Conservationists are overestimating the number of species that have been driven to extinction, scientists have said。

　　A study has found that a third of all mammal species declared extinct in the past few centuries have turned up alive and well。

　　Some of the more reclusive creatures managed to hide from sight for 80 years only to reappear within four years of being officially named extinct in the wild。

　　The shy okapi – which resembles a cross between a zebra and a giraffe – was first discovered in the Democratic Republic of Congo in 1901.

　　After increasingly rarer sightings, it vanished from the wildlife radar for decades from 1959, prompting fears that it had died out。

　　But five years ago researchers working for the WWF found okapi tracks in the wild。

　　Other mammals 'back from the dead' include the rat-like Cuban solenodon, the Christmas Island shrew, the Vanikoro Flying Fox of the Solomon Islands, the Australian central rock rat and the Talaud Flying Fox of Indonesia。

　　The revelations come as the world's leading conservationists prepare for a major United Nations summit on biodiversity in Nagoya, Japan, next month。

　　Many scientists believe the world is going through a new 'mass extinction' fuelled by mankind – and that more species are disappearing now than at any time since the dinosaurs vanished 65 million years ago。

　　According to the International Union for the Conservation of Nature, 22 per cent of the world's mammals are at risk of extinction. In Britain, more than two plant and animal species are being wiped out each year。

　　科学家称，环保人士对灭绝物种的数量估计过高。

　　一项研究发现，过去几个世纪已经宣告灭绝的哺乳动物中有三分之一其实都活得好好的。

　　有些行踪更隐秘的生物在消失了80年后被官方宣告已在野外绝种，而在宣告后不到四年，它们又再次现身。

　　害羞的欧卡皮鹿是外形界于斑马和长颈鹿之间的一种动物，1901年在刚果民主共和国首次被发现。

　　后来，人们见到它的次数越来越少，从1959年起野生动物雷达系统就再也捕捉不到它的踪迹，于是人们担心它已经绝种了。

　　然而，五年前，为世界野生动物基金会工作的研究人员在野外发现了欧卡皮鹿的踪迹。

　　其他“死而复生”的哺乳动物包括外形像老鼠的古巴鼩、圣诞岛麝香鼩、所罗门群岛的瓦尼科罗狐蝠、中澳岩鼠，还有印尼的塔劳狐蝠。

　　这些真相是世界知名的环保人士们为联合国关于生态多样性的一次大型峰会做准备时发现的。该峰会将于下个月在日本名古屋举行。

　　许多科学家认为世界正在经历由人类引发的新一轮“物种大灭绝”，现在灭绝的物种是自6500万年前恐龙灭绝以来最多的。

　　据世界自然保护联盟称，世界上22%的哺乳动物正面临绝种的危险。在英国，每年消失的植物和动物物种都在两个以上。