Understanding Sumatran Elephant Bull Behaviour in the Wild.

Deep in the heart of Sumatra lies the Leuser Ecosystem, one of the last strongholds for the Critically Endangered Sumatran elephant (Elephas maximus sumatranus).

Unlike the open grasslands of the African savanna, observing wild elephant behaviour here in the dense Southeast Asian rainforest is a difficult and arduous task.

The herd with a newborn, sighted from the treetops.

The Leuser Ecosystem offers thick vegetation, rugged terrain, and low visibility, making it one of the most challenging places in the world to study wild elephants.

Yet, through the diligent work of the Sumatran Ranger Project (SRP), we are able to gain valuable insights into the lives of these bull elephants every time they’re spotted on patrol.

As of 2025, here is a brief overview of what the scientific community already understands about the behaviour of Asian bull elephants.

Coming of Age

Bull elephants live dramatically different lives from their female counterparts. Female calves are born into a matriarchal herd and remain with their natal group for life. Males, however, are on a different path.

When a male calf is born, he stays with the natal herd through childhood and adolescence, usually until he's about 10 to 13 years old. At that point, the females strongly, and sometimes aggressively, signal that it’s time for him to move on, and he is no longer a responsibility of the natal herd.

A young bull who has freshly lost the company of his natal herd, despite popular assumptions, does not immediately become a lone wanderer. In fact, juvenile males have much to learn, and in order to have a successful coming-of-age journey, the first milestone they must complete is finding an older male who will accept and tolerate a young companion.

These mentorships between an older bull and a young bull are vital. Young bulls shadow mature males, forming loose, semi-social bachelor groups where they learn essential social and survival skills. By this stage, juveniles already understand the basics, like foraging, navigating terrain, and skin care (a surprisingly important daily ritual for elephants). What they still lack is social finesse, especially the cues, body language, and restraint needed to function as adult bulls within elephant society.

A bull visiting a baby elephant.

Musth and Maturity

Once a bull matures, typically around his late teens or early twenties, he enters a dramatic new phase of life: musth.

This periodic state of elevated testosterone is marked by distinct physical and behavioural changes, including temporal gland secretion, urine dribbling, and increased assertiveness.

During musth, bulls seek out oestrous females and may engage in tense standoffs or even sparring matches with rivals. These confrontations are rarely fatal; more often, they’re displays of dominance that determine mating rights.

A bull who has successfully learned from his elders is far better equipped to navigate the complex interplay of aggression, strategy, and social signaling that musth entails.

Communication and Intelligence

Sumatran bull elephants possess sophisticated communication skills, ranging from deep rumbling vocalizations to body movements and even seismic signals, vibrations transmitted through the ground that can travel long distances. Observations throughout Southeast Asia suggest wild bulls are intelligent and curious, capable of creative problem-solving.

For instance, bulls have been seen manipulating obstacles and bypassing electric fences by using a branch as a tool to ground the charge, behaviours that demonstrate not just instinct, but learned knowledge likely passed down through generations.

A Sumatran Ranger Project ranger patrolling through dense rainforest.

Sumatran Ranger Sightings

The villages located on the outside of the Gunung Leuser National Park are built on land well-suited for human activity.

These villages that the SRP Rangers grew up in, and now are employed to protect, are positioned along the river adjacent to the National Park as a way for the humans to access fresh water.

These communities are also built within landscapes with sparse trees that are easy to travel through. Most importantly, these villages operate on land with plenty of open fields to cultivate for their agricultural needs.

That being said, Asian elephants also prefer to inhabit land that offers similar features and functions. Elephants like land that has an accessible river for bathing and drinking, sparse trees to easily travel through, and plenty of food to sustain a large herd.

A pathway through the forest created by elephants.

This overlap in preferences means that these villages deal with a high frequency of visiting elephants, requiring the Rangers to provide assistance, resources, and the appropriate tools to these communities to support coexistence.

Since its formation in 2016, the Sumatran Ranger Project has been able to not only prevent and assist with human-elephant conflict but also have a deep record of elephant sightings in the area since 2016.

More often than not, Rangers are recording the aftermath of elephants, as elephants leave a plethora of evidence indicating that a herd or bulls have recently been in an area.

The Sumatran Ranger Project has almost a decade's worth of research on one particular herd and is the only organization in the area (Langkhat District) studying Sumatran elephant behaviour in this way.

Some signs of elephant activity include: the smashed pathways created by a herd of elephants on the move, dung, trees that have been pushed over for foraging, and footprints in the mud.

Exercising caution is paramount when observing elephants in the wild. The Rangers do not get close, as this could be deadly. If they hear a herd approaching, they climb into the trees to get out of the way, allowing the herd to pass under them without harm to the Rangers or the animals.

Sumatran Ranger Project Rangers on patrol in the rainforest.

The Herd

The Rangers have been recording data consistently from a specific herd of Sumatran elephants consisting of 14 individuals, the latest of which was born in November 2024. Elephant herds often travel long distances to find resources. However, this area seems to have everything this one herd needs and is often seen raiding local smallholder oil palm plantations.

In addition to this particular herd of 14, the Rangers also frequently see two satellite groups, each consisting of one mature male and its young bull companion. There is a mature bull that the Rangers have named Bengang, who allows a young bull to shadow him. The other mature male has been named Putung, and he has a young bull that never leaves his side, named Ogut.

In November 2024, not long after the new baby was born, the Rangers came across the large herd (females and offspring) and noticed something was different this time. They spotted Putung and Ogut mingling amongst the ladies! This was a special observation as it confirmed that the females do happily socialize with their former bull offspring (Ogut), even after forcing them to leave the group. It is unclear if Putung is also part of this same herd or if he ventured here from another part of the forest for breeding purposes, but he very well could have been visiting with his own offspring (the newest baby).

In a rainforest as dense and secretive as Leuser, every elephant sighting is precious.

Thanks to the dedication of The Sumatran Ranger Project, our knowledge of bull elephant behaviour continues to grow, one patrol at a time.

These insights not only reveal the remarkable complexity of elephant lives but also inspire a deeper commitment to protecting their future.