Subject: Dolphin Aggression

Dagmar Fertl (
Mon, 04 Oct 1999 05:35:32 PDT

I, like so many others, love dolphins and would like to view
them as cute, loveable, harmless creatures.  However, I have
discovered some rather shocking information involving dolphin
attacks, both upon humans and porpoises.  I read a report written in
1995 saying that a male bottlenose dolphin (nicknamed Tiao), who
frequently visited a beach near Sao Paolo, Brazil, head-butted two
swimmers, hospitalizing one and killing the other.  There was reason
to believe that this attack was provoked by the swimmers.  Also,
people who participate in programs that allow them to swim with wild
dolphins (which I believe to be an incredibly stupid idea) have also
reported attacks including biting, head-butting, and other
aggressive acts.  I may understand the dolphins' reasons for
attacking these people because they are probably not accustomed to
the presence of humans in their territory.
However, the other cases concern me.  These have involved
dolphins beating and killing porpoises, the dolphins' cousins.  In
Moray Firth in Scotland, a total of 42 dead porpoises have been
found (between 1991 and 1993) washed ashore with "massive multiple
trauma." This is inflicted when they are rammed by dolphins. Several
theories for the dolphins' violent behavior have been made.  Some of
these include:  mistaken identity (the dolphins mistake the
porpoises for sharks), defending territory (the approximately 150
dolphins that live in the firth are joined every year by several
hundred porpoises passing through from the north Atlantic),
competition for food, establishment of some type of hierarchy, and
some sort of stress.  Increased boat traffic, pollution, and oil &
gas exploration have also been accused of disrupting the ecological
balance in the firth.

So my questions are:  Has any more information been discovered
concerning these aggressive attacks?  Have any new attacks been
reported in the last 3-4 years?  What are your thoughts on this

I was in a Dolphin Interaction Program about three months ago
at Sea World Cleveland in which I was allowed to actually get into
the water with captive dolphins and make physical contact with them.
I realize that there are often great differences between captive
dolphins and wild dolphins, but I still can't imagine such gentle,
loving creatures being involved in such violent acts.  I hope that
you can help me.  Thank you for your time:-)
Dolphins would really benefit from people not viewing them as god-like and 
angelic, but as wild, social animals, which they are.  Dolphins, like many 
other social mammals, use aggression in their social interactions with one 
another.  They do much hitting with their tails and beaks, as well as biting 
one another. For people to not anticipate that dolphins might do the same to 
them, is really not very enlightened. Whether in captive or wild situations, 
these are wild animals which can badly hurt people.  I tell people to 
compare dolphins to bears...would you try to feed or pet a wild bear? (I 
know that there are people who do so, and then are surprised when a bear 
attacks them).  I know that the 'permanent smile' they seem to have makes 
the dolphin look harmless, but the dolphin really isn't.   Also, as animals, 
people need to realize that dolphins and whales kill to eat. Whether it's a 
bottlenose dolphin killing a fish, or a killer whale killing a dolphin, 
fish, turtle, etc., it's still killing... quite simply.

As for the Moray Firth (north-east coast of Scotland) bottlenose dolphins 
still killing harbor porpoise - without my response being delayed by 
possibly a few weeks while I wait on a response from the researcher who 
observed all of this and wrote up his findings, I can't say whether more 
harbor porpoise attacked by bottlenose dolphins have been reported.  I can 
tell you that five out of eight young bottlenose dolphin calves found dead 
in Moray Firth a year or so ago were also killed by bottlenose dolphins 
(based on post-mortem exams). These data, together with direct observations 
of an aggressive interaction between an adult bottlenose dolphin and a dead 
bottlenose dolphin calf, provide strong evidence for infanticide in this 
population. The similarity in the size range of harbour porpoises and 
dolphin calves that showed signs of attack by bottlenose dolphins suggests 
that previously reported interspecific interactions could be related to this 
infanticidal behaviour.

I know that it seems horrifying to you, the thought of a bottlenose dolphin 
killing a 'relative', but it's something that some killer whales do all the 
time, and killer whales are just large dolphins...killing sperm whales, 
baleen whales, dolphins, porpoise, etc.  Also, infanticide occurs in other 
species of mammals, including lions.

Thanks for your very interesting question. It's very obvious you read a lot 
about dolphins. I hope this answers your question(s).


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