(Inside Science) -- You've probably experienced it: Your friends want to sit on a restaurant patio and you grudgingly go along even though it is clearly too cold to eat outside. It turns out, some fish know exactly how you feel. They will forego their own preferred temperature to stay with the group.
Many fish like to hang out in schools, because it gives them a better chance to avoid predators, and to find mates and food. But, like humans, fish are also individuals with a variety of behaviors and environmental preferences, so they often need to compromise.
Shaun Killen, a biologist at the University of Glasgow in Scotland, and his colleagues are trying to figure out how they strike that balance. “Fish in schools all behave the same way, and experience the same temperature,” he said. “How do they agree on that?”
Killen first figured out what temperature a bunch of individual three-spined stickleback fish preferred -- it turned out there was a huge range of more than 10 degrees Celsius -- and then tempted them with friends to see if they would move away from their comfort zone.
Overall the fish tended to go where the school was regardless of the temperature, but there was variation in responses depending on both the temperature and how sociable the fish was to begin with. “Some fish are completely indifferent, while others are really social,” said Killen. “They would make differing degrees of compromise to be with the group.”
In general, the fish spent more time with the group if it was close to their preferred temperature, but particularly social individuals were willing to deviate the most from their comfort zone to stay with the group at cold temperatures.
Killen also looked at whether differences in metabolic rate -- how much energy a fish uses -- had influenced their behavior. Metabolism had no direct effect on temperature preference or their willingness to compromise, but there was an indirect link. Fish with a higher metabolic rate tended to be less social. Fish with faster metabolisms need more energy, so might stay on the edge of the group to avoid competition for food, Killen said. The results are published in the journal Proceedings of the Royal Society B.
Temperature is an important environmental condition for fish because they are cold-blooded, so they take on the temperature of the surrounding water. Their body temperature has a variety of effects on how they function. Each individual fish will have an ideal temperature that will help it optimize growth, energy use and muscle activity. Being forced out of that comfort zone by the group means an individual is sacrificing its own physiological health to gain the benefits of group life. “There are a lot of potential physiological effects of spending time at the wrong temperature,” said Killen. “It's something for us to look at in the future.”
Jolle Jolles, a behavioral ecologist who studies fish at the Max Planck Institute for Ornithology in Radolfzell, Germany, said he is particularly interested in the link between sociability and the willingness to compromise on temperature. “It highlights that an important link may exist between animal physiology, personality and group behavior, a link that is rarely explored in the field,” he said. “I would be very interested to see what happens with these kinds of relationships in freely moving groups and if the preferred temperatures may drive the spatial positioning and leadership in those groups.”
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Jolles said social animals constantly need to make compromises in order to conform to a group, something that is most clear in the speed the group moves. “All individuals need to be moving at more or less the same speed to not risk splitting apart,” he said.
The same pattern of compromise is seen in many different animals, including humans. But for most social animals the stakes are much higher than just a bit of discomfort when having a beer on the patio with friends. “For animals, conforming could be the difference between life and death,” said Killen. “The cost is a lot higher in nature.”