Part of the show Climate Change & Alternative Energy
Scientists in the USA think that the annual monarch butterfly migration marathon from Canada to Central America may be keeping the species in tip top shape by reducing parasite infestations. Using the butterfly equivalent of a treadmill, scientists have found that members of the flock highly infested with parasites flew slower and tired more quickly than those with less parasites. Because migrating butterflies are known to have a lower number of parasites compared with those that don't migrate, it seems that butterflies with lots of parasites can't stand the pace and drop out of the race. By picking off the parasite-infested flyers, the gruelling migration leaves a flock of healthy front-runners that reduce the spread of infection and aid species survival.