While quietly walking my small dog, we often pass houses where the dog inside, which is out of sight, begins barking. How does the dog know to bark if it can鈥檛 see, smell or hear us?
Pam Lunn, Kenilworth, Warwickshire, UK
I wouldn鈥檛 assume that the barking dog is unable to smell your dog. The houses you are passing aren鈥檛 hermetically sealed. Dogs can detect scent molecules at very low concentrations in the air.
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Peter Holness, Bengeo, Hertfordshire, UK
Canine hearing can be acute. My dog, Arby, knows the 鈥渁coustic signature鈥� of his metal bowl. A 鈥渢ing鈥� from the most minute morsel dropped in that bowl brings Arby rushing to it from any part of our house.
Adam Gray, Manchester, UK
You are probably not walking as quietly as you think. Dogs can hear frequencies up to around 60 kilohertz, far higher than our upper limit, so any high frequency noise you produce may be imperceptible to you but perfectly audible to a dog. Plus, some dogs can hear sound down to -15 decibels, much quieter than the lower limit for humans, which is 0 decibels by definition. So even if you can鈥檛 hear yourself walking, nearby dogs almost certainly can.
Steve Swift, Alton, Hampshire, UK
Our dog, Alfie, can detect the post van from about 100 metres away, demonstrating that his hearing is very much better than a human鈥檚. What I can鈥檛 work out is how he reliably detects my wife on her way home from work at a distance of 3 kilometres or more.
Tony Holkham, Blaenffos, Pembrokeshire, UK
A dog鈥檚 sense of smell is vastly superior to ours, and your approach may be detectable to the dog inside when you are quite a distance away.
The dog may also sense your footfalls through the ground, as sound or seismic waves will travel from outside to inside through any convenient conduit, such as sewage pipes, electric wiring or fibre cabling.
Dogs are also very time aware. If your walk is at a similar time each day, the barker will be expecting you and your dog, and so be alert for the other signals.
My dog, Sparky, who is almost totally deaf, is still able to 鈥渟ense鈥� the movement of people and vehicles outside. He can distinguish different people鈥檚 footsteps. He rarely barks, though, as he may well have come to presume that humans can鈥檛 hear anything, either.
Dogs are pretty smart, sensually. What is amazing is that they don鈥檛 get annoyed with us, who aren鈥檛.
Richard Woods, Halstead, Essex, UK
The behaviour of our shih-tzu, Rupert, suggests that dogs鈥� heightened senses are key to this. If I come up in the lift at our apartment block and leave the lift talking to someone, he barks from behind the closed door, 15 metres away. If I am not talking, he doesn鈥檛 bark.
He will bark at either of our daughters arriving, long before they have reached our door. But he never responds to anyone else coming out of the lift, so he must be highly sensitive, and also responding specifically to the sound of my voice. He doesn鈥檛 bark at visitors unless they come in through the door and are strangers.
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