BARRO COLORADO — ^INGLES 363 



rapidly and its entwining roots sent out many laterals to embrace 

 its hosts and eventually to choke them to death. 



Only a few feet from the strangle!* fig stands a stilt palm. This 

 remarkable tree may be less than 6 inches in diameter and yet it 

 extends its leafy crown 60 to 70 feet out into the upper canopy. But 

 what enables a stilt palm to stand up? From the lower part of its 

 slender trunk many bracing roots grow out several feet above the 

 ground. Thus the strangler fig and the stilt palm solve in different 

 ways their problems of getting up into the light. 



Under the stilt palm across the dark forest floor a column of army 

 ants moves along swiftly. These ants represent one of over a dozen 

 species found on the island and have been studied for many years 

 by Dr. T. C. Schneirla, of the American Museum of Natural His- 

 tory. The raiding columns of these ants catch, kill, and carry back 

 to their bivouac all kinds of arthropod animals, especially their larvae 

 and pupae, to feed the busy colony. Accompanying each army ant 

 raid are five or six species of antbirds which do not eat the ants but 

 catch the insects that are flushed by their advancing columns. Dr. 

 Alexander Wetmore, noted ornithologist and former Secretary of 

 the Smithsonian Institution, told me that when he wanted to find 

 certain species of birds he simply followed a column of army ants 

 to its advancing front and almost certainty the birds would be there. 



In the forest practically all the mammals are adapted by structure 

 and behavior to living in the trees or on the ground, with a number 

 that spend considerable time in both. Of the tree-dwelling mammals 

 certainly none is more spectacular than the capuchin monkey (pi. 1, 

 fig. 2) which is found all over the island in troops of 15 to 25 indi- 

 viduals. These troops may be strung out a hundred yards or more 

 through the treetops. It is not unusual to see one of these active 

 little monkeys jump and fall 20 to 40 feet into a lower tree. Never 

 did we see one miss its landing. One evening we watched at close 

 range a troop advancing along the margin of the lake. One old 

 male interested himself in making the large iguanas that rest on 

 branches over the water jump down into the lake. This monkey 

 broke off every dead branch that it could find and threw it into the 

 water. Wliether the capuchin was clearing a new monkey trail of 

 reptiles and dangerous limbs or whether it just liked to see and hear 

 things splash in the water is hard to say, but I am inclined to believe 

 the latter. 



Another curious creature that is almost entirely arboreal is the 

 three-toed sloth (pi. 2, fig. 1). This sloth appears to eat only the 

 leaves of the Cecropia tree and is therefore practically never seen 

 in temperate-zone zoos. One day in the deepest forest I heard a loud 

 squealing and growling in the canopy almost overhead. While I 

 was tryin^to locate the cause of the disturbance two male sloths came 



