The islands scattered throughout Gatun Lake are in fact the summits of hills that were drowned by rising water from when the canal was first built. Some of these islands have been turned into wildlife sanctuaries following the mass congregation of animals and birds at the summits of the hills when the lake filled. The diversity of insect, animal and bird species is spectacular, as one of the engineers found out when the reservoir was still filling. While on his regular inspection of the lake he reported seeing " a half-drowned tree covered with what appeared to be black foliage." After rowing up to the tree to study it further, the engineer discovered - to his horror - that the foliage was in fact tens of thousands of tarantulas desperately trying to avoid drowning.
