The “all-purpose” trophic strategy of Dromiciops
The common name “monito del monte” refers to the arboreal habits of
this marsupial, which includes opposable thumbs and a prehensile tail,
resembling a small primate. They move relatively long distances (home
range: 1.6 ± 0.6 ha) (Fontúrbel et al., 2012), across the canopy,
reaching 30 meters of height (Godoy-Güinao et al., 2018), and speeds of
1 m/s (3.7 km/h, see Mejías et al., 2021), which for a 20–30 g mammal
is extremely fast (e.g., Djawdan & Garland, 1988). Their agility in
forest canopies permits these animals to forage efficiently on a variety
of food items, for which qualitative descriptions exist, based on faecal
analysis and laboratory preference trials (Amico, Rodríguez-Cabal, &
Aizen, 2009; Celis-Diez et al., 2012; Cortés, Franco, Sabat, Quijano, &
Nespolo, 2011; di Virgilio et al., 2014; Meserve et al., 1988; Quijano,
2008). These studies have shown that D. gliroides does not appear
to be selective (contrarily to other mammals, which select food items
with specific nutrient composition, see Torres-Contreras & Bozinovic,
1997; Woods, 2009), but rather opportunistic (i.e., dietary composition
follows environmental availability, see Bozinovic, Muñoz, Naya, &
Cruz-Neto, 2007; Cortés et al., 2011; Quijano, 2008). However,Dromiciops cannot fulfil its nutritional requirements only from
fruits or insects. Contrarily, it needs a mixed diet of fruits and
insects to maintain a healthy body condition and a proper energy balance
(Cortés et al., 2011). It is well established that differences in the
digestive physiology of vertebrates reflect the historic levels of
specific substrates of the natural diets, linking digestive enzyme
activity, dietary flexibility, and digestive plasticity in an
evolutionary context (Ramirez-Otarola, Narvaez, & Sabat, 2011; Sabat,
Lagos, & Bozinovic, 1999; Sabat, Novoa, Bozinovic, & del Rio, 1998).
Therefore, the digestive physiology of D. gliroides supports the
hypothesis that digestive capabilities are a necessary—but not an
essential—component for explaining dietary selection (Bozinovic &
Martínez del Río, 1996; Cortés et al., 2011; Silva, Jaksic, &
Bozinovic, 2004; Veloso & Bozinovic, 2000).
Fruit availability represents a strong driver of Dromiciopsdietary habits. They select individual fruits according to their size
and colour, exerting important selective forces on plant populations
(Fontúrbel & Medel, 2017), performing long foraging trips to disturbed
forest stands to consume fleshy fruits (Amico, Rodríguez-Cabal, &
Aizen, 2011; di Virgilio et al., 2014; Mora & Soto-Gamboa, 2011;
Salazar & Fontúrbel, 2016). In fact, Dromiciops consumes fruits
from at least 16 species of shrubs, trees, vines, and particularly from
the hemiparasite mistletoe Tristerix corymbosus (see Table 1 in
Amico et al., 2009). Then, considering the assorted nutrient content onDromiciops ’ diet, an interesting set of questions arises, such as
how these requirements vary among individuals at different ontogenetic
stages (Maldonado et al., 2016), or if they exhibit ontogenetic trophic
niche shifts as a logic outcome (Araujo, Bolnick, & Layman, 2011;
Schoener, 1971). Furthermore, considering that male and female
marsupials invest energy differently during the reproductive period,
ecological sexual dimorphism in diet selection could be expected (Araujo
et al., 2011; Schoener, 1971). This is an interesting avenue that can be
explored, for instance, using the most recent technologies in stable
isotope analysis (Maldonado, Bozinovic, Newsome, & Sabat, 2017).