Habitat selection drives dietary specialisation inSorex minutus

Abstract

19 To meet their demand for food, Eurasian pygmy shrews (Sorex minutus) require large 20 territories, normally in fields, woodlands, and meadows. Their high metabolism and food 21 requirement often leads to high mortality during winter. However, evidence of shrews in 22 the roof voids of residential buildings has recently been observed, contrary to ecological 23 expectations. Here, five faecal samples collected from different locations were studied by 24 metagenomic analysis to gain information about the shrew's diets and environments. Two 25 of the samples were collected from novel indoor locations, while the other three were from 26 outdoors in 'traditional' habitats. Distinct differences were observed between the diets of 27 the two populations, suggesting a commensal niche expansion has occurred in S. minutus. 28 We found that S. minutus exploit man-made spaces for foraging, potentially at the cost of a 29 greater parasite burden. 30 31 Introduction 32 Five species of shrew are known to live in the British isles; the common shrew (Sorex 33 araneus), the Eurasian pygmy shrew (Sorex minutus), the water shrew (Neomys fodiens), the 34 lesser white-toothed shrew (Crocidura suaveolens) and the more recently discovered 35 greater white-toothed shrew (Crocidura russula) which was found in Ireland in 2007 [1, 2]. 36 Here we focus on the Eurasian pygmy shrew (S. minutus), which is the smallest British 37 mammal, measuring approximately 8cm from nose to tail and weighing between 2-5g [3]. 38 Despite their small size, shrews have a very high basal metabolic rate [4-6]. However, other 39 factors involving energy usage -such as thermal conductance and body temperature -3 40 which are also dependent on body mass [7] have been shown to be as expected given the 41 mass of an average shrew [6]. 42 43 This high basal metabolism rate requires huge dietary input, with Sorex species having to 44 eat the equivalent of their body mass every day [8]. Shrews, like the rest of the order 45 Eulipotyphla, are insectivores. They are opportunistic foragers and have been recorded to 46 eat a plethora of invertebrates including Isopoda, Chilopoda, Lumbricidae, Diptera, 47 Hymenoptera, Araneae, Mollusca, and more [3, 9]. The constant demand for energy means 48 that shrews have adopted a polyphasic circadian rhythm, with around ten active periods per 49 day separated by short rests [10, 11]. Activity periods occur during night and day to allow 50 maximum food intake and foraging time. The rest periods rarely, if ever, exceed two hours 51 to prevent starvation [12]. 52 53 Both the common and the pygmy shrew have large, well defended territories [13]. Although 54 the common shrew (S. araneus) is larger than the pygmy shrew (S. minutus), their territories 55 are on average smaller. Mean territory sizes have been reported as 1,058 m 2 for S. araneus 56 and 2,146 m 2 for S. minutus [14]. Whilst there are slight differences in habitat preferences 57 between different shrew species in the UK, in general they all require plant cover (provided 58 by sm...

Primer biases in the molecular assessment of diet in multiple insectivorous mammals

“…In addition, the rate of shrew samples filtered out due to low read counts was much higher than with Gillet. It was evident from this study (and previous studies; Ware et al 2020) that shrews also rely on other terrestrial invertebrate orders such as Gastropoda, Isopoda and Haplotaxida (Fig. 2B).…”

“…Pygmy shrews have a diet consisting of 12 identified orders from multiple hard-part dietary analyses, with Araneae, Coleoptera and Opiliones highly represented across different parts of the species' range (Meharg et al 1990;Churchfield & Rychlik 2006). A recent shotgun metagenomics study (not to be confused with the metabarcoding approach used here) on five individuals also identified the importance of Lepidoptera and Acari (Ware et al 2020). Detailed studies of the greater whitetoothed shrew's diet are limited, but Lepidoptera larvae, Araneae and Isopoda are important components of the species' diet in Europe (Bever 1983).…”

Shrews Under-Represented in Fruit Farms and Homesteads

“…These prey groups should be affected in orchards, but are unlikely to be affected in commensal habitats. Recent observations of S. minutus in commensal habitats (roof cavities) have been attributed to possible avoidance of harsher climates, resulting in a change in diet [ 86 ]. In our study, S. araneus and S. minutus did not differ in stable isotope values between commensal and agro-habitats (see Figure 2 ).…”