12. Jahrestagung der Deutschen Gesellschaft für Tropenökologie - gtö. Ulm, 17 - 19.02.1999: Poster P-1.8


Damage to Macaranga ant-plants by a myrmecophagous squirrel (Callosciurus notatus, Rodentia, Sciuridae) in West Malaysia

Anja Leo1, Walter Federle2, Ulrich Maschwitz3
1 Abteilung Ökologie und Morphologie der Tiere, Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm
2 Zoologie II, Biozentrum, Am Hubland, D-97074 Würzburg, Germany
3 Zoologisches Institut, J.W. Goethe Universität, Siesmayerstr.70, D-60054 Frankfurt, Germany

Many tropical ant-plants ("myrmecophytes") are well protected against herbivory or climber infestation by the help of their associated ants. As a rule, strong herbivory damage or vine overgrowth in these plants is found only when their ant partners are absent.

In the course of our studies on Macaranga ant-plants in SE Asia, however, we have frequently observed conspicuous stem damages which occurred only on ant-inhabited trees. We found out that they were not caused by herbivores, but by ant-eating squirrels. The major predator is most probably the wide-spread Callosciurus notatus Boddaert. The squirrels tear open the Macaranga twigs and destroy the myrmecodomatia in order to prey on ants and/or brood, leaving characteristic tooth tracks. As a result, twigs often break off and young plants can even be killed. In some habitats, up to 100 % of all Macaranga ant-trees showed tracks of recent squirrel attacks. The frequency of squirrel tracks strongly varied between different localities.

In cage experiments with trapped Callosciurus notatus squirrels we could show that the twig-opening behaviour is not innate, but acquired by learning. Squirrels trapped at sites completely free of any ant-plants were "naive" and not capable of opening the offered Macaranga twigs. Since squirrels exclusively damage plants colonized by ants, these "ant-eaters" (ants only representing part of their diet) apparently reduce the mutual benefit of several SE Asian ant-plant associations.