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.
🐾Some heroes walk on two feet. Some leave pawprints behind.
After nearly 8 years of service, K9 Leon retires during the Independence Day celebration at @kaziranga_.
With 200+ patrols and 30+ specialised operations, he helped protect Assam’s wildlife. Thank you, Leon. @NABU_depic.twitter.com/M51hLNPZm0
— Aaranyak (@aaranyak) August 15, 2026
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.
It needs an odour.
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 vary by breed, but a dog’s sense of smell is thought to be between 100,000 and 100 million times more sensitive than that of humans. A much larger proportion of a dog’s brain is also dedicated to processing scent.
The difference is not simply that dogs can smell more. They can separate smells.
A dog can detect extremely low concentrations of an odour. Research cited by conservation detection experts compares this sensitivity to detecting the equivalent of a teaspoon of sugar in five million litres of water — roughly the volume of two Olympic-sized swimming pools.
Dogs can also distinguish between closely related odours.
Aaranyak’s dog unit was established as part of wider efforts to strengthen anti-poaching work in Assam, with support from NABU International. Photograph: (Aaranyak)
Their nostrils give them another advantage. Each nostril can analyse the air independently, allowing a dog to detect small differences in scent concentration. Those differences can provide directional information: stronger on one side, weaker on the other, helping the dog adjust its path.
Even the way dogs breathe works in their favour. The structure of their noses allows exhaled air to leave through the sides, reducing interference with incoming scents. This allows them to continue analysing odours while breathing in and out.
For a tracker like Leon, this becomes a way of reading a landscape that humans cannot.
But the nose has to learn
A remarkable nose alone does not make a wildlife sniffer dog.
Training teaches the dog what matters.
Detection dogs are introduced to target scents and taught to associate finding them with a reward, often a toy or play. This is a form of classical, or Pavlovian, conditioning: the dog learns that identifying the correct scent leads to something it wants.
Scent association can be one of the quicker parts of training. The harder work is teaching a dog to remain confident and safe in unfamiliar environments, particularly when the job involves forests, rivers, difficult terrain and long searches. For dogs that have come from troubled backgrounds, rehabilitation can take even longer.
On 15 August 2026, Leon retired from active service during the Independence Day ceremony at Kaziranga National Park and Tiger Reserve. Photograph: (Aaranyak)
The relationship with the handler is equally important.
A detection dog does not work alone. The dog searches, while the handler reads its behaviour, controls the operation and helps turn its indication into an investigation.
Leon’s career shows the power of that partnership
Leon completed a 12-month specialised training programme before joining active duty in November 2018.
During the 2019 floods, he followed a scent trail for nearly 20 km that helped investigators trace a suspected rhino poacher.
In 2023, after a deer carcass was discovered in the Bokakhat area, Leon’s tracking helped forest personnel locate crucial evidence and led them to four suspected poachers, according to Aaranyak.
Then came a case far removed from Kaziranga’s forests.
In 2025, Leon assisted Assam Police in a gold theft investigation in Golaghat town. His scent-tracking work helped investigators identify and arrest four people allegedly involved in the theft.
These cases show why conservation dogs can be useful for more than simply finding animals or chasing suspects. Their strongest contribution can be the evidence trail they help investigators recover.
A different kind of conservation tool
Wildlife crime rarely leaves a convenient trail.
A poacher may move through dense vegetation, cross water, discard an object or leave an area before investigators arrive. Animal parts can also travel far beyond forests, making their way into vehicles, markets, warehouses and international trade routes.
That is where scent detection adds another layer to enforcement.
Aaranyak’s dog unit was established as part of wider efforts to strengthen anti-poaching work in Assam, with support from NABU International. Leon was among the dogs acquired in 2017, with specialised training preparing the unit for operational work.
Leon’s retirement therefore marks more than the end of one working dog’s career. It also highlights how an ability dogs have always possessed — following a scent — can become a powerful conservation tool.
On 15 August, Leon stopped going out on patrol. Aaranyak has said he will continue to receive proper care throughout his retirement.
His working life took him through floodwaters, forest camps and riverine terrain, as well as investigations that stretched beyond wildlife crime.
Now, after nearly eight years and hundreds of patrols, his routine will be quieter.
But the trail he leaves behind is anything but.
