The earmarking process takes several weeks and is only carried out at night, when it is still bright but cooler than during the day. This makes it less stressful for the reindeer and their calves. To be able to carry out the work together, the entire family switches sleep cycles, reversing night and day. Children are up and awake working and playing all night, for weeks at a time, together with their extended families and fellow herders. They nap during the day, curling up and dozing off whenever they feel like it.