How far do animals move? Routine movements in a tortoise
ADRIAN HAILEY
Received February 12, 1988
HAILEY, A. 1989. How far do animals move? Routine movements in a tortoise. Can. J. Zool. 67: 208-215.
Although many aspects of the ecology and physiology of animal movement have been well studied, little is known about the distance moved during routine activity. To examine this problem, daily movements of adult tortoises Testudo hermanni were measured by thread trailing. The activity season was about 210 days per year; individual tortoises were active on 95% of days from April to June, but only on 49% of days in the dry months, July-October, probably because of a digestive bottleneck caused by dry food. Daily movements ranged from 1 to over 450m, with a daily mean over a year of 80m in males and 85m in females; there was significant variation between months. Daily movements were 5-10 times less than those of similarly sized mammals. Individuals were active on average for 140 days per year, moving a total of about 12 km. Routine movements occurred within home ranges of 1.8 ha. The intensity of use of the home range was thus 12 km/ 1. 8 ha, equivalent to annual sampling of a strip 1.5-m wide. Food plants were approached over distances of 1-2 m, so that on average all points within the home range were sampled for food once per year; mates were detected over much larger distances. Tortoises used many refuges spread throughout the home range, and rarely returned to the same refuge. Most refuges were insubstantial and gave only concealment and shade: only one-third provided physical protection. This pattern of refuge use is permitted because tortoises have an armoured carapace, the transport of which is estimated to be energetically less expensive than daily return to an environmental refuge.