Science and nature reporter, BBC News
A female Indian rhino and her calf have been killed for their horns in Kaziranga National Park, India.
The Kaziranga rhinos had been featured in a recent BBC series
The female survived for 35 hours after the attack, but slowly bled to death after her horn was sawn off and she was shot twice by poachers.
The region's rhinos had recently featured in the BBC's natural history series Saving Planet Earth.
Despite best efforts by conservation groups, and increased funding, poaching has recently escalated in the region.
Dr Bibhab Kumar Talukdar, from Aaranyak, a conservation charity based in India, told BBC News: "The vet tried to save her but it was not possible.
"It is the first time I have seen a rhino struggle to survive for 35 hours after having their horn sawn off."
The attack took place under the cover of darkness on 19 January. The next morning the female was found in a critical condition. She struggled to survive until 21 January.
Animal ambassador David Shepherd said: "Can man, the most lethal animal on the planet, sink any lower in depravity just to make money?
"In 50 years of conservation, I have seldom seen such a sickening example of wildlife abuse. I love rhinos and they deserve a better fate than this."
Mr Shepherd is the founder of the David Shepherd Wildlife Foundation (DSWF), which supports Aaranyak in its mission to protect the Indian one-horned rhino (Rhinoceros unicornis) in Kaziranga National Park.
Melanie Shepherd, from the DSWF, told BBC News: "Between 1998 and 2006 rhino poaching in Kaziranga was brought under some control.
"However, last year poaching increased at an alarming rate, with 20 rhinos killed. Despite increased funding, there have already been four deaths in 2008." Ms Sherpherd suggests poaching has escalated in the region as the market for rhino ivory has increased in China, for use in traditional Chinese medicine and because the location of Kaziranga National Park makes it particularly vulnerable and difficult to patrol.
The park is situated in the far eastern state of Assam, close to the Chinese border.
"Kaziranga National Park is a key pivotal area. Assam is on the doorstep of the consumer market. It is easy for poachers to get across the border and then into China, Thailand, and Myanmar. The park is an obvious target," she says.
Another problem is that the Bhamaputra river makes up the Northern park boundary and is currently exploited by poachers to gain access to the park, especially in the monsoon season.
Numbers have increased from 200 in 1900 to about 2,500 today
Rhino horn, kilo-for-kilo, is five times more valuable than gold
Rhinos can reach speeds of 55km/h (35mph)
Males mark their territory with dung piles measuring up to a metre high
Indian rhinos have scent glands on their forefeet, and leave scent trails for other rhinos to smell
However, it is hoped a patrol boat, funded by a £62,000 donation from the BBC Wildlife Fund after Kaziranga's rhinos were featured on the BBC's Saving Planet Earth series, will help provide extra reinforcement to this problem.
The money is also going towards the ongoing project, started in 1995, of equipping the 400 park rangers with radios so they can report poaching incidents and call for reinforcements.
The conflict between rangers and poachers has claimed the lives of 60 people over the past 20 years.
Ms Shepherd says: "Bibhab and his team do the most amazing work fighting against sophisticated, well-armed, criminal gangs.
"Despite losses, including his second in command who was killed in action, they never give up. The Indian rhino's future lies in their hands and we must continue to support them."
The world population of one-horned Indian rhino is estimated to be 2,500 animals, three-quarters of these are found in Kaziranga National Park. The species was once found throughout the northern Indian sub-continent, but can now only be found in India and Nepal.