'When I lobbed logs into my trailer, she went berserk'

When working with a chain saw, it is as well to concentrate. Two occasions on which I let my mind wander stand out in my memory with disconcerting clarity. On one, I felled a witch elm on to my own trailer, and almost on to my wife; on the other, I let the chain touch the inside of my knee - which meant immediate evacuation to hospital.

I was therefore keeping my wits about me the other afternoon as I cut into a pile of tree-tops that a farmer had dragged out into a field. Suddenly, I became aware that something had passed close behind me at high speed. Taking my finger off the throttle trigger, I looked round. There was Cindy, the sheepdog from the farm, coming in fast at an angle on another run.

I was glad to be wearing boots with high, padded ankles. On her regular beat, outside the farmyard, Cindy makes it her duty to give the bum's rush to any vehicle passing along the lane. From her favourite ambush- point at one corner of the barn, she hurtles out, barking furiously, and races beside the car, snapping at its wheels.

Visitors on foot are no more welcome. Even when I enter into friendly conversation with her owner, she gives off menacing growls. Although wagging her tail, she looks as though she may sink her teeth into me at any moment. When riding in his pick-up truck, she is aggression personified.

What, then, were her motives in making these high-speed passes in the field? Rather than risk having jaws close on my achilles tendon, I stopped the saw, took off my helmet and made overtures.

Off her own territory, Cindy was a different animal. She wagged her tail, licked my hand, allowed me to chuck her under the chin, frisked about and generally made herself agreeable. Yet when I began to lob logs into my trailer, she went berserk, racing in circles, leaping high into the air, and uttering strangled howls as each missile fell out of her reach. Clearly, she wanted action, and in particular sticks thrown for her to chase.

I chose a thin piece of wood and flung it. She went after it like smoke, pounced, gnashed, tossed it into the air and abandoned it - as if it was a rat and she was saying, "There you are, that's how I kill 'em." A couple more sticks received similar treatment. Immediately after she had dealt with each one, she came tearing back for the next.

But then, as a longer branch landed on the grass, she did not shake it or throw it about. Instead, she seized it and bore it off in her mouth, galloping the whole way home. Two, three, four hundred yards up the field she went, until she squeezed under the gate and disappeared towards the farmyard. Ten minutes later she came back - and this time there was no fooling about. The first stick I threw found favour: she picked it up and sprinted for base. "Good God!" I thought. "Have they trained her to bring home firewood?"

Inquiries revealed that they had done no such thing: the sticks had not reached the farm. They must have gone into some secret cache. I was left reflecting on how difficult it is to discern animals' motives, and how dangerous it can be to take good temper for granted.

Few creatures can have been more deceptive than our champion ram, Agamemnon - that arch destroyer of fence-posts. It is true that his final preparation for a charge - three steps backwards and one to the side, like a rugger player lining up for a place-kick - always gave him away at the last moment; but even when he was harbouring the most dastardly thoughts, the expression on his face never changed, and only someone who knew him well could divine that if he started to lick his lips or wag his tail, it was time to watch out.

So with Cindy. We may have become buddies in the field, but I still believe that if I took any liberties on her home ground, she would bite me to the bone.