Characteristics of animal-derived diet in the Chinese mole shrew
The diets of the Chinese mole shrew in our study are similar to the diets of other shrews (such as Sorex and Blarina ) (Churchfield 1982; Churchfield et al. 2012; Churchfield et al. 1999; Churchfield and Sheftel 1994; Churchfield and Rychlik 2006; De Pascual and De Ascencao 2000), which include diverse invertebrates with a preponderance of earthworms (Table 2, Figure 1B, 5 and Supplementary Table 1). The Chinese mole shrew can also be considered as an earthworm-eating shrew. Using molecular technique, we obtained a sufficiently higher taxonomic resolution of food identification, especially earthworms (a total of 12 earthworm species were identified), compared to previous dietary analysis of shrews. Similar to early studies (Churchfield and Rychlik 2006), many of the invertebrates eaten by A. squamipes are typical soil inhabitants (e.g., Oligochaeta and Formicidae), suggesting that this species of shrew is mainly subterranean in its foraging mode. Short tailed shrews are well adapted to a subterranean lifestyle and can push through soil and leaf litterwith their long proboscis and elongated claws (Wu et al. 2011; Churchfield and Rychlik 2006). These special morphological adaptations help to capture earthworms and ants depending on A. squamipessemifossorial foraging behavior (He et al. 2016).
On the other hand, the preys of the Orthoptera, Formicidae, Coleoptera, Dermaptera, Diptera, and Lepidoptera families were occasionally observed during a particular season but only contributed a small amount of prey volume. Unlike the Chinese mole shrew, some other shrew species have been reported to predominantly feed on arthropods, not earthworms. For instance, Diptera (files), Formicidae (ants) and Araneae (spiders) were the most prey species among Southern short-tailed shrew (Blarina carolinensis )(Sylvester et al. 2012). The diet of European water shrew (Neomys fodiens bicolor ) is composed mainly of lumbricids, isopods and dipterans (Churchfield 2009). Isopterans (termites) and formicids were found to be the most frequent food items in the diet of elephant shrews (Elephantulus myurus ) (Churchfield 1987). Lepidoptera larvae are the most common prey for masked shrew (Sorex cinereus ) (Bellocq and Smith 2003; McCay and Storm 1997), followed by Coleoptera (beetles) and Aranea (spiders). The variations in diet compositions between different shrew species also imply that each one chooses what types of prey to feed on, presumably in relation to their morphological adaptations or according to the availability of food resources (Bellocq and Smith 2003; De Pascual and De Ascencao 2000).
Seasonal variations in animal-derived diets in Chinese mole shrew
We also observed decreasing trends in diversity, proportions and FO of invertebrate consumption from spring to winter (Figure 1 and Table 1). One plausible explanation is the fact that seasonality has a strong effect on the density, biomass, and reproductive activity of the earthworm population (Kumar et al. 2018; Monroy et al. 2006). For instance, the maximum density and mating activity of earthworms were achieved in spring (Biradar et al. 2008; Monroy et al. 2006). Furthermore, freezing weather and harsh climate conditions in winter influence the abundance and activity of food resources that can make it challenging for organisms to obtain sufficient amounts. For example, the activity of invertebrates is highly temperature-dependent, and insect flight activity declines dramatically as the ambient temperature drops (Churchfield et al. 2012; Hope et al. 2014). In addition, a previous study showed that although earthworms were present in the soil profile in winter, their numbers and activity were sharply reduced (Khanam et al. 2016). In the case of snow cover and frozen soils, earthworms become dehydrated and hibernate (Churchfield et al. 2012). Randolph (1973) and Rozen (1988) also found that earthworm biomass clearly decreases from summer to winter. Moreover, McCay and Storm (1997) found that earthworms and other arthropods were more abundant in irrigated plots during both spring and autumn, suggesting greater availability of certain foods. Thus, earthworms may not be sufficiently abundant and available especially in winter. These findings strongly supported our results with respect to decreases in the proportions and numbers of earthworms consumed by A. squamipesduring winter (Figure 1B). With their large surface-area-to-volume ratios, short fasting endurance, and high metabolic rates, non-hibernating shrews need adequate food intake for maintaining endothermy and meeting high-energy requirements at low temperatures (Brown et al. 2014; Churchfield et al. 2012; Churchfield et al. 2010). The increased consumption of relatively unpalatable and unprofitable prey, such as Deroceras laeve and Camponotus thadeus , in winter (Table 2 and Supplementary Table 1) suggests that shrews are less preferential in winter than in summer, which is consistent with previous findings (Churchfield et al. 2012). Thus, the Chinese mole shrew selectively shifts its dietary preference throughout the year to adapt to seasonal foods resource availability.