Meeting Abstract
The role of serotonin in driving social interactions, dominance hierarchies, aggression, and state of mind has been well-documented in a number of species, ranging from invertebrates to humans. The majority of previous work assaying serotonin to understand happiness or stress in animals has been limited to model organisms or smaller study species which can be kept and maintained under laboratory conditions. It is unsurprising, then, that we generally know much less about the role of serotonin in predator-prey interactions, particularly for large and mobile species which often experience a diversity of changing environments across their life history. We assayed plasma serotonin levels, a proxy for “happiness,” in two species of predatory sharks sampled in urban and rural environments in southern Florida. Bull sharks resident to the Bay of Miami had significantly higher plasma serotonin levels than bull sharks sampled in the Everglades National Park, where there is less human-impact. There were no significant differences in plasma serotonin between blacktip sharks sampled across urban and rural habitats, but their levels were significantly lower than bull sharks. Our results suggest that shark species which are hunted by larger species experience higher chronic stress and lower serotonin levels, whereas the benefits of urbanized living may be tracked neurologically and function to alter the ecological roles of sympatric top predators.
