Because when Bruce goes silent and sits down, it means he can smell explosives, or explosive materials.
The 7-year-old collie-huntaway cross and Mr Thomas, his handler, moved to Queenstown from Wellington in July.
One of three explosive detective dog (EDD) units, they are the first to be full-time at the resort's airport.
Mr Thomas said the explosive detectives had previously been stationed at the airport part-time every month during winter.
However, with the growth at Queenstown Airport - almost 34,000 international passenger movements in November - and ‘‘everything that's going on around the world'', Aviation Security (Avsec) decided it was time to appoint a full-time explosive detective unit in the resort.
The Queenstown unit covers every international outgoing flight in the resort, as well as in Dunedin, searching car parks, navigation facilities, unattended cars, items or bags, cargo and aircraft.
They also conduct random searches around the airport, at check-in counters, screening points and gate lounges.
Mr Thomas said the training for the dogs was extensive and each one was being assessed ‘‘right up until the day it graduates''.
Some go into foster homes as puppies, while others are given a second chance at life.
The Queenstown unit has formed a relationship with Dog Rescue Dunedin, which rescues dogs from Animal Control and cares for them until they find their ‘‘forever homes''.
Mr Thomas said if that organisation found a dog with potential to become an EDD, the assessment process began.
‘‘If we're in the situation where we've got room for a dog to come into the system, we'll go and assess them.
‘‘If we think it's potentially any good we'll bring it back to Queenstown and do an assessment in the airport environment for up to two weeks. We give it a really good chance.
‘‘[We] assess the dogs being around lots of noise and stuff like that.
‘‘After that we go back and say we're really keen to keep a dog and we bring it into the system.''
For foster families, everything the dog needs - including bedding, food and vet bills - is covered by Avsec, on the understanding at some point, if the dog is suitable, it will go into a 10-week training course at the Police Dog Training Centre in Upper Hutt.
However, if at any point along the way the dog was found to be unsuitable, the foster families were given first option to adopt it.
‘‘It always goes to a good home. That's our No1 priority.''
Dogs went into the training course, delivered by Avsec and the New Zealand Police, when they were typically between 1 and 2 years old.
Training involved searching and finding explosives in different environments, and teaching the dogs ‘‘passive indication''.
‘‘They're not allowed to touch and they're not allowed to bark [when they find anything].
‘‘They just sit, quietly. You can imagine if they nudged it [a bomb], or kick it with their paw.''
At the end of the course the teams are tested and certified by the police.
A passing grade means the teams graduate as ‘‘operational'' and go to work in Auckland, Wellington, Christchurch or Queenstown.
Mr Thomas said it was critical that the dogs saw work as ‘‘the fun place''.
‘‘You don't treat them as pets, because you can't afford to.
‘‘When they come to work, they need to work.
‘‘If you treat home as a place to have fun, they see home as the place they want to be. When they go home, that's their time to rest.''
Typically dogs were retired from the system when they were about 7 and began to lose agility. Again, finding a good home was the priority, giving the dogs a chance to enjoy life as a pet.
