Demographic consequences of selective logging for the arboreal marsupial Dromiciops gliroides in Chiloé Island, Chile

Background/Question/Methods

We assessed the consequences of selective logging for population size and growth of the endemic arboreal marsupial Dromiciops gliroides (Microbiotheria) in temperate rainforest remnants immersed in the rural landscape of northeastern Chiloé Island (42^o S), Chile. This small marsupial hibernates in tree cavities and logging is expected to affect habitat quality. We surveyed marsupial populations in two old growth (OG) and two selectively logged (SL) forests, which were representative of remnant forests in the rural landscape of the Island, where this marsupial occurs. OG forests were characterized by a higher density of larger canopy trees (> 30 cm dbh) and snags, than SL forests, however, the cover of understory native bamboo (Chusquea sp.) was higher in SL than in OG forests. We expected that habitat changes due to the loss of large trees in logged patches should have negative effects on the demography of D. gliroides, especially by reducing winter survival. Individuals were live-trapped for five consecutive years (2005–2010) in a LTER site (Senda Darwin Biological Station), Chiloé Island, during the mating (November) and non-mating (February) seasons. Demographic parameters were modeled using mark-recapture procedures. 

Results/Conclusions

Demographic parameters estimated, such as monthly survival, did not differ between habitat types (logged vs. unlogged forest) or seasons (spring vs. winter), however, varied among years. Annual recruitment differed between seasons each year. Yearly population growth rate of the arboreal marsupial was similar between logged and unlogged forests but showed inter-annual variability and differed among forest fragments regardless of logging. We conclude that small-scale, selective logging by removing individual trees, as a traditional practice, from remnant OG forests in northern Chiloé Island did not translate into negative demographic consequences for this arboreal marsupial, despite important changes in habitat structure. The maintenance or increase of the dense understory bamboo cover may be a key element for the persistence of the marsupial population, by providing nesting materials, protection from predators, and food resources (i.e., arthropods). This result constitutes an important finding towards the conservation of this forest-dependent relict species through responsible forest management practices in anthropogenic rural landscapes.