A rare wild tiger, nursed back to health by Nepalese vets after being injured, has been killed by poachers, a wildlife official said on Friday. The adult male tiger, which had been fitted with a collar carrying a GPS tracking system that allowed scientists to monitor its adaptation back into the wild, was killed two weeks ago, the official said. Tikaram Adhikari, a warden at Bardia National Park in Nepal\'s southern plains where the endangered animal was released, said the tiger, was last captured by the tracking system on May 9. \"For two days following that, we could not locate it. Then, early this week, we found out it had been killed by poachers,\" he said. \"The tiger was moving towards human settlements. After seeing it, the poachers offered the animal pieces of poisoned beef. It died after consuming the food,\" Adhikari said. The tiger had been named Namobuddha by park authorities. Four locals have been arrested on suspicion of poaching, Adhikari said. The tiger was captured by wildlife officials after being injured and wandering into a tourist resort in southern Nepal. It was released into Bardia national park as it was an ideal home for the animal because it of its vast size, available prey and relatively low levels of poaching, authorities said. Using the tracking system, \"we were hoping to gain valuable insights into its movement and habitat,\" Adhikari said. \"But after this incident we feel that saving the wild tigers will be more challenging.\" The project was part of Nepal\'s efforts to double its population of Royal Bengal tigers, which once roamed the country\'s southern plains in large numbers but have been depleted by poaching and the destruction of their habitat. A WWF survey carried out in 2008 found just 121 adult tigers of breeding age in the country. Experts say poverty and political instability in Nepal have created ideal conditions for poachers who kill the animals for their skin, meat and bones, which are highly valued in Chinese traditional medicine. The WWF says tigers worldwide are in serious danger of becoming extinct in the wild. During the last 100 years, their numbers have collapsed by 95 percent, from 100,000 in 1900 to only around 3,200 tigers, its says.