J. Biosci·, Vol· 18, Number 1, March 1993, pp 149-153·© Printed in India·
Effect of abiotic factors on the burrow density of some sympatric
field murids
PARMESH KUMAR and S C PASAHAN
Department of Zoology, Chaudhury Charan Singh Haryana Agricultural University, Hisar
125 004, India
MS received 26 February 1992; revised 1 August 1992
Abstract. The burrow density of sympatric murids in relation to various abiotic factors
viz· maximum and minimum atmospheric temperatures, relative humidity, soil temperature
and soil moisture was studied in the agro-ecosystem of village Kakrod-Jind (Haryana)
Analysis of monthly recorded data on burrow density revealed a biomodal pattern i. e. a
peak each during the months of September and March· Of these abiotic factors, soil
moisture revealed significant positive correlation with the burrow density whereas relative
humidity exhibited invariably the least interaction· However, path co-efficient analysis
depicted the direct effects of soil temperature and soil moisture and indirect effect of
maximum and minimum atmospheric temperature through soil temperature on the burrow
density· The use of path co-efficient analysis in such studies has been suggested·
Keywords. Abiotic factors; temperature; relative humidity soil moisture; burrow density;
murids·
1
Introduction
Murids (class; Mammalia; order: Rodentia; family: Muridae), exemplified by mice,
rats, hamsters etc. are among the most ancient and most successful mammals
(Young 1962). Many of these live in underground burrows that they construct. The
density of their burrows varies enormously between habitats and between seasons.
Some studies have been made on burrow densities of field murids in relation to
some abiotic factors in northern India (Ubi 1975; Malhi and Sheikhar 1984).
However, all these studies have considered only one factor at a time. The
conclusion derived from such studies may therefore be misleading. This is because
abiotic factors interact with each other in several complex ways to influence a
biological process. In the present study, data on the burrow density of sympatric
field murids and associated abiotic factors have been analysed using simple
correlation and path co-efficient analysis and a comparison of the two methods has
been made to assertain the causal factor(s).
2
Materials and methods
The study was carried out in the field of village Kakrod-Jind (Haryana). Monthly
recordings of live burrows in an area of 1·35 ha were made from May, 1989 to
April, 1990. Since most of rodents being nocturnal, the burrows were plugged with
the soil late in the evening and freshly opened burrows were counted early in the
morning to estimate the number of live burrows. Monthly recordings of the
atmospheric temperature and relative humidity were made one meter above the soil
149
150
Parmesh Kumar and S C Pasahan
surface by dry and wet bulb thermometer whereas soil temperature was measured
by inserting the soil thermometer at a depth of 15 cm inside the soil. Soil moisture
was recorded with the help of soil moisture meter. The data was analysed for
simple correlation matrix following Snedecor and Cochran (1967).
3.
Results
We found four different murid species viz. Rattus meltada, Tatera indica, Bandicota
hengalensis and Mus booduga co-existing in the experimental area. Analysis of
monthly recordings of the average number of burrows in the study area revealed
that burrow density fluctuated in a wide range from about 134 in September to
about 20 in November (figure 1). There was no clear-cut pattern of dependance of
borrow density with temperature or humidity. However, soil moisture seems to covary with the pattern of burrow density all through the year (figure 1). This is
further supported by the fact that the maximum percentage of soil moisture (35·5)
obtained during the month of September coincided with the peak burrow density
(133·5) recorded during that month.
Figure 1. Relationship between burrow density and abiotic factor.
Correlationanalysis also shows that soil moisture is the only abiotic factor
correlated significantly with the number of borrows (P ≤ 0·01) while correlation with
all other factors are non-significant (P≥0·05) (table 1).
The correlation matrix, however, also shows that some of the abiotic factors
Burrow density of field murids
Table 1. Correlation matrix showing relationship between burrow density and abiotic factors.
*P ≤ 0.05; **P ≤ 0.01.
Table 2. Path co-efficient analysis showing relationship between burrow density and
abiotic factors.
151
152
Parmesh Kumar and S C Pasahan
interacted mutually amongst themselves (table 1). This, therefore, makes it necessary
that the data be further analysed by path co-efficient analysis following the method
suggested by Wright (1921), Dewey and Lu (1959) and Sihag and Abrol (1986). Such
an analysis revealed that both soil moisture and soil temperature influenced the
burrow density, as both these factors acted directly on the number of burrows. Here
direct effect of soil moisture was very pronounced (P = 0·7318) and that of soil
temperature was appreciable (P = 0·3325) (table 2). The direct effect of all other
factors was, however, negligible. Maximum and minimum atmospheric temperature
had no direct effect but their indirect effect through the soil temperature was
considerable (P r = 0·3092 and 0·3198 respectively). The relative humidity on the
other hand, had no direct or indirect effect on the number of burrows.
4. Discussion
During the period of unfavourable conditions rodents stay inside their burrows
which provide them a comfortable and homogenous micro-climate, the soil
moisture playing an important role in controlling it (Prakash 1960, 1971). Pasahan
and Sabhlok (1987) reported emmigration of field rodents as the consequence of
decrease in soil moisture. Contrarily, with better irrigation facilities Garg and
Chandna (1982) observed relatively higher population density of T. indica in the
field. The soil moisture also has a profound effect on the reproductive rate and
population density of murids. Greaves et al (1975) have recorded a higher
pregnancy rate in R. meltada, Nesokia indica and B. bengalensis during the months
of September and October when more soil moisture was available in the fields. The
present investigations have also revealed that soil moisture has a direct correlation
with burrow density of murids. A maximum of 35·5% soil moisture was recorded in
the month of September, which coincided with the highest burrow density
encountered during that period.
Acknowledgement
The authors are highly thankful to Dr R C Sihag, for going through the manuscript
and providing many helpful and constructive suggestions.
References
Dewey D R and Lu Κ Η 1959 A correlation and path co-efficient analysis of components of crested
wheat grass seed production; Agron. J. 51 515–518
Garg S Κ and Chandna S S 1982 A note on the population of gerbils in irrigated and unirrigated fields;
Indian J. Ecol 9 153–155
Greaves J H, Fulk G W and Khan A 1975 A preliminary investigations of the Rice-Rat problem in lower
Sind; All India Rodent Seminar, Ahmedabad, pp 24–28
Malhi C S and Sheikhar C 1984 Burrow intensity fluctuations of rodents in barley crop at Srinagar
(Garhwal); Indian J. Ecol. 11 321–322
Pasahan S C and Sabhlok V Ρ 1987 Effect of removal of wild vegetation on migration of field rodents;
Haryana Agric. J. Res. 27 12–13
Parkash I 1960 Breeding of mammals in Rajasthan desert; India J. Mammal 41 386–389
Prakash I 1971 Breeding season and litter size of Indian desert rodents; Z. Angew, Zool. 58 441–454
Burrow density of field murids
153
Sihag R C and Abrol D Ρ 1986 Correlation and path-co-efficient analysis of environmental factors
influencing flight activity of Apis florea F.; J. Apic Res. 25 202–208
Snedecor G W and Cochran W G 1967 Statistical methods (New Delhi: Oxford and IBH Publishing Co)
pp 160–193
Ubi Β S 1975 Ecological and biological studies on soft furred field rat Millaradia meltada (Gray), M. Sc.
thesis, Punjab Agricultural University, Ludhiana
Young J Ζ 1962 The life of vertebrates (Oxford: Clarendon Press)
Wright S 1921 Correlation and causation; J. Agric. Res. 20 557–585