By Sandra Teoh and Louisa S Ponnampalam, 9th September 2026
It began as another routine survey in Langkawi’s calm, emerald waters, where we were greeted by a group of Indo-Pacific humpback dolphins. With cameras ready, we tracked and photographed their dorsal fins as they surfaced and disappeared in a regular pattern, for photo-identification. Around thirty individuals moved together, travelling and socializing closely, their breaths rising and falling in sync. One dorsal fin stood out; its shape was different. When the dolphin surfaced again, we saw a dark, rigid ring wrapped tightly around its body, cutting into its flesh at the anterior base of the dorsal fin. We later identified it as part of a discarded boat engine fan belt, and so we named the dolphin “Fanbelt”.
As we followed the group over the next hour, we noticed that Fanbelt lingered at the edges, always alone, while the rest of the dolphins remained tightly grouped. There was no visible interaction, no synchronised movement, just distance. At the time, we could only watch and record, unsure whether what we were seeing was coincidence or something more. That sighting was in 2017. Fast forward to 2019, and we spotted Fanbelt again—an encounter that brought us relief and absolute delight! After failing to resight Fanbelt in 2018, we had feared it may not have survived its grave injuries. But this time, the ring was gone and Fanbelt was no longer distant, moving within the group, surfacing and travelling alongside other dolphins. Fanbelt’s story serves as a stark reminder that human impacts extend beyond physical injury, quietly reshaping and altering how animals associate and interact, particularly within dolphin societies.
“Fanbelt” in 2017, sighted with a discarded boat engine part tightly wrapping its body, cutting into its dorsal fin and causing wounds on both sides of its body. Photo: The MareCet Research Organization.
Encounters like this are exactly why long-term monitoring of highly mobile marine megafauna is so important. Since 2010, The MareCet Research Organization has conducted marine mammal research and conservation efforts around the Langkawi archipelago, later expanding to the adjacent Perlis–Kedah mainland coastal waters in 2016. Located at the northwesternmost region of Peninsular Malaysia, these waters sit at the interface between the Andaman Sea and the Straits of Malacca. The region was recognized in 2019 as an IUCN Important Marine Mammal Area (IMMA) for several marine mammal species, including Indo-Pacific humpback dolphins.
Photo-identification boat-based survey in Langkawi—a non-invasive method used to identify individual dolphins based on unique dorsal fin features, as part of long-term monitoring efforts. Photo: The MareCet Research Organization.
This designation reflects what long-term monitoring efforts in the region have revealed. After over a decade of fieldwork, we have learnt that these waters support a significant population of Indo-Pacific humpback dolphins and serve as important feeding and nursery grounds for the species. However, their coastal distribution places them in close proximity to human activities, exposing them to multiple threats such as reduced prey due to overfishing, bycatch, propeller strikes, and marine pollution. These incidents have become increasingly frequent in recent years, and we are witnessing it firsthand.
A mother and calf pair of Indo-Pacific humpback dolphins, highlighting the close bonds and care that are central to their social structure. Photo: The MareCet Research Organization.
In our new paper, recently published in Oryx, our findings not only challenge previous assumptions about humpback dolphin group size, but also provide a rare glimpse into how these dolphins structure their social relationships. One of the most important takeaways from the paper is that the dolphin population in our study area forms a single, connected conservation unit. It means we cannot think of dolphins in Langkawi and the adjacent Perlis-–Kedah mainland coast as separate groups. Understanding their social structure is crucial, as it is shaped by key ecological and social factors such as food availability, predator–prey dynamics, and social needs, all of which can be easily disrupted by human activities. As a case in point, Fanbelt, who spent time on the edge of the group while injured and hampered by a foreign marine debris object, showed us how human impacts can influence a dolphin’s interactions and its position within the population’s social network. Mapping and recognizing these social links provides the foundation for informed management, helping us identify which individuals or relationships are most vulnerable, and ensuring that efforts protect not just dolphin numbers, but the social fabric that keeps the population connected.
What does this mean for conservation?
Conservation is not just about drawing important habitats on a map. It also requires a good understanding of the dolphins’ social structure and relationship dynamics, such as the roles individuals play within their dolphin society, how information flows amongst them, how these social links help maintain population stability and what happens if human activities disrupt those connections. Protecting the connections between individuals is as important as protecting the habitat they rely on. Our findings show that the humpback dolphins maintain a rather resilient social network, which helps them cope with change. In our field site, change is the only constant, as tourism booms and the interest to develop never ceases, thus the ability to be resilient and cope with change is tantamount to the animals’ long-term survival. However, even that resilience has its limits. That is where conservation needs to focus next, going beyond the conventional thought approaches. Conservation needs to include the mitigation of threats that impact not just individuals, but the ties and connectivity that hold the population together, even if working through wildlife behavioural data is not everyone’s cup of tea. Recognising that fact, we proposed some measures in our paper, including implementing boating best practices, establishing speed limit zones, and protecting and/or better managing critical habitats or movement corridors that facilitate social interactions and bonding for the dolphins.
Langkawi is one of the top tourism destinations in Malaysia, yet there are not currently any boating guidelines that are established to ensure safe manoeuvring of boats around frequently encountered marine wildlife such as dolphins and porpoises. Speeding, getting too close or moving directly in the dolphins’ path can lead to propeller strikes and disrupt their natural behaviour. Photo: The MareCet Research Organization.
Ultimately, in MareCet, our work promotes species conservation and habitat protection to ensure long-term survival of marine mammals in this fast-developing biodiverse region. Insights from our recent paper provide a strong evidence base for these efforts, helping ensure that our conservation actions are targeted and grounded in the latest science. We do this by translating science into actionable conservation recommendations, such as informing policymakers and decision-makers to influence marine conservation strategies, conducting outreach and education programmes among school children and the general public, and empowering local communities to become champions and stewards of the marine environment.
MareCet engages with policy makers and local stakeholders, using insights from research to promote responsible boating practices in Langkawi. Photo: The MareCet Research Organization.
To learn more about our research and conservation efforts, you can visit MareCet’s website and social media pages.
The article ‘Social structure and ‘situationships’ in Indo-Pacific humpback dolphin Sousa chinensis societies in north-western Peninsular Malaysia: conservation implications within an Important Marine Mammal Area is available open access in Oryx—The International Journal of Conservation.
