The most frequently bears are born in the second or third week of January, but even within the same region may be significant deviations from these terms. In the area of the reserve, we know Tsentralnolesnogo births cubs in mid-December, and one of caught in the middle of February tiger was pregnant.
In the North-West of the USSR cubs are born in January and February, and in some areas, such as Murmansk, there are cases of young born in March (Danilov, 1979). In terms of the Moscow zoo mating different pairs in different years may vary, but usually occur in May-June, pregnancy lasts 230-240 days, and the birth of the young is in December-February, . There are other details of the zoo: the pregnancy 195 — 210 days, and delivery to the end of December and January (Danilov, 1979). In Leningrad Zoo bears the pregnancy from 152 to 227 days.
Found that the timing of mating affect the duration of pregnancy in late coverage of females during pregnancy decreased (Danilov, 1979). There are also reports of repeated pairings bear in the Moscow zoo, but the timing of birth of the cubs were independent.
The date of mating and birth of young bears, we consider the example of the Kiev Zoo, cubs females were taken there every year, so, too, pairing occurs annually (Table 15).
The Kiev Zoo bears mate repeatedly throughout this period, while the baby and Dolls in 1981, from April 7 to July 19, the pairing was observed daily. In 1982 Kiopa bore four cubs. With her in the den was closed female Matilda, who had no cubs. Matilda sometimes drags the some of the cubs to her, but he began to cry, and Kiopa took away the baby to her. NC fights for cubs between females was not.
In 1982, Harry and mated both bear and gave birth to each of 4 bear in one den. Females behave peacefully. Cubs they took on February 25.
Similar behavior was observed in the Moscow Zoo (Gulyaev, 1934), when females lay Zoe and Bert together in a snow pit. January 8 Zoe gave birth to two cubs. Bertha treated them like a mother. Females were separated. Zoe placed with cubs in a separate cage, but she did not pay any attention to the children, and Bertha strongly clung to him. Females again united. Burt was to take care of the kids, nest, and Zoya We finally focus on their children. In the nest the female legln muzzle to muzzle, and bears are located between them. January 16 bore Bertha. Female ward of the cubs was impossible. 18 and 21 January Zoe Bears fell. Interestingly, the pairing of these females with two males in May 1932, was inconclusive — no offspring, while mating with a male, they gave the breed.
After the release of the bear dens are able to distinguish foreign from their offspring by smell, and possibly in appearance. Combining raznosemeynyh bears in one family with a mother-bear-is unlikely. For black bear (Ursus arnerikanus L.) against natural "adoption" is not registered (as radiotropleniya). Of the 24 planted in 22 different dens cubs were taken by females. Of orphaned bear cubs, a lift to the family during its exit from the den, and after the family left it, was passed only one. Malorezultativnymi podsazhivaniya orphaned cubs were captured and immobilized by a she-bear-mothers: of 5 podsazhennyh cubs was passed only one [257, 262].
These examples show that those in the den females did not differ from others their young, and their maternal behavior applies to all babies equally.
In nature, there are cases of occurrence in one den several bears.  The most likely occurrence relatives familiar with the smell of each other. The female in this group may be pregnant, although many researchers deny this possibility. Known case of being in one den females, three cubs and mentors (Dulkeyt, 1964).
Tolerant, and especially caring for the newborn in the den is, apparently, an original adaptation of the species  providing the best survival of offspring.
Adaptation should be considered as an element of complex biological forms of maternal behavior as expressed in individuals of both sexes and is manifested not only in finding the family in the den, but after getting out of it.
On the existence of caring nurses, mentors in the bear family is well known [25, 31, 128, etc.], but generally it is a rare phenomenon. In recent years in the area of the reserve Tsentralnolesnogo we were able to observe 3 family of bears with mentors in the first and the second was at 2 and 3 in the third yearlings (the female of the last of the family had a width of plantar callosities 12 cm).
The third family was registered by us in 1985 in the village. Zamoshye. In 1984, here we have found a bear (the width of the plantar calluses 12 cm) with three cubs, Lonchakov. It is likely that in 1985, it was the same bear with offspring in 1985 and mentors, born in 1983, careful troplenie this family for 5 days did not allow us to identify any specific behaviors bear mothers and mentors to to yearlings.
Watching over the years for family groups of bears, we did not find anything special females in relation to the young ones who would talk about the special protection of the young (in July and August) or the activities to his training.
The behavior of all members of families with mentors were also common.
In all known cases, the bears caught in dens, it was found to bear three or embryo (Table 16).
Should be stressed that throughout the period of field work from 1970 to 1986 of registrations with the three bears and a little bear, and the family with four cubs, yearlings, we registered only once in 1973