The loss of their natural habitats has caused Asian elephants to start engaging in behavior never previously recorded – forming the world's scariest all-male teenage gangs.

Elephant herds are normally matriarchal, consisting of adult females and young. When males are old enough to leave they become largely solitary. However, the conversion of most of their former habitat to farms has forced changes, and adolescent male elephants are forming gangs, increasing the threat of conflict with humans.

As the land allocated to wildlife around the world shrinks, many animals stray into human-occupied spaces to survive. In some places, this may involve intrusions by raccoons or possums, but in southern India, the visitors are on a larger scale. Nishant Srinivasaiah of India's National Institute of Advanced Studies collected 1,445 photographs of elephants over a 23 month period to see how their behavior is changing in the face of human modification of the environment.

As they have done for millions of years, the region's juvenile elephants live in mixed-sex groups, Srinivasaiah found. Sexually mature males keep primarily solitary lives except when looking to mate. However, in Scientific Reports Srinivasaiah has shown that in-between, the males' lives diverge depending on their habitat.

In forests, the males usually live on their own between the ages of 11 and 20, but in agricultural areas, they form groups of averaging four and a half. Smaller groups develop in semi-forested areas. Like humans, male elephants of that age experience a lot of hormonal changes that make them unpredictable enough on their own, let alone collectively.

Residents have been reporting groups of males wreaking havoc on their farms for some time, but Srinivasaiah has shown these are not random associations brought together by all smelling the same feeding opportunity. Rather these are stable collections of males who stay together for long periods of time – more than 10 years in one case.

These groups forage on agricultural crops six times as often as female-led groups. Srinivasaiah and co-authors describe this as a “high-risk high-gain foraging strategy”. It gives the males access to richer food sources than they would get elsewhere, allowing them to improve their body condition quickly, potentially setting them up for future mating opportunities. On the other hand, the consequences for farmers can be devastating, and humans seldom take such things lying down. Almost 150 elephants are known to be killed by humans in India each year, a major threat to a numerically small population.

Everything with elephants happens at a larger scale, but the paper points out this is indicative of mammals “Coping with large-scale changes in their environment...through behavioral flexibility rather than commonly discussed genetic adaptations.” Similar behavior has already been recorded among African elephants, but was unknown in the area of India that Srinivasaiah studied even 20 years ago.