Juba - All sides in South Sudan's civil war have slaughtered wildlife including elephant, giraffe and antelope, conservationists said Thursday, warning huge efforts must be made to protect the surviving animal population. In a report released on World Wildlife Day, conservationists said gunmen had devastated one of Africa's largest animal migrations, becoming yet another victim of an ongoing civil war marked by atrocities in which tens of thousands of people have been killed.The US-based Wildlife Conservation Society (WCS), which backs government efforts to protect its natural resources, warned of an "alarming expansion of illegal exploitation and trafficking". It said there had been a "sharp rise" in recent months of commercial bush meat poaching of antelopes, elephant killing, ivory smuggling, logging of trees, charcoal production and gold mining, damaging formerly pristine forests.Elephants have been slaughtered for their tusks, while giraffe and antelope have been mowed down with machine guns for meat to feed the tens of thousands of soldiers and rebels battling each other since December 2013. "The various armed forces across the country have been implicated in cases of large-scale wildlife poaching, both for consumption and commercial trafficking," WCS said, adding that "international actors" were also believed to be involved.Eastern regions are home to giant herds of antelope - including tiang, white-eared kob and reedbuck - as well as giraffe, lion, cheetah and vast bird populations.Gloomy assessmentThe wilderness is the largest area of intact savannah eco-system left in east Africa, and in terms of numbers, the circular migration of animals rivals that of Kenya's iconic Maasai Mara and Tanzania's Serengeti ecosystems."There is cause for great concern for many vulnerable species in the country, particularly elephant, giraffe, and tiang populations," WCS said. In a , it said ongoing surveys had confirmed "that some of these wildlife populations have managed to survive in some areas"."There is still hope to protect these populations and halt the expanding poaching and trafficking pressures," WCS added.The report comes a day after the United Nations warned that the country's humanitarian crisis is worsening, with the warring sides "dragging their feet" in implementing an August peace deal.