The hard task of a short-tailed mouse opossum (Monodelphis) to prey a harvestman (Arachnida: Opiliones)

ABSTRACT Despite the great diversity of small insectivorous mammals and the use of scent gland secretions as a defense mechanism by harvestmen, there is no observation about the effectiveness of scent glands against predators such as small mammals. We report a remarkable harvestman defense mechanism against a small-mammal attack. When a harvestman and a mouse opossum confronted each other inside a cage, the harvestman knocked out the mouse opossum two sequential times before it could attack the harvestman. Although it is a unique observation and there is no information about its frequency in nature, this report stimulates the study of agonistic behavior between small, cryptic species, which are difficult to observe in the field.