Dolphins: A Newfound Antagonism Towards Manatee Calves

Study Highlights

Recent observations have unveiled a disturbing trend of aggressive behavior by bottlenose dolphins (Tursiops truncatus) towards Antillean manatee calves (Trichechus manatus manatus). A study published in PLOS One documented 10 instances of such aggression, shedding light on a previously overlooked aspect of dolphin behavior with potential implications for manatee populations.

Aggressive Interactions

The study’s findings paint a troubling picture of dolphins harassing, ramming, and biting manatee calves, often resulting in injury or even death. These aggressive interactions were observed in various locations, involving both orphaned and mother-accompanied calves. Notably, the majority of attacks occurred between 2015 and 2020, suggesting a recent escalation in hostility.

Intentional Attacks

Researchers believe that the attacks were deliberate and intended to inflict harm or even death on the calves. Evidence supporting this conclusion includes observations of dolphins actively attempting to separate calves from their mothers and the presence of tooth rake marks on orphaned calves. This behavior is particularly alarming, as it indicates a level of aggression beyond mere play or territorial defense.

Dolphin Behavior Patterns

While aggressive behavior towards their own young and calves from other species is not entirely new among dolphins, the frequency and severity of attacks on manatee calves raise concerns. Previous records indicate that dolphins have attacked and killed harbor porpoises (Phocoena phocoena), and worldwide instances of bottlenose dolphins engaging in violent behavior towards other species have been reported.

Potential Causes and Implications

The underlying causes of this newfound antagonism towards manatee calves remain unclear, but several factors may contribute to the observed behavior.

Competition and Habitat Overlap

One potential explanation lies in competition for resources. Dolphins and manatees share similar habitats and diets, which may lead to perceived competition for food, space, or mates. Climate change and human activities that degrade ecosystems could further exacerbate this competition by causing habitats to overlap more significantly.

Dolphins’ Sophisticated Behavior

Bottlenose dolphins are known for their large brains, complex emotions, and distinct cultural traits. The aggressive interactions between manatees and dolphins over an extended period suggest a learned or ingrained behavior. Researchers speculate that dolphins may view manatee calves as easy prey or see them as a threat to their young.

Conservation Concerns

The aggressive behavior of dolphins poses a significant threat to the survival of Antillean manatees, a threatened subspecies of the West Indian manatee. With a population estimated at around 1,700 individuals, any additional mortality factors could have a devastating impact. Additionally, vessel collisions pose an additional threat to the relatively healthy manatee population in Belize.

Conclusion

The study’s findings highlight a previously overlooked aspect of dolphin behavior and its potential consequences for manatee populations. Further research is needed to delve deeper into the motivations behind these attacks and to develop strategies to protect calves and the wider manatee population. Understanding the underlying causes of the aggression is crucial for developing effective conservation strategies that safeguard both dolphins and manatees.