ISSN 1067-4136, Russian Journal of Ecology, 2016, Vol. 47, No. 3, pp. 315–319. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © A.M. Makarov, E.V. Ivanter, 2016, published in Ekologiya, 2016, No. 3, pp. 236–240.
Dimensional Characteristics of Prey and Their Role
in the Diet of Shrews (Sorex L.)
A. M. Makarov and E. V. Ivanter
Petrozavodsk State University, pr. Lenina 33, Petrozavodsk, 185910 Russia
e-mail: firstname.lastname@example.org, email@example.com
Received November 22, 2014
Keywords: feeding selectivity, trophic niches, division of resources, harvestmen, coleopterans, shrews
Harmonious coexistence within the same territory
of various shrew species having similar body sizes sug-
gests that they differ in ecological characteristics. Dif-
ferences in the biotopic distribution of coexisting spe-
cies of the genus Sorex have been considered in many
publications, but their trophic niches and mechanisms
for division of food resources are still unclear.
Differences in the size of the foraging apparatus
itself are too small to cause any visible divergence in
food supply between different various species. It has
been shown (Zaitsev, 2005) that recent Soricidae are
capable of hunting large (relative to their body size)
and active prey owing to the specific way of chewing.
Therefore, the prey size is rather restricted by the gen-
eral size of a hunting animal than the size of its forag-
ing apparatus. The suggestion that every shrew species
has the upper size limit in prey selection, which is
determined by the metabolic costs and physical abili-
ties, is justified (Chernyshev and Demin, 1992). As
known, small-sized shrews (Sorex minutus, S. miutissi-
mus) are incapable of coping with large invertebrates
(hornworms, large ground beetles, etc.) normally con-
sumed by common (S. araneus) and water shrews
(Yudin, 1962; Sergeev, 1973). However, the aforemen-
tioned large invertebrates constitute an insignificant
amount in the diet of insect eaters, and their main sta-
ple food objects overlap almost completely (Yudin,
1962; Ivanter and Makarov, 2001). Studying the food
supply of wild shrews and its influence on their diet
showed, on the one hand, a clear correlation between
the amount of consumed invertebrates in the stomachs
and their number in soil samples (Churchfield, 1982)
and reveled, on the other hand, that there are prefer-
ences for particular prey size characteristics (partially
overlapping) among the coexisting species S. araneus
and S. minutus (Pernetta, 1976).
Keeping these shrews in captivity provided data
that S. araneus prefers larger food objects in the range
of its potential preys. Its feeding selectivity depends on
the ratio of abundance of different prey size groups. If
other animals occur in the nearby, the frequency with
which small objects are consumed increases (Barnard
and Brown, 1981). However, when the animals are
kept in captivity, it is impossible to consider reliably
such factors as food availability and competition,
which significantly alter feeding selectivity.
In this paper, we made an attempt to reveal, based
on analysis of field materials, whether partial prey size
selectivity in the diet of shrews can significantly influ-
ence the division of resources among coexisting spe-
The materials were collected in 1984 to 2011 in
Karelia (Ladoga Field Station, expeditions to different
regions of the republic). The stomach contents of differ-
ent shrew species were studied: S. araneus (1453 ind.),
S. minutus (315 ind.), Laxmann’s shrew (S. caecutiens)
(140 ind.), even-toothed shrew (S. isodon) (31 ind.),
and Eurasian least shrew (S. minutissumus) (8 ind.).
All shrews were captured by standard methods.
Feeding selectivity of shrews was investigated by
two methods based on the study of their natural diet.
Harvestmen and coleopterans were analyzed.
In five biotopes (bilberry pine forest, oxalis spruce
forest, deciduous forest, alder forest, and overgrowing
cutover area), the following five harvestman species
were recorded: Mitopus morio (Fabr.), Lophopilio palpi-
nalis (Herbst), Lacinius ephippiatus (C.L.K.), Oligol-
ophus tridens (C.L.K.), Nemastoma lugubre (O.F.M.).
The last species is uncommon in the diet of shrews and
therefore was excluded from further consideration.
Other four species were almost inseparable in the
stomach contents and are considered together.
Harvestmen are a convenient object for studying
prey size selectivity in the diet of shrews for several rea-
sons: these invertebrates are highly abundant; all four
species under study are similar ecologically
(Chevrizov, 1981; Adams, 1984); during the snow-free
period, the abundance and body sizes of harvestmen
change significantly; shrews often consume these
invertebrates, whose residues are then reliably identi-
fied in their stomachs. Since the tropchic relations of