Community | September 03, 2008 | 35 comments

Bottlenose dolphins may be attacking other species over food shortages

source: http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/09/03/eadolphin103.xml

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goldenways
Bottlenose dolphins suffering from food shortages may be killing their sibling species to take out the competition, scientists have warned.

A series of dead porpoises and young bottlenose dolphins washed up the country's coastline have borne the animal's teeth marks.


But the appearance of the body of a rare baby Risso's dolphin on a beach in the Scilly Isles has raised fears that bottlenose dolphins may be becoming more aggressive in its desperate search for food.

The latest victim, which washed up in St Agnes, was young enough to still be dependent on its mother for nourishment and researchers believe it was killed by an adult predator.

Risso's dolphins have tall dorsal fins, extensively-scarred, almost stripy black bodies and blunt heads. They are often seen around Cornwall although not as frequently as bottlenose and common dolphins. It is the first time one has been linked with a fatal attack by bottlenoses.

The baby dolphin has been brought back to the mainland where it will undergo a post-mortem examination.

Jan Loveridge, volunteer co-ordinator for Cornwall Wildlife Trust's Marine Strandings Network, said: "Despite their friendly image bottlenose dolphins can be aggressive towards one another and on the rare occasion that we see a dead bottlenose wash ashore it often has rake or tooth marks inflicted by its own species.

"But we have recently begun to see an increase in the numbers of young and female harbour porpoise that have clearly been attacked by bottlenose dolphins and results from the post mortems carried out on these animals confirm this.

"The discovery of yet another species that has suffered from these attacks is of particular interest especially as it was so young.

"The motives for such attacks are unclear, although scientists have considered that competition for declining food stocks may trigger the behaviour."

Dr Peter Evans, director of Sea Watch Foundation, said the Risso's dolphin may simply have been mistaken for a porpoise.

"Risso's dolphins feed on things like squid and cuttlefish and octopus, which are rarely eaten by bottlenose dolphin, which feed predominantly on fish," he said.

"It was quite possible that it was quite vulnerable because of its size and was mistaken for a porpoise. Young Risso's look a bit like porpoises."
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35 comments // Bottlenose dolphins may be attacking other species over food shortages

  • MissAmanda
  • arcticspirit
  • arcticspirit
  • arcticspirit
    • 0
      arcticspirit  

    • Do these revelations mean that dolphins may be closely related to man on an intelligence level? We can definitely say that dolphins have complex social structures. Also, a lot of the dolphin social behavior and structure is similar to primates, which again suggests that dolphins are close to the human intelligence level.
      In human society one of the many things that these alliances do is approach members of the opposite sex. The same is true in dolphin society except that dolphins often approach the females aggressively, while the same behavior in humans(gang rape) is much less common. In dolphins, this is common, and alliances that go after females are likely to be related, in humans this is less common.

      Finally, the last issue I will address is the idea of sex for fun.
      In my opinion, an animal that has sex for purposes other than reproduction is probably more likely to be related to humans intellectually.
      Earlier I stated that alliances are more likely to herd non-pregnant female it has been proven that dolphins do enjoy sex.
      Dolphins have been recorded having homosexual sex and there is no chance for reproduction there. So perhaps the dolphins in the alliances are also having sex for fun but since they don't have the worries of fatherly duties they may as well have sex with non-pregnant females.
      (more)

      Comment by arcticspirit:
      Freaking Mammals.

    • 3 years ago
  • arcticspirit
    • 0
      arcticspirit  
    • Image

    • I can't believe I am putting dolphin porn on the internet, Here are studies of homosexual dolphin sex for fun, Gang rape of females... and more. But discovery channel put it on tv first. I freaked when I realized they were showing multiple dolphin penises in one clip and only one female. One dolphin penis is visible in this pict (eww yeah).. but this female is about to be penetrated by the whole gang.

      Last year on Discovery they showed a female dolphin being freaking gang raped and held hostage by males. Surprise anyone?

      Alliance Strategies in Bottlenose Dolphins
      Emma Berdan

      Dolphins have long been considered some of the smartest animals next to humans. They exhibit complex behaviors such as: social hierarchy, formation of alliances, what appears to be suicide(1) and cooperative behavior.

      Researchers have been studying the bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia for quite a long time because they are tame. They have observed male-male alliances that seem very stable. Male alliances are usually groups of two or three males that can last many years.

      So why do males form these alliances? The answer seems to greatly reflect human behavior: to get women. Male alliances typically "herd" females. These herding events are not usually enjoyed by the females. Herding is often forcible with escape events and violence involved.(3) In a herding event males will surround the female or chase her. Aggression toward the female is common, Of course the ultimate goal of a herding event is sex and the males in the alliance will take turns to make sure everyone has an equal share.
      What has just been described is a primary alliance. However, bottlenose dolphins also form secondary alliances. Once again these are between males.

      I will briefly touch on the third type of alliance, the super alliance.Labile alliances are ones in which males change partners frequently. The observed super-alliance consists of 14 males. Each male of the alliance has 5 to 11 alliance partners from within the super alliance. The super alliance is another example of the social complexity found in these dolphins.

      We know the dolphins form these alliances to get women but are they looking for sex or to reproduce? Alliances are likely to herd non-pregnant females that are likely to be in estrus.
      So we can assume that although fun may be had, the overall goal is reproduction. Since there is equal sharing of the female, according to the theory of fitness we would expect males in an alliance to be related. However, males in a super alliance are not usually related at all.(5) Why then would a male choose to be in the super alliance? One answer could be that since the super alliance is so big they can basically take on all of the primary and secondary alliances and steal many females.
      Therefore the males in the super alliance would have more access to females. Perhaps that would make up for what fitness is lost by not allying with related dolphins.

      (continued below)

    • 3 years ago
  • regularrf
  • willyb
    • 0
      willyb  

    • Sounds like we need to leave the oceans alone. I was at a seafood restaurant this weekend on the coast. The menu said "all our food is non-farm, pure ocean goodness". I commented to my wife that I would feel better knowing that the fish were farm raised. They would probably be healthier and I'd know we aren't weakening the oceans.

    • 3 years ago
  • ghostbar
    • 0
      ghostbar  

    • This is a totally natural reaction. In fact, remember that this dolphins are very intelligent and does have a hierarchy like us the humans but they weren't all around bothering about who created the world and what laws he gave us so they don't use that part that most of us have called morality.

      This is normal and when it comes to they what cares is the maintenance of the race/specie.

    • 3 years ago
  • Mr_Black_PennState
  • purplefox
    • 0
      purplefox  

    • I knew there was something sinister about their cute dolphiny smiles - just look at those sharp teeth. Seriously though, that's pretty sophisticated behaviour, killing off your rivals. Humans would easily do the same if any other species threatened them with such competition...

    • 3 years ago
  • Smothmoth
  • ximalim
  • SDLN
    • 0
      SDLN  
    • ximalim:

      You might already know this; but if not, here are some instructions for posting youtube vids in the comments section. I hope this helps in the future.

      In the comment section at the bottom of the page, click the 'link' tab. A 'url' box will appear above the 'response' box. Copy and paste the url of the youtube page the video is found on in that box (not the embed code) and it should work. In this case, the url is http://www.youtube.com/watch?v=TMCf7SNUb-Q. This is what I did in this comment.

      Cool video, by the way.

    • 3 years ago
  • simonedward
  • J_Jammer
  • Adumbration
  • SDLN
    • 0
      SDLN  

    • "Bottlenose dolphins suffering from food shortages may be killing their sibling species to take out the competition, scientists have warned."

      This happens when population exceeds resources. Once the population thins, things settle down.

    • 3 years ago
  • jefftego
    • 0
      jefftego  

    • When are we going to stop overfishing the oceans? When people stop buying fish from sources that are not sustainable. It's very simple and the info is out there.

    • 3 years ago
  • J_Jammer
  • Neghie
  • 24French
  • shampton
  • arcticspirit
  • satanskidney
    • 0
      satanskidney  

    • The only part that concerns me is that the attacks are increasing. I knew that they attacked their young and spinner dolphins but it seems as though they're branching out. It sounds to me like they need more food and some anger management classes.

    • 3 years ago
  • shampton
    • 0
      shampton  

    • its only a matter of time before they start walking ashore and slapping us humans silly for our crimes against mammality.

    • 3 years ago
  • kewal91
  • stephenthomson
  • jade_azul16
  • Bravura
  • Girlwonder88
  • LindseyIndigo
    • 0
      LindseyIndigo  

    • Glad to hear the fact that dolphins can be mean little sods is getting some attention! SeaWorld has an awful lot to answer for... I used to work on dolphin surveys and in a whale and dolphin hospital, and we came across animals with broken jaws, broken spines and dislocations - just from fighting each other! It's scary for all the littler dolphins to think that food shortages are going to turn bottlenoses on the less robust and meaty animals - the little guys will have no chance.

    • 3 years ago
  • Smothmoth
  • Allsunday
    • 0
      Allsunday  

    • More proof that we're in trouble and that dolphins are a hell of a lot more badass than the ones doing tricks at Sea World would have you believe.

    • 3 years ago
  • EdKnowsAll
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