Significant factors limiting the number of yellow squirrel, consider the activity of birds (buzzards, buzzard, steppe eagle) and tetrapods (polecat, fox, Korsak, Wolf) predators, and the effect of ecto-and endoparasites and they spread diseases. In addition, the dynamics of the ground squirrel with a year only one crop will depend on the intensity of their reproduction – delay the onset of sexual maturity, litter size, and is particularly noticeable on the number of females participating in reproduction. The timing of sexual maturity of females are more prolific relatively minor forms of ground squirrels from the southern and south-eastern regions of the species. Apparently, this fact can be explained by the relatively accelerated pace of recovery in the population numbers of yellow squirrel and his intense settlement in this part of the range.
The main factors affecting the course of the breeding period are coming out of hibernation: meteorological conditions this period, and biological factors of the previous year, necessitating a degree of fatness gophers during their care in hibernation.
Dates of awakening considered one of the decisive factors in determining the intensity of reproduction. For example, the spring 1954 in Muyunkum and in Yulsnom Balkhash was late: March of this year is colder than in February 1953 to delay the release of gophers. In Muyunkum animals come out of hibernation in 1954 on March 25 instead of March 2, 1953, in South Lake Balkhash – March 20 instead of February 27. All this affected the course of propagation, greatly reduce the number of pregnant females.
The influence of meteorological factors on fertility in the period when the gophers out of hibernation as a huge, and this factor closely intertwined with the above. Relatively large (36%) females proholostanie squirrels on the island Barsakelmes noted in 1945, when the March blizzard adversely affected the lives of animals. Coming out of the ground squirrel burrows were deprived of feed available to them and a few individuals with a refuge from the cold snow drifts or in hastily dug holes. Some individuals had time to close the hole from the inside stopper and did not come out, and some were killed in holes filled with water. During spring snowstorms animals noticeably thinner. As a result of prolonged fasting gophers there was a mass resorption of embryos in the early stages of development. Reduce the average number of embryos per female.
Influence the course of propagation of yellow squirrel have also biological factors of the previous year, in particular the state of vegetation. In favorable years in the forage is more amicable occurrence of both adults and young squirrels. Unanimous and simultaneous occurrence affects the waking animals in the spring. In this year of yellow squirrel in some parts of Kazakhstan was in 1946, in South Lake Balkhash and Muyunkum – 1953, 1955., When there was almost simultaneous awakening of rodents in many parts opromysh-lyaemogo array.