Behavior of Mound-Building Mouse, Mus Spicilegus During Autumn-Winter Period in Captivity

Abstract

Mus spicilegus is an outdoor species from southern-eastern Europe, adapted to agroecosystems. In the beginning of autumn, to spend the winter, mound-building mice build complex mounds. These mounds are built using accumulation of seeds covered with earth. This behavior is unique among mice species. However, there is evidence that at higher temperatures and a larger availability of food in winter, mice can optimize this particular behavior in direction to simpler constructions or even not build them at all. To clarify if mice display building activity under laboratory conditions we studied behavior of M. spicilegus in 5 intraspecific cage groups during autumn-winter period. The observations were carried out in 100 x 100 cm glass cages provided with earth and sawdust as bedding and straw and hay as nesting material. The groups were formed by 3-4 mice captured from a wild population in northern Bulgaria in early September of 2008, where mounds were already built. Mice were grouped according to the mound they belong to. The results showed that mound-building mice display high level of building activity, especially in the first month of their time in the laboratory. In majority of groups mice built domed nests made from straw and hay, where they lived together. Seeds in the cages were covered with earth, as far as that was possible. However, mice in some groups made burrows of simple design. Based on these findings it could be assumed that building behavior of M. spicilegus is genetically determined, but as microtine rodents M. spicilegus can be quite flexible in employing behavior to suit the local environment.

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XI ANNIVERSARY SCIENTIFIC CONFERENCE BIOTECHNOL. & BIOTECHNOL. EQ. 23/2009/SE
120 YEARS OF ACADEMIC EDUCATION IN BIOLOGY SPECIAL EDITION/ON-LINE
45 YEARS FACULTY OF BIOLOGY
180
BEHAVIOR OF MOUND-BUILDING MOUSE, MUS SPICILEGUS DURING
AUTUMN-WINTER PERIOD IN CAPTIVITY
D. Simeonovska-Nikolova, Sh. Mehmed
Department of Ecology and Protection of Nature, Faculty of Biology, Sofia University “St. Kliment Ohridski”, 8 Dragan
Tsankov blvd., 1164 Sofia, Bulgaria
Correspondence to: Daniela Simeonovska-Nikolova
E-mail: mammals@abv.bg
ABSTRACT
Mus spicilegus is an outdoor species from southern-eastern Europe, adapted to agroecosystems. In the beginning of autumn, to
spend the winter, mound-building mice build complex mounds. These mounds are built using accumulation of seeds covered
with earth. This behavior is unique among mice species. However, there is evidence that at higher temperatures and a larger
availability of food in winter, mice can optimize this particular behavior in direction to simpler constructions or even not build
them at all. To clarify if mice display building activity under laboratory conditions we studied behavior of M. spicilegus in 5
intraspecific cage groups during autumn-winter period. The observations were carried out in 100 x 100 cm glass cages
provided with earth and sawdust as bedding and straw and hay as nesting material. The groups were formed by 3-4 mice
captured from a wild population in northern Bulgaria in early September of 2008, where mounds were already built. Mice
were grouped according to the mound they belong to. The results showed that mound-building mice display high level of
building activity, especially in the first month of their time in the laboratory. In majority of groups mice built domed nests
made from straw and hay, where they lived together. Seeds in the cages were covered with earth, as far as that was possible.
However, mice in some groups made burrows of simple design. Based on these findings it could be assumed that building
behavior of M. spicilegus is genetically determined, but as microtine rodents M. spicilegus can be quite flexible in employing
behavior to suit the local environment.
Keywords: building behavior, intraspecific cage groups, Mus
spicilegus, nest design, time budget
Introduction
The mound-building mouse (Mus spicilegus Petényi 1882) is
an outdoor species from south-eastern Europe, adapted to
agroecosystems. In the beginning of autumn, mound-building
mice build complex mounds (2, 9, 10, 15). In order to spend
the winter, these mounds built represent an accumulation of
seeds covered with earth. The mounds serve as food
reservoirs during the winter period, especially for the young,
immature individuals born in the autumn (13). According to
(2), mound building appears to be kin based, and the
evolution of mound building and communal nesting in this
species would then be partly due to kin selection. In spring,
mound-building mice about 6 months old leave the mound
and begin to reproduce (3, 6, 10, 13, 15, 17).
Although M. spicilegus is unique with its ability to
construct complex earthen mounds, data suggests that under
higher temperatures and a larger availability of food in winter
mice can optimize this behavior by building simpler
constructions or even not build them at all. For instance an
interesting field observation has been registered in Greece
where a pair built its nest in the middle of a discarded, 2m
long, plastic piece of irrigation tube (7). This deviation from
the mound-building ethology raised questions about building
activity of M. spicilegus and factors that affect it. In order to
clarify whether mice display building activity under
laboratory conditions, we studied behavior of M. spicilegus in
5 intraspecific cage groups during autumn-winter period. We
hypothesised that the behavior of M. spicilegus individuals
and their building activity reflect their life-history traits.
Materials and methods
The mound-building mice were collected from a wild
population of M. spicilegus in the region of Northern
Bulgaria (43°21’N, 24°15’E). Mice were caught in an
agricultural area at the beginning of September of 2008 using

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live-traps. During the period, mounds in this agroecosystem
were built. The live-traps were distributed around each
mound in order to capture kin-related or familiar mice.
A total of 17 mice were captured. Behavior of mice
captured was tested in 5 intraspecific cage groups – 2 male
and 4 mixed. Each group consisted of 3-4 individuals. Mixed
groups consisted of 2-3 males and 1 female. Mice in each
group belonged to the same mound. The group composition
was based on the demographic structure of the population in
early autumn period of 2008 – males dominated over the
females nearly 2:1. All mice in the groups were juveniles.
The age of each animal was determined on the base of its
body mass and reproductive status (juveniles, < 10 g).
The experiments were carried out in 100 x 100 cm glass
cages. Each cage contained earth and sawdust as bedding, as
well as nesting material – straw and hay. The animals
captured were kept in the laboratory at a temperature of 15°C
± 2°C, humidity (approximately 60%) and natural daylight.
They were fed on a mixed seed diet supplemented with
apples and provided with water.
The study on behavior of M. spicilegus in intraspecific
cage groups was conducted by regular observations for half
an hour 2-3 times a day till the end of February 2009. In
addition during September and November mice in 3 groups
were observed and recorded using 24 h video surveillance in
order to determine time budgeting behavior during the
autumn-winter period. Relative time spent on each behavioral
category was calculated and analyzed. The significance of
differences between behavioral patterns, demonstrated by
mice in September and November were estimated by one
sample χ 2 test at p < 0.05.
The behavioral events demonstrated by M. spicilegus in
the experimental groups are as follow: 1. Individual behavior:
locomotion (activities such as walking, running, or jumping),
self-grooming, digging (the animals perform digging
movements with hind legs), building (the animals move
pieces of straw with their muzzles and gather them in a given
spot in the cage, resting (movements are absent while the
animals are in the nests or they stop moving for a short time),
eating and drinking; 2. Social behavior: agonistic behavior –
offensive behavior (threat, attack, fight, chase, offensive-
upright and sideways postures), defensive behavior
(defensive-upright posture, jumping apart, pushing forepaws
against opponent, running away, crouching, submissive
posture), and amicable behavior (approaching, following,
nose-nose, nose-anal, nose-body, passing above, pushing
under, grooming, clambering on, standing side by side).
Pattern of behaviour and terms used for each pattern were
borrowed from studies on rodents by (1, 5, 12, 15, 16). The
investigation conformed to international requirements for
ethical attitude towards animals (4).
Results and Discussion
High levels of loco-exploratory activity were observed after
the initial introduction of mice to the cages. During the dark
period, since the species is essentially nocturnal, mice were
active and showed high levels of building and digging
activity. This was evident especially in the first weeks of
mound forming (Fig. 1). The animals moved pieces of straw
with their muzzles and gathered them in a given spot in the
cage. (Fig. 2). During the day mice mostly slept (Fig. 3). M.
spicilegus individuals displayed significantly more building
and digging activity in September in comparison to
November (χ 2 = 54.2, p < 0.001 for building activity, χ 2 =
20.1, p < 0.001 for digging activity (Fig. 1). The general
described pattern is similar to other rodent species (8, 18).
Many studies conducted in laboratory and semi-natural
conditions demonstrate that male as well as female M.
spicilegus are aggressive towards unfamiliar individuals (11,
12), but tolerant to familiar individuals (12). In the present
study, conflicts were registered only in one group during the
first week of their forming. In the rest of the groups mainly
amicable behaviors were observed. Therefore, social
interactions of M. spicilegus individuals seem to reflect these
life-history traits.
Results demonstrated that mice in some of the groups built
domed nests made from straw and hay with length 13–26 cm,
width 11–16 cm and height 4–12 cm, where they live together
during the entre autumn-winter period. They looked like small
piles (Fig. 4). The nests were built up by mice until the end of
September and the beginning of October, a period that is consisted
with observations done in the wild (13, 15, 17). Seeds in the cages
were covered with earth, as far as that was possible. However,
mice in other groups made burrows of simple design. Based on
these findings it could be assumed that building behaviour of M.
spicilegus is genetically determined, but as microtine rodents M.
spicilegus can be quite flexibile in employing behavior to suit the
local environment. Such flexibility can account for the fact why
some mice did not build any nest at all.

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Building
0
5
10
15
20
25
30
35
40
2.00-3.00
4.00-5.00
6.00-7.00
8.00-9.00
10.00-11.00
12.00-13.00
14.00-15.00
16.00-17.00
18.00-19.00
20.00-21.00
22.00-23.00
24.00-01.00
Hours
Minutes
September
November
Fig. 1.Building activity of mound-building mice in September and November of 2008.
Fig. 2. Pieces of straw gathered by mice in a given spot in the cage. Fig. 4. A domed nest made from straw and hay.
Resting
0
10
20
30
40
50
60
70
2.00-3.00
4.00-5.00
6.00-7.00
8.00-9.00
10.00-11.00
12.00-13.00
14.00-15.00
16.00-17.00
18.00-19.00
20.00-21.00
22.00-23.00
24.00-01.00
Hours
Minutes
September
November
Fig. 3. Resting periods displayed by mound-building mice in September and November of 2008.

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Acknowledgements
This work was supported by a grant from the Sofia
University “St. Kliment Ohridski”. We thank W. Tong and
K. Dimitrov for their assistance in the capture and
transportation the mice.
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