ISSN 1067-4136, Russian Journal of Ecology, 2008, Vol. 39, No. 2, pp. 130–135. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © S.A. Shilova, 2008, published in Ekologiya, 2008, No. 2, pp. 141–146.
In the Chernye Zemli (Black Lands) region of the
southern Kalmyk Republic, the midday gerbil (
) and tamarisk gerbil (
) are common species (Popov et al., 1995; Shilova,
1995; etc.), but their ratio and degree of prevalence in
different habitats have changed markedly in the past
decade (Shilova et al., 2000; etc.).
The main purpose of this study was to reveal spe-
ciﬁc features of the spatial distribution and relation-
ships of these two rodent species in the course of long-
term transformations of plant communities in pastures
of the Kalmyk Republic.
The authors of studies on the evolution of closely
related sympatric animal species traditionally devote
much attention to mechanisms reducing competition
between them (MacArthur, 1972; etc.). In sympatric
species of rodents (as well as of other animal groups),
such mechanisms may include the use of different hab-
itats, differences in distribution over microsites within
the same biotopes, and differences in the spatial struc-
ture of colonies and daily activity pattern. Correspond-
ingly, it was proposed that the above parameters of
cohabitant midday and tamarisk gerbils do not coin-
cide. If so, this may be regarded as a mechanism for
alleviating competition between closely related species
sharing the same habitats.
This paper summarizes the data obtained by the
author and specialists of the expedition to the Kalmyk
Republic organized by the Severtsov Institute of Ecol-
ogy and Evolution, Russian Academy of Sciences.
The main stages of this research were performed by
D.Yu. Aleksandrov, A.V. Chabovskii, S.I. Isaev,
V.V. Neronov, and L.E. Savinetskaya (Chabovskii and
Aleksandrov, 1996; Aleksandrov, 1998; Isaev and
Shilova, 2000; Shilova et al., 2000).
STUDY REGION, MATERIAL, AND METHODS
The material was collected near the village of
Achinery, in the Chernye Zemli region of the southern
Kalmyk Republic, from 1993 to 2005. Throughout this
period, rodents were trapped every year, in spring and
autumn, in permanent key plots established in the main
types of plant associations. Geobotanical descriptions
of the plots were made by V.V. Neronov. Censuses of
gerbils were taken by a standard trap-line method. Spe-
ciﬁc features of their distribution over microsites were
studied along a 1-km transect with inspection points
located at 10-m intervals, which traversed an area with
a diverse soil and plant cover (Neronov and Aleksan-
drov, 2004). The distribution of individual home
ranges, settling, and movements of gerbils were studied
by means of individual marking in ﬁve 1-ha key plots.
To study the daily activity of gerbils, live traps set in
four key plots located in different biotopes, with differ-
ent ratios of the species studied, were checked simulta-
neously every two hours, on a 24-h basis.
Interspecific Relationships of the Midday Gerbil
Pall., 1773) and Tamarisk Gerbil
Pall., 1773) in Pasture Ecosystems
of the Kalmyk Republic
S. A. Shilova
Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences,
Leninskii pr. 33, Moscow, 119071 Russia
Received November 8, 2008
—Studies performed in the southern Kalmyk Republic from 1993 to 2005 have shown that the midday
and tamarisk gerbils are similar in their biotopic distribution and that their preferences for certain habitats
depend on speciﬁc features of feeding. Individual home ranges of both species overlap, and the patterns of their
daily activity are synchronous. These facts suggest that there is no interference competition between the midday
and tamarisk gerbils in pastures of the southern Kalmyk Republic.
: midday gerbil, tamarisk gerbil, biotopes, daily activity, interspeciﬁc competition.