With hurricanes Irma and Maria causing devastation to Caribbean islands and the US coasts, we’ve been very concerned for dolphins and orcas held captive in marine parks in these regions. But how do wild dolphin populations cope with such ‘monster storms?’ What is the impact on their communities?
This is a pertinent question, given global warming and the possibility of more and larger hurricanes in coming years.
Of course, no one studies dolphins during a hurricane – that would be too dangerous. But researchers have looked at the consequences for dolphin communities, and these investigations clearly show that dolphins can suffer heavily in large storms.
Hurricane Katrina had a devastating impact on captive dolphins and wiped out about a third of one local wild bottlenose dolphin population in the Gulf of Mexico in 2005. In the early 2000s, the bottlenose and Atlantic spotted dolphins in the Bahamas lost many members of their communities in a hurricane.
Dolphins, like people, can have their lives and communities ripped apart. But, although we have no idea of the long-term emotional impact on individuals, dolphins are responsive and intelligent and, as a community, they adapt.
In one study, researchers found how dolphins restructured their social life significantly after a hurricane. Lost members were ‘replaced’ by dolphins entering the community from outside; evidence of the complex and at the same time flexible nature of dolphin societies. One year later researchers observed a baby boom. Many mothers had lost their young but the community appeared to adjust with a sudden increased reproduction rate.
Even more intriguing was the study that found levels of aggressive behaviour between bottlenose and Atlantic spotted dolphins had decreased in the aftermath of a hurricane. The males of these two species were known to fight on a regular basis, but this behaviour reduced after the two communities both lost members.
We’re in the early days of research into the impact of hurricanes on whales and dolphins and we’ve much to learn. We know there can be a devastating impact on populations, followed by changes in behaviours to adjust. And in the period after a heavy storm there may even be small ‘silver linings,’ for example a smaller number of fishing boats in the area in the months and years post hurricane leaving more food for the dolphins.
But we don’t yet know what happens in the longer term. A wild population might adjust to the impact of one major storm, but what if climate change means that such events become more frequent? If there is an increase in intensity and frequency, it will mean more dolphins dying.
WDC is concerned not just with our impact on the conservation of populations and species, but also on the welfare of individuals. We represent dolphins and whales at the highest diplomatic level at international conventions where decisions are made that will affect their future. We provide governments and other decision-makers with the scientific information that they need to make informed choices.
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Changes in interspecies association patterns of Atlantic bottlenose dolphins, Tursiops truncatus, and Atlantic spotted dolphins, Stenella frontalis, after demographic changes related to environmental disturbance (Cindy R. Elliser, Denise L. Herzing) Marine Mammal Science 2016
Potential effects of a major hurricane on Atlantic bottlenose dolphin (Tursiops truncatus) reproduction in the Mississippi (Lance. J. Miller, Angela D. Mackey, Tim Hoffland, Stan A. Kuczak II) Marine Mammal Science 2010
Replacement dolphins? Social restructuring of a resident pod of Atlantic bottlenose dolphins, Tursiops truncatus, after two major hurricanes (Cindy R. Elliser, Denise L. Herzing). Marine Mammal Science 2010
Community structure and cluster definition of Atlantic spotted dolphins, Stenella frontalis, in the Bahamas (Cindy R. Elliser, Denise L. Herzing). Marine Mammal Science 2012