He was a fixture in Kenya’s wildlife scene, an eccentric American with a shock of white hair, known for meticulous work on the black-market prices of ivory and rhinoceros horn. Now he is the victim in a murder mystery.

The victim, Esmond Bradley Martin, was found dead in his home in Nairobi, Kenya’s capital, on Sunday, with a stab wound in his neck.

It is not clear if Mr. Martin, who was in his mid 70s, was killed in connection to his strident views or his work. No doubt he had made many enemies, writing report after report that exposed the depth of the ivory and rhino horn trade across the world that has killed tens of thousands of endangered animals. His death sent shock waves through East Africa’s wildlife circles.

Kenyan police officials said they had yet to identify any suspects. Their leading theory is that Mr. Martin was killed in a robbery.

For decades, Mr. Martin studied ivory and rhino markets, his passion hardly fading with age. He called me incessantly in recent months, asking me to write about his latest findings from Vietnam.

When I went over for lunch at his house in the Karen neighborhood of Nairobi (named after Karen Blixen, who wrote “Out of Africa”), he made sure I left with a full stomach — and an armload of reports.

“Make sure you read ’em!” he shouted.

(I got through a few, which were full of charts, figures and fastidiously labeled pictures.)

Mr. Martin, who once served as a United Nations special envoy on rhino conservation, was considered a true expert on the ins and outs of the ivory and rhino horn trade, with deep contacts among traders, carvers, their families and other researchers.

His work “would have exhausted a man half his age,” said Iain Douglas-Hamilton, an elephant researcher and friend of Mr. Martin’s for 45 years.

The Kenyan police said Mr. Martin appeared to have been stabbed by an intruder.

But it was hard to fathom why any intruder would have perceived Mr. Martin as a physical threat. He was built like a tall vase: thin and delicate, his skin almost translucent.

Friends said he had just returned from a stroll on Sunday afternoon. His wife, Chryssee, who wrote reports with him, was out at the time. When she returned, she found Mr. Martin slumped on the floor with a deep stab wound in his neck and the family’s safe open and empty.

“He’s totally harmless and I’m sure he didn’t put up any resistance,” said Daniel Stiles, a wildlife researcher in Kenya who worked closely with Mr. Martin. “His last minutes must have been really, really awful, and he didn’t deserve to die like that.”

Nairobi has a reputation for crime. Most nice houses have high walls and countless locks. Years ago residents nicknamed the city “Nai-robbery.”

Mr. Martin arrived in Kenya in the 1960s, the son of a rich family from New York, Mr. Stiles said, after having studied geography at the University of Arizona and in Liverpool.

“Esmond changed the way we did investigations of the wildlife trade,” Mr. Stiles said. “He brought that whole quantitative element that helped get the public’s attention.”

His work, which focused on prices, weights and trading mechanisms for ivory and rhino horn, might have seemed dry, but Mr. Martin was hardly boring. He cut a dapper figure, making the rounds of cocktail parties in snug-fitting three-piece suits with brightly colored silk handkerchiefs jutting from his breast pocket.

His hair was long and unruly and perfectly white, sitting atop his head like a giant cotton ball. He threw himself lavish birthday parties with belly dancers; sometimes he appeared in a cape.

“He came across as an eccentric but I grew to deeply respect him,” Mr. Stiles said.

Several fellow conservationists said it was Mr. Martin’s clear data that had helped persuade Western and Asian governments to take a harder look at the ivory and rhino horn trade, responsible for one of the most destructive bouts of poaching in modern times.

Economic growth in China and Vietnam has created an enormous demand for ivory carvings and rhino horn powder (which many Vietnamese believe has special medicinal properties).

“Esmond was one of the most sincere, honest and dedicated people I ever knew,” Mr. Stiles said. “He was always more interested in producing facts than building up his own reputation.”