Spool and line studies on the behavioural ecology of rats (Rattus spp) in the Galapagos Islands

The spool-and-line technique has been neglected in the study of the behavioural ecology of mammals. It has advantages over the more widely used method of radio tracking in terms of cost and depth of detail in the data obtained, despite its limitations. A spool and line was used to study habitat use of two species of Rattus on Santa Cruz Island, Galapagos, in areas of sympatry and allopatry. Significantly longer total spool lines were collected from R. rattus than R. norvegicus, and R. rattus also climbed trees significantly more. Significantly longer spool lines were collected from female than male R. rattus, and rats caught in the morning spent significantly more time on the ground than those caught at night. The method of handling and the occasion of capture (first, second, or third) had no significant effect on either the total length of spool line collected or the proportion of time spent on the ground. Arboreality in R. rattus was compared with that in R. norvegicus between areas of sympatry and allopatry, and a significant difference was found between sites in terms of both the total length of spool line collected and the proportion of time spent on the ground. Rattus rattus was least arboreal at site D, an area of allopatry, and most arboreal at site B, where the fewest trees occurred, suggesting that factors other than vegetation structure influence arboreality. The use of spool-and-line devices in the study of behavioural ecology is discussed.