Comparative swimming behaviour in four didelphid marsupials

Depending on a mammal's swimming capabilities, water bodies might represent physical barriers or pathways. To evaluate the swimming capabilities of terrestrial didelphid marsupials, we investigated the aquatic locomotion of Didelphis aurita, Metachirus myosurus, Philander quica and Marmosa paraguayana. Individuals were filmed while swimming in an aquarium (1.5 x 0.2 x 0.3 m). All four species presented homolateral quadrupedal swimming gait. The swimming behavior observed was like that presented by the terrestrial species, Didelphis virginiana, and Lutreolina crassicaudata, which is considered semi-aquatic by some authors. The position of the back of Me. myosurus, P. quica and Ma. paraguayana is equivalent to the semi-aquatic Chironectes minimus, with dorsoventral undulation of the tail observed in Me. myosurus like what is observed in C. minimus. Me. myosurus and Ma. paraguayana likely present the best swimming capabilities amongst the studied species.