By Rebecca Morelle
Science reporter, BBC News
Lying somewhere in the mountainous, snow-cloaked terrain of Pakistan's Tooshi Game Reserve is a collar that could help unlock the secrets of the elusive snow leopard.
For the past year, this piece of hi-tech equipment has sat around the neck of a wild snow leopard, recording, via the global positioning system (GPS), almost every step of her travels as she roamed the Pakistan-Afghanistan border.
And now the collar has dropped off - as it was programmed to - the hunt is under way to retrieve it and for the first time shed light on the secretive animal's movements.
For Tom McCarthy, science and conservation director of the Snow Leopard Trust, getting hold of the collar is especially important thanks to some of the technical difficulties that the project has faced over the last 14 months.
In November 2006, he and his team captured a 35kg (75lb) female snow leopard - who they named Bayad-e-Kohsaar (Urdu for In Memory of the Mountains) - in the Chitral Gol National Park in Pakistan and fitted the satellite collar.
Between 3,500-7,000 snow leopards estimated in wild
Live in high, rugged mountains of central Asia
Shy, elusive and solitary animals
Home-range is unknown
In captivity, live up to 21 years
Adults weigh between 35-55kg, and stand about 60cm tall
Pale dense fur covered in unique dark spots for camouflage
Female snow leopards mate every other year
Usually 2-3 cubs born in litter
It was the same cat that featured in the BBC's Planet Earth and more recent Natural World documentaries.
The team had planned for the collar to send a burst of Bayad's GPS location coordinates every two weeks, through uplinks to the Argos satellite system, so that they could study the collared cat's latest movements.
But a fog of background radio noise over central Asia has meant that it has had problems "talking" to the Argos satellites and the bulk of the GPS data has remained stored on the collar.
Dr McCarthy explained: "The power of the collar comes so close to breaking through that background noise, just not quite and not very often."
Technical tests on the collar carried out with a captive snow leopard in the Woodland Park Zoo in Seattle revealed that the collar had no problems uplinking to Argos outside of Asia.
The team tested the collar on a snow leopard in a Seattle zoo
The researcher added: "Through China and down to where Bayad is, it is definitely a background noise problem."
However, the team did not have to suffer total-satellite silence.
In May, a signal managed to break through, sending GPS data that revealed Bayad had moved from Pakistan to Afghanistan; in July, another uplink confirmed she had travelled to a slightly different spot in Afghanistan.
Dr McCarthy told the BBC News website: "All we are getting now is a few little blips that tell us over summer she is out in the mountains of Afghanistan, but when we see the full set of data off that collar, what it shows us could be incredible."
He estimates that the collar could hold between 500 and 1,000 GPS location coordinates, which when analysed could shed light on the behaviour of an animal that is notoriously difficult to study.
He explained: "It will not only show us her range, but it will show us how far she moved in any 8-hour period or over the course of a month, the longest single trip that she did, how long on average she sat at a kill site, or whether she got close to humans during her travels."
1: Nov 2006 - Bayad's collar fitted
2: May/July 2007- GPS uplinks reveal move to Afghanistan
3: Jan 2008 - collarless Bayad sighted in Pakistan
Recent sightings of a collarless Bayad have revealed she has now returned to Pakistan, close to where she was initially tagged, for winter; a signal from her collar shows that it can be found nearby, lying somewhere in the rocky landscape.
Dr McCarthy said: "I'm not surprised that she came back to exactly where she was last year; the BBC film crew filmed her in the same site three years in a row, so we expected her to come back.
"We even knew which day to expect her, and sure enough that was right when she turned up."
Because of political unrest following the assassination of Benazir Bhutto, Tom McCarthy has been advised against travelling to this region, so a local team are now trying to locate and retrieve the collar using VHF radio-tracking.
But heavy snowfall has so far scuppered their efforts and they are now waiting for the conditions to improve.
Loss of a friend
For the Snow Leopard Trust the challenge of finding the collar has gained even more significance following the news that wildlife biologist Eric York, one of the scientists involved in the tagging project, had died unexpectedly in November.
He had caught pneumonic plague following an autopsy on a mountain lion that had probably died of the same disease a week earlier in Grand Canyon Park, US.
Eric York who died in November was a member of the tagging team
Dr McCarthy said: "Eric was an incredible person and he had worked on so many collaring programmes and was such an asset to all of us.
"He has been a friend of mine for many years so to have this come out of the blue - one day he's with you one day he's gone - it was just a tremendous loss for all of us."
The team remain confident that they will find the collar and that the information it holds will help with the conservation efforts for this endangered cat.
Dr McCarthy told the BBC: "There are just so many basic ecological questions that you need to answer if you are going to try to design a good sound conservation programme that we don't have and the only way to get it right now is through collars.
He added: "We have also pioneered less invasive methods to learn all we can about these cats, such as automated cameras and using genetics, but certain questions are impossible to answer any other way than through collaring.
"We will soon have those answers when the collar is retrieved - if it just quits snowing!"