Vol. II, Pt. I] VAN DENBURGH— GALAPAGOS TORTOISES 235 



like in habit, growing usually to a large size, and it is only the 

 young and smaller plants that are within reach of the tortoises. 

 Grass can be secured much easier, and it is perhaps due to this 

 fact that it forms a larger proportion of their food. 



"The tortoises do a great deal of apparently unnecessary 

 traveling; and, though slow, are so persistent in their journeys 

 that they cover several miles a day. Most of the traveling is 

 done early in the morning and late in the afternoon, the hot 

 hours of noon being spent in the shade of some bush, wallow- 

 ing in the damp soil. The wallowing probably cools them, and 

 incidentally relieves them of a few of the numerous wood ticks 

 (Amblyoma pilostim) which infest them at the joints and wher- 

 ever the skin is thin enough to allow them to pierce it. After 

 heavy rains they delight to wallow in the mud. They are very 

 determined travelers, and once started in a certain direction no 

 obstacles can stop them. Not infrequently they ascend very 

 steep, rocky hills. Sometimes their shells are broken, and 

 occasionally they are killed, by rolling down these inclines, but 

 if uninjured after these falls they will make repeated efforts to 

 reascend until crowned by success. They retire early for the 

 night, drawing in their limbs and neck, and after sunset do 

 not move from the place chosen for the night. Darwin, how- 

 ever, states that they travel both day and night when on their 

 periodical visits to the springs. 



"All three of the species we observed make seasonal vertical 

 migrations. Soon after the rainy season they descend the 

 mountains to the grass-covered flats at their bases, to feed and 

 deposit their eggs in the light soil. After the grass has with- 

 ered, they again ascend the mountains to the moist meadows 

 produced by the trade winds at an elevation of 2,000 feet and 

 above. These migrations are most marked in the dry regions, 

 as at Tagus Cove, Albemarle ; but even at Iguana Cove on the 

 same island, where there is an abundance of moisture at lower 

 elevations, a nearly complete migration takes place. On Dun- 

 can Island the tortoises scatter out so in the dry season that 

 their movements can scarcely be called a vertical migration. 

 In their seasonal pilgrimages they follow well-established trails 

 used perhaps for generations. These trails radiate from the 

 higher plateaus as a center and usually follow the floors of 

 the canyons to the flats below. Some of the trails are of 



September 30, 1914. 



