribution.
• Interference competition can lead to habitat separation, but its role with weak agonistic interactions is less understood.
• Habitat variability can influence interference competition, impacting ecological models.

Purpose of the Study:

• To investigate the dominance hierarchy between blacktip reef sharks (Carcharhinus melanopterus) and gray reef sharks (Carcharhinus amblyrhyncos).
• To determine if habitat influences the strength of competitive interactions and spatial relationships between these two shark species.
• To assess the impact of intraspecific and interspecific competition on shark foraging behavior.

Main Methods:

• Utilized baited underwater cameras to observe behavioral interactions between sympatric reef sharks.
• Recorded relative abundance and dominance interactions in different reef habitats (forereef and backreef).
• Analyzed shark feeding behavior, specifically biting bait cages, in the presence of conspecifics and heterospecifics.

Main Results:

• A consistent dominance hierarchy was observed, with gray reef sharks being the dominant species.
• The inverse relationship between blacktip and gray reef shark abundance varied significantly by habitat.
• Shark abundance declined more sharply in forereef habitats compared to backreefs when heterospecifics were present.
• Gray reef sharks were more likely to access bait than blacktip sharks.
• Increased conspecific presence reduced individual shark willingness to forage.

Conclusions:

• Habitat-specific behavioral interactions, particularly dominance, may explain spatial separation between competing reef shark species.
• Gray reef sharks exert differential control over blacktip reef shark foraging success based on habitat.
• The findings highlight the importance of considering habitat context in understanding competitive dynamics in marine ecosystems.