Confirmation of arboreal habits in Dromiciops gliroides: a key role in Chilean Temperate Rainforests

Dromiciops gliroides is a small marsupial endemic to the South American temperate rainforest; it is considered a living fossil because it is the only living species of the order Microbiotheria, more related to Australian marsupials than those found in South America. Dromiciops gliroides has been considered a scansorial marsupial most frequently found in the understory. Nonetheless, several authors have hypothesized that this species could be arboreal because of its ability to climb through the vegetation. However, all previous studies on D. gliroides have been conducted from the ground, with no documentation of this species’ ability to climb trees, or how high they may reach. Here, we present the first evidence of arboreal habits in D. gliroides, and we analyze its functional importance for the biodiversity of forest canopies. In the Bosque Pehuén Park (39°25′ S, 71°45′ W), in six emergent Nothofagus dombeyi (Nothofagaceae) trees, we installed camera traps, one per tree, between 12 and 21 m aboveground, in the trees’ crowns. Camera traps were active from January to April of 2017, during the Southern Hemisphere's summer and fall. We recorded a total of 2319 photographs, including small mammals, birds, and lizards, in addition to several unidentified species. A total of 230 photographs of D. gliroides were recorded, across all six of the surveyed trees. In a more recent survey (February 2018), we found this species at 26 m, 2 m from the tree's highest point. Dromiciops gliroides is thus a frequent canopy user and could influence canopy biota and ecological processes. Dromiciops gliroides is considered a seed disperser of most vascular epiphytes and vines, and may therefore strongly influence epiphytic dynamics. It is also an active invertebrate predator and as such could significantly decrease tree herbivory. The roles that D. gliroides plays in this ecosystem need more clarification; this living fossil may be more important for this forest ecosystem than previously believed, modulating biodiversity and functions in unexpected, yet relevant ways.