Research in Norway and Finland has shown that certain species of trout can decrease in length in order to conserve heat during winter. The cold-blooded marine iguana that lives in the Galapagos archipelago, can shrink by up to 20%, while other species like the juvenile brown trout decrease in size by about 10%. While this behaviour has been seen in small mammals, including shrews and lizards, in the past, this is the first study to show that this phenomenon can occur in fish.
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