IT`S not just people who watch their weight. It seems that Australia`s Goby fish do it too and the discovery is providing a whole new insight into the way animals maintain social order.

 

Marine scientists working on the Great Barrier Reef off Lizard Island have found that Goby fish deliberately diet - just to maintain their position in the pecking orders and to ensure they do not antagonise bigger Goby fish.

 

In fact according to Dr Marian Wong of James Cook University's Centre of Excellence for Coral Reef Studies, it is fear of punishment that keeps all the little Goby fish in line - particularly when it comes to mating.

If a smaller Goby male jumps the queue and goes chasing a larger Goby female, he is likely to attract the ire of a larger male. The result would be a fight and worse still, expulsion from the group.As a single Goby fish the little male is unlikely to survive long roaming the reef on his own. Therefore expulsion acts as a powerful deterrent for maintaining a stable social order."Social hierarchies are very stable in these fish and in practice challenges and expulsions are extremely rare - probably because expulsion from the group and the coral reef it occupies means almost certain death to the loser," Dr Wong said.

Dr Wong has been working on the study with an international team including marine scientists from Spain's Biological Station of Donana. Their joint paper on the discoveries has just been published in the Proceedings of the Royal Society of London. According to James Cook University the discoveries about Goby fish and the implications it has about animal social order is already creating considerable international interest.

The research paper has received a "must read" ranking from the "Faculty of 1000 Biology" which is drawn from the world's leading biological scientists.Of particular interest has been the discovery that subordinate fish deliberately diet - or starve themselves - just to remain smaller than their superiors."Many animals have social queues in which the smaller members wait their turn before they can mate," Dr Wong said."We wanted to find out how they maintain stability in a situation where you'd expect there would be a lot of competition."

According to Dr Wong, in the case of the gobies, only the top male and top female mate. All the other females have to wait their turn in a queue based on their size - the fishy equivalent of the barnyard pecking order."It is clear the fish accept the threat of punishment and co-operate as a way of maintaining their social order - and that's not so very different to how humans and other animals behave," she said.

Dr Wong said that that it had always been extremely difficult to prove experimentally how higher animals, such as apes, use punishment to control subordinates and discourage anti-social activity. It is just very difficult to observe and interpret their behaviour.

But in the case of the gobies the effect is much more apparent because they seek to maintain a particular size ratio relative to the fish above them in the queue, in order not to provoke a conflict.Dr Wong found that each fish has a size difference of about 5 per cent from the one above and the one below it in the queue.

If the difference in size decreases below this threshold, a challenge is on as the junior fish tries to jump the mating queue - and the superior one responds by trying to drive it out of the group.

"The gobies have shed new light on our understanding of how social stability is maintained in animals," she says."While it may not be accurate to draw a direct link between fish behaviour and specific human behaviour, it is clear there are general patterns of behaviour which apply to many higher life forms, ourselves included. These help us to understand why we do the things we do."