What Scent Are Dogs Really Following in Mantrailing? The Science Behind Human and Pet Trails in Cheshire & South Manchester
- Apr 29
- 7 min read
If you’ve ever watched a dog confidently work a trail after only sniffing a scent article, you may have wondered: What exactly are they smelling? Is it skin cells, breath, sweat, or something else entirely?
At Dog Trailing UK, we run professional mantrailing sessions in Cheshire and South Manchester, where dogs learn to locate a hidden person by following that person’s unique scent.
We also run pet trails, where one dog locates another, a safely positioned hidden dog. In both activities, the dog is not simply “following footsteps” — they are interpreting a highly complex scent picture.
Understanding how scent behaves helps handlers trust their dogs, read behaviour more accurately, and appreciate just how extraordinary canine noses really are.
What Is a “Human Scent” in Mantrailing?
Human scent is not one single smell. It is a constantly changing combination of:
Skin cells (including microscopic flakes called corneocytes)
Sweat gland secretions
Skin oils
Bacteria living naturally on the skin
Volatile organic compounds (VOCs) produced by the body
Breath odours
Traces influenced by diet, health, medication, clothing and environment
Research shows that this combination creates an odour profile distinctive enough for trained dogs to discriminate one individual from another. An individual's unique DNA has no smell itself. (Sources: ScienceDirect 2018, ScienceDirect 2024).
That is why, when we present a dog with a scent article (for example, gloves, clothing, keys, or another item carrying the runner’s odour), the dog can use it as a reference sample and search for the matching scent trail.
Is It Skin Cells, Breath or Sweat?
The honest scientific answer is: all of the above, working together.
Many people assume dogs trail only skin cells falling to the ground. Skin rafts are certainly important, but they are only one part of the scent cloud. Studies indicate human scent contains thousands of volatile and semi-volatile compounds, including chemicals from sweat, sebaceous secretions and microbial activity on the skin. (Source: ScienceDirect 2024).
Breathing also contributes. Every exhalation releases moisture and compounds into the air, especially when a person is moving, talking or breathing heavily. This may help explain why fresh trails can sometimes produce a strong airborne scent.
So when your dog starts a trail, they are usually working a whole scent signature, not one isolated source.
How Can Dogs Identify the Correct Person in a Split Runner Scenario?
In advanced mantrailing, we may use a decoy runner. For example:
Two people start together
They separate at some point
The dog has only been presented with the scent article of the true runner
Yet many trained dogs still select the correct route and locate the right person.
Why? Because the dog is not merely following “the freshest human smell”. They are matching the scent they sampled at the start with the scent picture they encounter on the trail.
This ability to discriminate between individuals has been demonstrated in controlled studies, where trained dogs successfully matched scent samples to specific people and rejected non-matching odours. (Source: ScienceDirect 2018).
For handlers, this is where trust becomes vital. The dog may choose a route that looks illogical to us — but makes perfect sense through scent.
Ground Scent vs Air Scent: Why Dogs Use Both
In trailing, dogs commonly switch between ground scent and air scent.
1. Ground Scent
This is scent deposited or settling onto surfaces such as grass, soil, pavements or woodland floor.
It may include:
Settled skin cells
Residual body odour
Contact scent from shoes or clothing brushing surfaces
Localised scent pooling in sheltered areas
Dogs using ground scent often lower their nose and work methodically.
2. Air Scent
This is a scent carried on moving air currents. Dogs may lift their heads, cast wider, or suddenly pull with purpose when they catch airborne scent drifting from the hidden runner.
Research reviews note that dogs may use ground sniffing, air sniffing, or both, depending on environment, weather, training and target odour. (Source: PMC 2021).
What Determines Whether a Dog Uses Ground or Air Scent?
Several factors influence strategy:
Wind Direction and Strength
Wind can carry scent away from the runner, creating plumes or pockets. Skilled dogs often work across the wind to locate the strongest source.
Temperature
Heat can accelerate evaporation and scent movement, but very hot conditions may reduce persistence on surfaces.
Humidity
Moisture often helps scent remain available longer and may improve scenting conditions.
Terrain
Grass and vegetation often hold scent well
Tarmac and concrete can be more challenging
Woodland can create scent traps and swirls
Urban areas produce contamination from many competing odours
Trail Age
Fresh trails may offer stronger airborne components. Older trails may require more careful problem-solving and a need to focus on ground scent.
What Challenges Does Ground Scent Present?
Ground scent can be disrupted by:
Heavy foot traffic
Rainfall
Dry heat
Hard surfaces
Cross-contamination from multiple people
However, it can also remain useful in sheltered spots, vegetation, corners, gateways and surface transitions.
What Challenges Does Air Scent Present?
Air scent is dynamic. It moves, pools, lifts and swirls.
This can cause:
Overshooting the runner
Sudden directional changes
Large casting patterns
False assumptions by handlers who think the dog is “off trail”
Often, the dog is not wrong — they are solving a moving scent.
What About Ground Disturbance Scent?
Ground disturbance scent is more associated with traditional tracking than mantrailing.
This can include:
Crushed vegetation
Disturbed soil
Broken plant cells
Mechanical changes caused by footsteps
Some dogs may notice these cues, especially on natural terrain, but in mantrailing, the priority is usually the individual’s scent rather than footstep-by-footstep disturbance.
How Does This Apply to Pet Trails?
At Dog Trailing Cheshire, we also run pet trails, where one dog hides safely and another dog-handler team searches.
Dogs also have unique scent signatures influenced by:
coat oils
saliva
skin microbiome
breath
hormonal state
health and diet
Research published in Applied Animal Behaviour Science has shown that scent-based activities can create positive emotional effects and engagement in dogs, reinforcing why nose-led activities are so rewarding.
That means dogs can learn to search for a specific dog just as they search for a person.
Safety always comes first, with sufficient distance, so no direct interaction is required.
The Science of Scent Behaviour: Why Air Scenting Looks “Messy”
1. Scent Travels in Plumes, Not Straight Lines
Odour released from a person does not spread evenly. Instead, it tends to form an odour plume — irregular ribbons, pockets and filaments of scent carried by moving air.
A recent Frontiers review explains that odour movement involves:
advection (transport by wind/airflow)
diffusion (molecules spreading naturally)
turbulent mixing (chaotic swirling air that breaks scent into patches)
This creates the irregular structure often casually called a “scent cone”. (Source: Frontiers 2025)
What that means in trailing:
Your dog may encounter:
strong scent in one spot
nothing two metres later
strong scent again, further on
So zig-zagging or casting is often excellent problem-solving, not confusion.
2. Dogs Search for Intermittent Scent Signals
Research notes that dogs sample odour signals within a plume rather than continuously smelling a steady stream. Because scent and air are constantly moving, the dog receives repeated brief opportunities to detect the target odour.
Practical implication:
A dog lifting their head, pausing, circling, or rechecking an area may be trying to re-acquire the next available scent pulse.
3. Wind Can Move Scent Away From the Person
The hidden runner may not be where the scent is strongest.
Airflow around objects, trees, walls and vehicles can displace odour significantly. The same Frontiers review explains that scent signals may be present far away from the source and absent where the dog is currently sniffing close to it. (Source: Frontiers 2025).
Practical implication:
A dog may suddenly pull sideways or overshoot, then turn back. This can be correct behaviour caused by displaced scent.
4. Human Thermal Plume and Aerodynamic Wake
Humans generate their own airflow effects. Research in Frontiers in Veterinary Science describes two important mechanisms:
Human Thermal Plume
Body heat causes warm air to rise around a stationary person, carrying odour upward.
Human Aerodynamic Wake
As a person walks, air flows behind them, forming a wake that carries their scent.
The review notes that this likely influences where dogs detect human scent during search tasks. (Source: Frontiers 2016).
Practical implication for mantrailing:
A moving runner may leave:
ground-associated scent
airborne wake scent behind them
eddies of scent at corners and obstacles
This helps explain why dogs may air scent behind or beside a runner’s true path.
5. Terrain Creates Scent Traps and Dead Zones
Air behaves differently depending on the environment:
Woodland
scent pools in still areas
swirls around trunks and hedges
Urban Streets
wind tunnels between buildings
corners create eddies
traffic disturbs airflow
Open Fields
cleaner wind direction
broader scent plumes
Practical implication:
The same dog can look brilliant in one venue and more methodical in another because scent behaviour changed, not because the dog regressed.
6. Dogs Likely Use Concentration + Timing
Emerging modelling research on turbulent odour plumes suggests animals may use both:
how strong a scent is
how often scent pulses are encountered
These cues help estimate source location in unstable plumes. (Source: arXiv 2021).
Practical implication:
When your dog speeds up after brief scent hits, they may be reading the pattern of scent pulses rather than following a continuous trail.
Why This Matters for Handlers
When handlers understand scent behaviour, they stop assuming the dog is “wrong”.
What may look messy often means the dog is:
relocating scent
checking wind movement
rejecting contamination
choosing between ground scent and air scent
solving a puzzle we cannot perceive
Researchers at the University of Lincoln continue to study how working dogs perform in changing environments and how cognition affects success in operational tasks. (Sources: University of Lincoln, University of Lincoln).
What This Means for Handlers in Mantrailing
If your dog:
lifts head suddenly
casts wide
checks side roads
overshoots then returns
circles before committing
…it may indicate they are interpreting moving airborne scent, not losing the trail.
This is especially common in:
crossroads
car parks
woodland rides
building corners
windy fields
fresh trails with active air movement
Experience Real Mantrailing in Cheshire & South Manchester
Dogs do not always follow a neat line of scent. Human odour often moves through the environment in drifting plumes, pockets and scent filaments shaped by wind, terrain and temperature. Research shows dogs may detect intermittent airborne scent signals and use these to work towards the hidden person. This is why skilled trailing dogs often cast, lift their heads, or change direction suddenly — they are solving the behaviour of scent itself.
At www.dogtrailing.co.uk, we help dogs and handlers build confidence, teamwork and problem-solving through expertly designed mantrailing sessions in Cheshire and South Manchester.
Whether you are completely new or looking to progress into complex split trails, urban environments, our sessions are safe, engaging and science-informed.
Ready to see what your dog can really do?
Visit www.dogtrailing.co.uk to book your next trail and discover the remarkable world your dog experiences through scent.
Additional References
European Commission Joint Research Centre – Canine olfaction studies
University of Lincoln canine cognition research
Royal Veterinary College canine physiology resources
Applied Animal Behaviour Science
Frontiers in Veterinary Science
Forensic human scent discrimination studies
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