Northern Ireland researchers are trying to piece together a picture of one of the most elusive known carnivores.
Females give birth to an average of three young
The pine marten is regarded as one of Britain and Ireland's rarest wild mammals.
Queen's University researcher David Tosh said he had so far only been able to find 88 recorded sightings in Northern Ireland for the past 204 years.
The mammals - once considered to be vermin - were persecuted and trapped for their fur.
By the early 1900s, the pine marten was thought to be extinct throughout much of Britain.
Mr Tosh - a QUERCUS research assistant at Queen's school of biology and biochemistry - has now secured a grant from the Mammals Trust to compile information on historical and contemporary sightings.
"I want to get an idea about the state of the pine marten in Northern Ireland because very little is known," he said.
"In the past, the pine marten was persecuted and hunted for its fur and deforestation has taken away the natural habitat it prefers.
"Northern Ireland now has the lowest proportion of forest in Europe," said Mr Tosh.
The plan now is to visit forests across Northern Ireland to detect any evidence of the mammal's presence.
The creature is thought to be prevalent in County Fermanagh, but there is little recorded about it in other areas.
"Pine martens would not attack anyone and are more likely to run away," said Mr Tosh.
"In the Republic of Ireland, there was someone who bred them in captivity to re-introduce them down south. They were re-introduced in Killarney National Park.
"They will eat anything - they love jam sandwiches, nuts, fruit, berries, birds and field mice, so they have a varied diet."
'Similarity to cats'
Pine martens, which can live up to 12 years, have dark brown fur, with a yellow patch on the chest and neck.
Their fur is short and thin in the summer, but becomes thick and long for the winter months. They have a pointed muzzle, prominent ears and a bushy tail.
Although they are frequently mistaken for polecats, as well as differences in fur colour and their bushy tails, they are significantly larger and have longer legs and large feet.
One Irish name for the mammals is "tree-cat", because of their similarity to cats.
Pine Martens will mostly eat anything
Pine martens are excellent climbers, and climb with agility in a squirrel-like manner from tree to tree.
They are nocturnal and favour refuge sites including rocky crevices, disused squirrel nests and holes in trees.
Females give birth to an average of three young, which become fully independent after six months.
They received protection throughout the UK in 1981 with the Wildlife and Countryside Act, and the subsequent amended Environmental Protection Act of 1990, which prohibits certain methods of killing the animals such as shooting.
Legislation together with reforestation has enabled the pine marten population to recover, although it is not as widespread as it once was.
"Any information I can collect will be good and will hopefully lead to more research into the pine marten in Northern Ireland," said Mr Tosh.