Juveniles tend to remain in warm nursery areas.[5] In New Zealand waters juveniles can be found over the inner shelf around the North Island and around the upper South Island.[11] Separate populations with different life history characteristics apparently exist in the eastern Pacific and western Indian Ocean and possibly elsewhere; this species is not known to make transoceanic movements.[3] In the northwestern Indian Ocean, males and females segregate by location and depth during the pupping season from January to May.[9] Analysis of mitochondrial DNA has revealed substantial regional genetic variation within common threshers in all three oceans.