IT was typical of the quiet illustrator David Green that he never drove. The long-haired conservationist, who had respect for all living creatures, was afraid that he might run something over, even an insect, and kill it.

Speaking from the house in Darlington she shared with her son before he was shot and killed in India on Thursday, his mother Edna, 85, recalled that Mr Green never owned a car.

"He didn't ever want to kill anything. He would have hated to have killed even insects, so he walked everywhere - up to 15 miles a day," she said.

It was the same kindly, steadfast principles that were evident throughout his life, from launching a successful campaign to save the lives of frogs at his local pond or caring for animals in his work as a zoo keeper.

Mr Green started work in the printing department at Patons and Baldwins factory, in Darlington. It was a job he hated and it was not long before he secured a job as a zoo keeper at Whipsnade Zoo, Bedfordshire, looking after the big cats.

He left Whipsnade when bosses objected to the length of his hair, but secured a job at Manchester Zoo, where no one seemed to mind his locks.

Mr Green returned to his native North-East when he was in his late 20s to study at Teesside College of Art, later teaching the subject in Sunderland.

Later, his interest in nature, and particularly amphibians, took over. He bred frogs, newts and toads in the back garden of his home in Willow Road, Darlington, during the late 1970s and early 1980s.

The Northern Echo helped publicise his campaign to help frogs at Brinkburn pond, where many were being killed by children. He found scores of people willing to adopt tadpoles in his quest to save the species.

He later became amphibian conservation officer for Durham Conservation Trust.

At the time, he said: "Everybody cares for badgers, hedgehogs and little furry animals, but are not so interested in the less nice-looking animals. I can't understand this - those interested in nature should be interested in all its links."

Mrs Green said her son took many of his beliefs from Buddhism, often meditating twice a day.

"He liked to be quiet, he was a very gentle person", she said.

He also had the respect of conservationist Dr David Bellamy, of Bedburn, near Hamsterley, County Durham.

Dr Bellamy said: "David Green's illustrations were second to none, but he was first and foremost a natural historian and one of the best," he said.

Cliff Evans, secretary of the Darlington and Teesdale Naturalist's Field Club, had known Mr Green for 20 years and regarded him as a free spirit.

"His work was meticulous," he said. "He was well-known at all of the natural history groups in the town, but he did not belong to any of them.

"He would not have given talks, he would have hated that, but he had an awful lot of knowledge and you could chat with him, one to one, for hours."