Friday, 1 April 2022

Ukraine Part 4: Hamsters, Voles and others


Common Hamster preparing to attack

The Golden Hamster is a popular pet with children, although to be honest other rodents are better choices, and when I was a child we had a succession of them in the house. Definitely not suitable as a pet is the cavy sized (maximum 450g) Common Hamster Cricetus cricetus, which is notorious for a decidedly aggressive disposition. Try to pick one up and it will not sit placidly in your hand but rather try to bite it off. This is probably an inevitable result of being a handy sized meal for basically every carnivorous mammal or bird in Europe, and being decidedly territorial and solitary as well.

Common Hamsters despite their name are becoming increasingly uncommon, to the point of being classed as Critically Endangered. Their range before their recent decline extended from eastern France to Kazakhstan, and Poland to Georgia. A classic grassland animal, they adapted well to the rise of agriculture to the point of becoming a serious pest, and as a single hamster can store as much as 65kg of grain in the depths of its burrow then it easy to see how it has historically been persecuted. The recent rise of industrial agriculture however has had a serious effect, not least because modern crops tend to be cleaned of the agricultural weeds that are vital to its diet – in fact a lack of vitamin B3 in the diet due to living exclusively on maize is associated with behavioural abnormalities including infanticide.

In normal circumstances Common Hamsters live in a burrow that during the winter may be several metres deep. They prefer deep, heavy soils where burrow construction is easiest. Each hamster has its own burrow which it defends vigorously, only meeting another hamster to mate. After a very short pregnancy of only 18 days the female gives birth to up to 15 pups, although usually less, and in the course of a summer usually has two litters. Clearly maximum productivity is potentially very high, and they need to have this ability as foxes, mustelids, various raptors both diurnal and nocturnal, and probably many snakes will prey on them.

In Ukraine until the 1990’s Common Hamsters were widespread and common, especially in the forest steppe zone away from the drier soils of the south east. Densities reached up to 7 burrows per hectare. Since then there has been a major decline, and they are effectively extinct over much of the country. The chief reason for this is probably changes in agricultural crops – they much preferred alfalfa fields to cereals and decline in cattle with inevitable decline in need for alfalfa forage has removed habitat. Burning of fields and use of pesticides and herbicides has also removed much of their food and habitat.

Grey Dwarf Hamster

Also present in Ukraine is the much smaller Grey Dwarf Hamster, Cricetulus migratorius. A much smaller animal, it averages around 10cm long and 40g or so – about 1/10 of a Common Hamster. This is much more a dry country animal, living in areas of open vegetation and semi-desert, often at high altitudes and avoiding wetter areas. In many parts of its range, which extends east from Ukraine into western China and south into the Middle East it is associated with people, sometimes even living in houses, Unlike its giant relative it is listed as Least Concern, and as it is not so dependent on good farmland that state is unlikely to change. In other ways it is similar in behaviour, being a solitary animal living in burrows and making extensive stores of food for hard times.

Steppe Lemming

Much less solitary than hamsters are the so-called Steppe Lemmings Lagurus lagurus. Technically a vole, these tend to live in family groups with each family having a main domicile burrow with several entrances and a nesting chamber. Each family will stay close to the burrow, usually within 6m of their home. As with their Arctic counterparts they have extreme fluctuations in population, and can build up their numbers rapidly when conditions are good. As they can have six litters of up to seven young a year population explosions can occur, and when this happens large numbers will disperse in search of food in the form of seeds, bulbs and other plant material. Today it is an eastern species with Ukraine marking the western end of a range through Mongolia into China, but fossil remains show that in the cold and dry habitats south of the ice sheets during the Ice Ages its ranged extended as far west as the British Isles.

Tatra Vole

Many species of Microtus voles are found in grasslands and fields across Europe. Ukraine is home to six species, but one of the least known is the Tatra Vole Microtus tatricus. Ukraine and Romania share a unique subspecies M. tatricus zykovi. Unlike the previous species, this very much avoids farmland and is only known from natural habitats such as alpine meadows, often at high elevation.

Snow Vole

Living well away from the grassy fields of the lowlands, the Snow Vole Chionomys nivalis is an animal of rocky areas above the tree line. As with many small rodents it is mostly solitary and territorial and feeds on green plants, seeds and a few insects. They tend to use scree slopes and dig burrows among the rocks. They are active both by day and by night, and may bask in the sun on occasion. They have a wide range in European and Asian mountains, as far west as Portugal and as far east as Turkmenistan

Thick-tailed Three Toed Jerboa

Not related to the various members of the hamster and vole family, a Ukraine species that is hard to confuse with any other small rodent is the Thick-Tailed Three Toed Jerboa, Stylodipus telum. Growing to abody length of around 11 cm, with a tail as long again, the rather unwieldy name is at least descriptive of a species that has a method of locomotion that is instantly recognizable – they hop. They live in deserts and desertified steppes, and Ukraine is at the west end of their distribution which extends through central Asia into China. They live in complex burrows with multiple entrances/ exits. . The reproductive rate is low for a rodent, with only a single litter of up to six young each year. They are almost entirely nocturnal, leaving their burrows to hunt for seeds and insects. Although fairly widespread, the subspecies found in Ukraine S. telum falz-feini is fairly rare and at risk from agricultural development and pesticides.

Next time I will look at the remaining variety of rodents in Ukraine. The dormice and field mice

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