Ecology of the Desert Rodents of the USSR. (Jerboas and Gerbils) *)
by N. P. NAUMOV & V. S. LOBACHEV

[...]

MONGOLIAN GERBIL or CLAWED GERBIL

Meriones unguiculatus Milne-Edwards 1868

Occurrence

It inhabits the sandy steppes of middle, southern and north-eastern Mongolia, avoiding the mountainous regions. In the north, it penetrates the Tuvinian ASSR and the southern part of Tchitinskaya district. During the fourties of this century two isolated populations of this gerbil were found in the lower parts of Orhona and Urda, separated from its main habitat by more than 300 km (BANNIKOV, 1954). In recent times, the gerbil has colonized the intermediate territories (NEKIPELOV, 1959 ; DULAMZEREN, 1970). The animals had reached the northern limits of its range presumably by beeing transported over there (HAMAGANOV, 1954).

In the south, the Mongolian gerbil inhabits the sandy deserts of north and north-eastern China. In the Tuvinian ASSR it lives mainly on the arable lands and deposits in the mountainous wormwood-cereal steppes, and at lower altitudes in the desert steppes and old deposits overgrown with Caragana microphylla (LAVRINENKO & TARASOV, 1967).

It is not found in steppe of mixed grasslands and in rocky and marshy areas in Baikalie. It is found around human settlements and more commonly in wormwood steppes (6 animals per hectare), saline areas (upto 15 animals per hectare) and in fields and pastures (upto 90 animals per hectare). They also inhabit dry sandy steppes, overgrown with Caragana microphylla and white wormwood and can be found in steppes with light loamy soils with a mixed cover of cereal plants and grass species of different types. It occours there in fields of crops such as buckwheat, millet and wheat and is quite numerous on artificial earthen embankments along railway tracks and metalled and unmetalled highways and on the banks of irrigation systems. It digs burrows on rubbish heaps and in earthen buildings (NEKIPELOV, 1962). It avoids virgin soils (LEONTJEV, 1954). In the southern part of Mongolia this gerbil has no particular preference for sandy grounds. It is found to occur there on more compact soil. In the north east it has been found in steppes with cereal plants on sandy hillocks with Caragana cover and in saline patches and in salt-marshes carrying Salsola. They are usually most numerous on rubbish heaps on the outskirts of vegatable gardens (LIPAEV, 1967). There most usual haunts are the areas of cereal-Salsola-Caragana association in the semi-deserts and sand dunes overgrown with Nitraria. They can easily adapt themselves to rocky habitats as well as to relatively humid areas with cover of Iris tenuifolia and Lycium sp. So, from the south to the north these animals increasingly tend to be attracted to light dry soils. In the same direction the degree of sinantropism increases, and it can be seen most vividly in the northern settlements of these animals. In East Mongolia 36 per cent of the rodents found in homesteads are gerbils (KUCHERUK, 1946).

Population density

The number of clawed gerbils in an area vary considerably. Upto 32 burrows (with 760 entrances) per hectare have been recorded in Zabaikalie. The average density is lower at certain times (LEONTJEV, 1954). The data of LAVRINENKO & TARASOV (1967) for the Tuvinian ASSR reporting 70-176 animals per hectare, appear to be too much on the high side. The average number of burrow entrances per hectare was 42 in the Mongolian cereal-Caragana desert, while there are 504 such entrances per hectare in dune areas and 2800 in the culverts along the highways (Observations made in May 1944; BANNIKOV, 1954). In Zabaikalie in similar culverts there were 740-1420 entrances, while 2500 entrances were found on the deposits and only 30 to 32 entrances in virgin soil. The great fluctuations in the number of these openings indicated the instability of the resident population of this gerbil.

Food and Storing Behaviour

The clawed gerbils eat seeds and green parts of many plants. In summer they prefer to eat green parts and in winter seeds and fruits. The composition of plant species, consumed by these animals, is found to be different for different regions. In the agricultural fields in Zabaikalie and Tuva mostly the seeds of crop plants are eaten. In fallowlands their food comprise cereals, wormwoods and plants of Chenopodiaceae, Compositae, Leguminosae and other families. In the food stores inside their burrows seeds of buckwheat (upto 20,5 kg), wheat, millet, oats, Setaria, Chenopodium, Caragana (upto 1.4 kg) and branches of wormwood have been found. Oats are preferred to wheat as a feed (LAVRINENKO & TARASOV, 1967). Usually the stores contain only one type of food. Storing of food begins in the middle of August and continues upto the middle of autumn and sometimes even upto winter. All animals of this species take part in the storing; very often adult animals are seen collecting food items with the help of their juvenile offspring. All members of a family group spend the winter together in the same burrow (FETISOV & MOSKOVSKIKH, 1948).

The most important items of summer food are the green parts of hemp, Chenopodium, buckwheat, Atriplex, Artaphaxis scoparia and other plants (LEONTJEV, 1954).

The Burrows in summer and winter

The nesting burrow of the clawed gerbil is not very complicated in structure. Its length is usually 5 to 6 m (sometimes upto 14 m) and there are usually 5 to 10 entrances. The nest chambers are usually situated at depths of 40-45 cm in th summer burrows and at dephts of 110-150 cm in the winter burrows (Fig. 25). The majority of the tunnels are not very deep. The size of a nest-chamber is usually 15 to 40 x 13 to 20 cm. The nest is built of leaves and shoots of plants along with some hair and feathers and sometimes rubbish. The nesting burrow is surrounded by temporary burrows in a radius of 10 to 20 m. There are usually 1 to 3 entrances to each temporary burrow and sometimes there are small chambers where the remains of food may be found. The length of the temporary burrow is not more than 2 to 4 m (LEONTJEV, 1954). The clawed gerbil often uses the burrows of Microtus brandti.

Burrow of Meriones unguiculatus

Fig. 25. Burrows of clawed gerbil. I. summer-burrow; II. winter-burrow (after LEONTJEV, 1954). 1. dwelling nest; 2. deserted nest; 3. empty chamber; 4. food stores; 5. entrances (arabic numerals indicate depth in cm).


Reproductive Activity

In favourable years reproductive activity in Zabaikalie begins in February-March and ends in September or somewhat later. In February, 90 per cent of the females examined were pregnant, 13 to 27 per cent were found pregnant in March, 38 to 50 per cent in April-May, 30 to 33 per cent in June, 0 per cent in July and 0 to 33 per cent in August-September. Apparently, in some year, the adult females have upto 3 litters each, and the young members of the first of these litters also take part in reproductive activity. In Mongolia the breeding season is shorter. The females seem to have two litters per year there, with a few having a third one (in September): The litter size varies from 2 to 11 (average 6.4): The gestation period is of 29 to 30 days duration while lactation continues for 20 to 25 days.

Young M. unguiculatus weigh 3 g at birth, 7 g at 10 days of age, 23 g when a month old, 40 to 41 g at 2 months, 46 g at 3 months and 48-60 g at 5 months of age. The animals born in spring attain a body weight of 60-70 g and a body length of 110-120 cm by autumn. Summer born animals also attain similar body weight and length by spring (LEONTJEV, 1954).

Daily Activity

In summer these animals are active during the day as well as at night (Fig. 26). They are, however, not active during the middle of the day in July which is the hot part of the year. In spring and in autumn they are not active in cold nights. When the weather is cold and windy they do not leave their burrows and eat their stored food. In winter they appear on the surface only in warm sunny days. They are seen to be most active during periods of reproduction and storing of food. (LEONTJEV, 1962). Their daily run in summer is of the order of 1.2 to 1.8 km (BANNIKOV, 1954). One marked animal moved over a distance of 50 km. Movements over distances of 15 to 20 km from their home burrows have been recorded (NEKIPELOV, 1959).

activity of gerbils

Fig. 26. Daily activity of clawed gerbil (after LEONTJEV, 1954). Sequence of months shown from the top to the buttom: May, June, July, August, September. (ordinate: number of animals seen on the surface; abscissa: hours of the day).


Social Behaviour

In early spring the clawed gerbils are rather silent. In November their whistles can often be heard; the whistles are similar to those of Ochotona daurica, only somewhat softer and more melodious. If there is some danger they give signals to each other by thumping their hind legs like the great gerbil.

In south-eastern Zabaikalie from 1 to 3 adult males and from 2-7 females have been caught from the same burrow in summer. So the total number of animals living in a burrow varied from 3 to 14. They spend the winter also in such groups consisting usually of parents and their latest litter. Observations indicated that the animals may visit some neighbouring nest burrows, which are sometimes found to be interconnected. So, as in case of great gerbils, the clawed gerbils also do not live in small family groups but in somewhat larger groups which may consist of some adult males, females, subadult and young ones of different generations. But a 'stranger' to the group is persecuted. When bred in captivity, these gerbils often bite to death any unknown animals introduced in their cage (LEONTJEV, 1954).


Ecology and nutrition in different areas

In the Altaian Gobi the Mongolian gerbils live in semi-deserts with cereal and Salsola plants and in the overgrowth of Lycium. They are common in the ravines. In the Zaaltaian Gobi they are found in the oases and on sand dunes overgrown with Nitraria sibirica. They are however most numerous in the vallies of rivers, near crop fields, around human settlemnts and in rubbish heaps (TARASOV, 1958).

The gerbil has been observed in a flat, barren steppe to the south of the Tannu-Ola range. In north western Mongolia they avoid sandy barkhans but are quite numerous on flat Salsola plains (50 inhabited burrows have been recorded per hectare (NEKIPELOV; 1959).

In south eastern Zabaikalie it feeds mainly on Alhagi kirghisorum and Corispermum duriuscula, which grow on the abandoned range of Microtus brandti. As the vegetation begins to change with the season, they begin to eat wild cereals which, however, do not satisfy their needs. The stores of food here consists partly of shoots of wormwood and Suaeda, and partly of Eragrostis pilosa.

The Mongolian gerbil, which was not found in the steppes of Zabaikalie up to 1939, seems to have lived here since long. The species evidently spread from its original habitat (The banks of brackish water lakes) to the overgrowths of weeds on the fields and near human settlementd, where a considerable number of them were found in 1952, 1953 and 1958

Mobility, Migration and Mixing in Populations

According to marking data on clawed gerbils obtained in south-eastern Zabaikalie, they are very mobile species, so much so, that the population of different burrows mix intensively in summer and in autumn. This interesting information could be obtained after a relatively low number of animals were captured repeatedly, revealing as much as 10 to 32 per cent fluctuations in the population of adult males, 18 to 52 per cent in that of adult females and 22 to 28 per cent in the number of the young. A similar situation was found to hold true in respect of the percentage of animals captured for the first time in any particular burrow during March-August, 1958. This varied from 72 to 89 per cent of the otal catch. In 43 per cent of the burrows from 1 to 6 animals could be captured during 120 days, in 44 per cent burrows from 7 to 16, and in 13 per cent burrows from 17 to 22. The largest number of animals was caught in the largest burrows or in those which were situated on the path of migration.

The potential longevity of these gerbils is approximately (or a little more than) 2 years. A marked adult female was caught for the second time after nearly a year i.e. after she had spent her second winter. However, the mean life span of this species may not be more than 3 to 4 months. This would mean that an entire population is replaced within a year (LEONTJEV, 1962).

The movements of marked gerbils have not been found to be directed and never exceeding the limits of their range spread over 700 m. The use of the same burrow for the maximum period was found to be as follows: for an adult female - from May to August, for an adult male - from March to June and for a young female - for 3.5 months. However, long movements of these gerbils along roads, sometimes covering 40 km (Village Solovievka-Borsa) are on record (LEONTJEV, 1962).


[...]



*): This article concerning Mongolian Gerbils is only a part of the chapter and thankfully taken from the book:

"RODENTS IN DESERT ENVIRONMENTS",
ed. by I. PRAKASH & P. K. GHOSH,

DR. W. JUNK b.v. PUBLISHERS THE HAGUE 1975,
ISBN 9061930804.


If someone can get this book, I strongly would recommend reading the many interesting articles about several gerbil and some other species too. It is one of the rare sources in English, which also reviews many of the articles else only available in Russian language.

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Mongolian Gerbils in the Wild (Gerbils in the Inner Mongolia, by G. Agren, Zhou Q & Zhong W. 1989, reviewed by Julian Barker)
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