The feeding and ranging behaviour of Galapagos giant tortoises (Geochehne elephantopus) The Cambridge and London University Galapagos Expeditions, 1972 and 1973

Abstract

Field observations on the behaviour of adult Galapagos giant tortoises (Geochehne elephantopus) on the islands of Santa Cruz (Indefatigable) and Pinzon (Duncan) were made by the 1972 Expedition, and on Santa Cruz by the 1973 Expedition. The animals (in all 14 on Santa Cruz and three on Pinzon) were observed continuously throughout the day for periods of 3–14 days so that their main non‐reproductive activities (feeding and walking) could be quantitatively recorded. The period of potential activity was between about 08.00 hrs and 16.00–18.00 hrs, but the pattern of behaviour was extremely variable, both in a given individual and between one individual and another; it seemed little influenced by the relatively slight fluctuations of temperature and climate which occurred during the period of study (July‐September) on Santa Cruz. The tortoises on Pinzon, a much more arid island, were less active, and one showed a strongly bimodal activity pattern with a resting period during the middle of the day. The animals studied in 1972 showed a strong disposition to return after several days to the same sleeping place, but this homing tendency was not observed in 1973. This discrepancy can perhaps be attributed to the fact that the two expeditions worked in different areas under different weather conditions. Observations on the plants eaten, on the association between tortoises and certain birds, and on some other aspects of tortoise behaviour such as walking speed and responses to sounds are also described.

Study of the carapace shape and growth in two Galápagos tortoise lineages

“…Tortoises from Cerro Fatal appeared to have a higher and more compressed carapace shape and wider vertebral scutes compared with tortoises from La Reserva, which instead have a longer carapace, more expanded on the sides, with higher sulcus of the marginal the pleural scutes, and a relatively higher first vertebral scute. Our results support an early observation (Rodhouse et al,1975) done on tortoises from La Reserva, for which some animals although having a characteristic general domed shell form, also showed a slight upward opening on the front of the carapace.…”

Self-righting potential and the evolution of shell shape in Galápagos tortoises

“…The higher anterior opening of the shell of saddleback tortoises facilitates raising the neck higher than domed tortoises can, and could therefore have evolved to allow the animals to use this source of food 17–19 . However, this seems unlikely, as saddleback tortoises currently only seldom feed on Opuntia tree 25,34 . However, this may have been a much more important food resource for saddleback during their evolution.…”

“…Field observations indicate that saddlebacks feed primarily on Opuntia when other vegetation is scarce ( e . g ., years of drought, for example during La Niña or especially dry seasons 35 ), while most of time, as in many other tortoises, they eat any available plants and fruits 25,34,36 (but see 23 ).…”

Documenting Aggression, Dominance and the Impacts of Visitor Interaction on Galápagos Tortoises (Chelonoidis nigra) in a Zoo Setting

“…Members of the public may also be able to touch tortoises, as well as undertake shell scrubbing or initiating the finch response [4]. The finch response is a natural behaviour in which a tortoise will stretch out its limbs and head to allow birds such as finches or mocking-birds to remove ectoparasites [8,9]. This can be initiated by scratching the neck or legs of the tortoise, resulting in the tortoise performing the same outstretched pose [9].…”