What now for aggressive bottlenose dolphins?

8th Oct 2014

The IWDG are aware of recent reports of single dolphins interacting aggressively with swimmers and bathers along the Irish coast.  We have not rushed to comment on individual reports due to the complexity of each incident, the limited information available and the practicality of any proposed solution.  We have instead, continued to urge the public not to enter the water or interact with any wild dolphin, including the solitary, sociable dolphins known as Dusty and Clet. 

However, the nature and severity of the most recent interaction, which resulted in the rescue of five swimmers off the coast of Galway, highlights a worrying progression in human-dolphin interactions in Irish waters.  Interactions are no longer confined to those initiated by humans seeking out contact with a dolphin, but now include unsolicited and unwelcome interactions with swimmers engaged in the responsible use of Irish waters.

"Clet" showing some old war wounds © Cormac CoyneThere have been many reports regarding these recent and traumatic events, however, there has been little in the way of informed comment.  This is due to the complex nature of these interactions and the difficulty in understanding the motives or drivers behind the dolphin’s behaviour.  There are a number of complex factors of significance in these events: 

·         The dolphin: while we can be reasonably confident that the species involved in all of these interactions is the bottlenose dolphin species, we cannot always be sure of the exact individual involved in specific incidents.  This has significance when attempting to attribute specific behaviours to specific dolphins.  If these types of interactions have developed to a stage where they require managing then it is imperative that we clarify which individuals are involved in which types of behaviours.

·         The Behaviour: our understanding of animal behaviour is still at a very early stage and we cannot be sure of the intended meaning behind many of the behaviours performed by cetaceans in Irish waters.  However, it is important that further information is gathered to investigate the nature of these interactions.  There are a number of behavioural possibilities.  The first is that these interactions may be intended by the dolphin in a playful manner, but due to the size and strength of this species of cetacean, may be perceived as aggressive by the swimmer.  The second is that this behaviour may start initially as play behaviour, but may evolve to aggressive behaviour following the reaction of the swimmer as perceived by the dolphin (i.e. this is not to blame the swimmer in any way for their reaction), or this behaviour may be intended by the dolphin as dominant, aggressive or sexual from the outset.  Identifying the nature of the behaviour, and its evolution during the interaction, may help to inform a management strategy.  Many authors have studied solitary dolphins and have documented significant changes in the behaviour of these animals over time.  Much of the evidence produced suggests that these changes in behaviour are learned and develop as a result of interactions with humans.  Wilke et al. (2005) identified four stages of evolution from a solitary, nonhuman-habituated dolphin to a highly interactive human-habituated, “solitary sociable” dolphin. Most of the solitary social dolphins are conditioned through these four stages to the presence and contact of humans.  Over time, the animal begins to seek out interactions, becomes increasingly forceful in these interactions and begins to exhibit behaviour hazardous to swimmers in the water.  Documented behaviours include preventing swimmers from leaving the water by repeatedly swimming in front of them to intercept their exit, increased activity levels and force of activity, tail slapping and breaching in close proximity or on top of swimmers, and biting or butting swimmers. 

Scene of the crime, Blackrock diving board, Galway


·         The solution: a contentious issue.  The question is, how do we un-habituate a wild dolphin to human presence and contact?  And if it is not possible, what are the consequences for both the human and the dolphin? 

It is not natural behaviour for a wild dolphin of any species to interact with humans in the wild.  Furthermore, it is not normal for a wild bottlenose dolphin to exist as a solitary animal without the presence and support of a family group.  And despite the protests of pro-dolphin swimmers, it is certainly not safe or responsible to enter the water, approach and attempt to interact in any way with a 4 metre, 200-300Kg wild apex predator.  In providing a solution to this problem we have a responsibility to consider the fact that we, as human beings, may have contributed to its development.  And we must recognise that this problem has consequences for the sociable dolphin as well as the safety of humans.  Habituation and attraction to humans and human activity are considered learned behaviour.  Two possible functions of habituation, desensitisation (decreasing responsiveness to a stimulus over time) and tolerance (tolerance manifests itself by the animal remaining near a stimulus regardless of its negative significance) have been shown to be harmful to the health and welfare of sociable dolphin as well as the safety of swimmers. 

Bottlenose dolphins interacting, Galway Bay Sept 2014

Can we make the dolphin wild again, or have we changed its nature forever?  And if we have changed its nature, has it been to its benefit?  Is it possible to control the behaviour of a wild dolphin?  If this dangerous behaviour cannot be controlled, then how do we prevent its occurrence?  These are extremely difficult questions to answer.  Particularly under the urgency of recent events.

The IWDG recognise the implications for the safety of swimmers in the presence of these dolphins and identify this as the most important issue.  However we also recognise that our experience and understanding of these events is extremely limited.  While we do not fully understand the motives behind these recent attacks, we must recognise the risks associated with such interactions.  The IWDG once again urges all members of the public not to attempt to interact with any wild dolphin.  This is the only way that the safety of the public can be guaranteed.

Paul Kiernan

IWDG Welfare Officer