This 2 February 2019 video says about itself:
Elephants Released into the Wild | BBC Earth
In Thailand, realising elephants into the wild is one of the highest forms of making merit.
Researchers at the University of Turku found that the presence of a maternal sister was positively and significantly associated with annual female reproduction in a population of working elephants in Myanmar. In addition, an age-specific effect was found: young females were more sensitive to the presence of sisters and even more likely to reproduce when living near a sister: here.