In the floodwaters of Kaziranga in 2019, a trail was almost invisible to the human eye.

For K9 Leon, it wasn’t.

The Belgian Malinois followed the scent of a suspect for nearly 20 km, moving across forest camps and security checkpoints. His tracking helped investigators identify and apprehend a suspected rhino poacher.

Six years later, in a very different setting, his nose was put to work in a gold theft investigation in Golaghat.

On 15 August 2026, Leon retired from active service during the Independence Day ceremony at Kaziranga National Park and Tiger Reserve.

Nearly eight years after joining the frontline, he leaves behind more than 200 patrols and over 30 specialised operations with Aaranyak’s K9 Sniffer Dog Squad, the Assam Forest Department, Kaziranga authorities and Assam Police. His handlers, Anil Kumar Das and Mrigen Das, worked alongside him throughout those years.

But Leon’s retirement also raises a fascinating question: what exactly is a wildlife sniffer dog smelling when it follows a poacher through a forest? And how can a dog’s nose find what people cannot?

The trail humans miss

A dog does not need to see a rhinoceros, a poacher or a piece of contraband to find it.

According to the IFAW-International Fund for Animal Welfare, wildlife detection dogs can be trained to identify scents associated with animal parts and derivatives, including those of rhinos, elephants and tigers. Depending on the assignment, dogs can also be trained to detect deer meat, live birds, snakes, porcupines, turtles and tortoises, as well as plant products such as red sanders.

The principle is similar to that used to train dogs to detect drugs or explosives: a dog is introduced to a target scent and taught to indicate when it finds it.

That makes dogs useful in places where conventional searches can be difficult — forests, vehicles, luggage, storage areas, shipping containers or even a trail that has long disappeared from human sight.

The work begins with the nose.

A nose built for clues

Estimates........

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