Conservation, Threats, and Future Trends
As an arboreal marsupial, a key issue for Dromiciops persistence
is its dependence on forest habitats with certain structural features
(Fontúrbel, Candia, Salazar, et al., 2014). Even though the IUCN updated
its threat category from Vulnerable to Near Threatened in 2011, the main
problem persists: habitat loss. The southern South America temperate
rainforests are rapidly being cleared due to land-use change (Echeverría
et al., 2006; 2007). Therefore, suitable habitat for D. gliroidesis not only reduced but also becoming increasingly fragmented and
degraded. Habitat fragmentation has a negative effect onDromiciops abundance, causing local extinction in small fragments
(Rodríguez-Cabal, Aizen, & Novaro, 2007), and collapsing seed dispersal
services (Amico & Aizen, 2000; Amico et al., 2011). Fragmentation
threatens this marsupial as it is unable to disperse through open
habitats (e.g., pastureland), remaining confined to the extant forest
fragments (Fontúrbel, Silva-Rodríguez, Cárdenas, & Jiménez, 2010).
Although some authors have recorded D. gliroides in exotic
plantations (Fontúrbel, Candia, & Botto-Mahan, 2014; Uribe et al.,
2017), a fragment of a native forest was always found in the vicinity,
where they maintain their nesting sites (Salazar & Fontúrbel, 2016). As
a strict arboreal mammal, D. gliroides require a dense forest
with a complex three-dimensional architecture covering the whole
vertical matrix. In fact, the discovery of Dromiciops as high as
30 m above ground in the canopy using camera traps were expected but
difficult to document precisely (Godoy-Güinao et al., 2018; Tejo &
Fontúrbel, 2019). Forest requirements, together with frugivorous habits,
configure a strong dependence on a very special kind of ecosystem
characterised by the combined presence of the native bamboo
(Chusquea spp.) and Nothofagus spp. and Myrtaceae plants
(Rodríguez-Cabal & Branch, 2011), influencing the particularities ofDromiciops nest. Nests are considered part of an organism’s
‘extended phenotype’ (Rubalcaba, Polo, Maia, Rubenstein, & Veiga,
2016), imprinted by the same combination of environmental and genetic
factors of standard phenotypic variation. In the case of Microbiotheria,
several lines of evidence suggest that the nest is fundamental for their
survival (Franco, Contreras, & Nespolo, 2013; Hershkovitz, 1999;
Honorato et al., 2016). Dromiciops nests are built as an oval
cavity covered by a scaffold of tightly interwoven bamboo leaves
combined with mosses and Hymenophyllum ferns (Celis-Diez et al.,
2012). This structure is impermeable and well insulated. Some authors
have also attributed antimicrobial properties to it (Honorato et al.,
2016), as its thick structure and the acid pH of the Chusqueaspp. leaves may protect from predators and have a biocidal effect
against parasites and pathogens.
Since D. gliroides distribution and abundance are influenced by
several factors (particularly bamboo and mistletoe abundance;
Rodríguez-Cabal & Branch, 2011), transformed habitats can give valuable
insights on D. gliroides persistence probabilities in a changing
world. A telemetry-based study (Salazar & Fontúrbel, 2016) showed thatD. gliroides movement behaviour was similar between native and
transformed habitats (and consistent with other locations reported by
Fontúrbel et al., 2012). However, its occurrence in transformed habitats
was mainly determined by neighbouring native remnants in the landscape
where D. gliroides nests. Animals loaf in these native patches
during the day, but perform foraging trips to abandoned plantations
during the night (Salazar & Fontúrbel, 2016), attracted by many
shade-intolerant plant species that provide abundant fruits, such asAristotelia chilensis , Rhaphithamnus spinosus , orUgni molinae (Fontúrbel et al., 2017a).
Another major threat to this species is climate change. Given its
hibernating habit, even a slight increase in winter temperatures can
drastically affect them. In this case, heterothermy is Dromiciopsnormal condition, and it needs to hibernate during the winter to survive
with the energy reserved collected during the summer (Nespolo, Mejías,
et al., 2021). Thus, climate change emerges as a critical threat to this
species as warmer temperatures necessitate extra energy expenditure,
resulting in a lower survival probability (Nespolo, Fontúrbel, et al.,
2021). Furthermore, severe and prolonged droughts are a consequence of
climate change and can cause moisture stress in plants. Such moisture
stress causes significant reductions in flower and fruit production
(Fontúrbel, Lara, Lobos, & Little, 2018), indirectly reducingDromiciops energy reserves. Altogether with the destruction of
its habitats, climate change may relegate this species and, with it, the
entire order to the fossil record if no actions are taken in the short
term. Thus, Dromiciops local extinctions may have cascade effects
in the community as a result of the loss of the seed dispersal services
that this marsupial performs.