Observations made during five field expeditions starting in 1993 by John Hare and the WCPF suggest that the surviving populations may be facing an 80% decline within the next 30 years.
John Hare和WCPF在1993年开始的五次野外考察中所做的观察表明，在未来30年里，幸存的种群可能面临80%的下降。