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denning sites was influenced by type of soil, presence of cleared areas, and
availability of water. A secluded island in the Kansas River was a favoured
breeding area In the years when it was easily accessible; four Or five dens were
used at the same time within its 53 acres. In North Lawrence one den was only
100 yards from an occupied house at the edge of the residential district. In the
course of study no definite evidence was found to indicate the use of a single
den by more than one family of foxes at the same time.
Examination of the reproductive tracts of males disclosed t they were
capable of breeding as early as late November. Most matings, probably occur in
January, and litters are born in March and April, after a gestation period of 53
days. The average size of eight litters reported from Kansas was 4.5 pups.
Young foxes grew rapidly during their first few months and attained nearly adult
size by the time they were five to six months old. Tracking provided information
as to the hunting habits of 3 species. The red fox forages individually in the late
sum-am) autumn, but hunts in pairs and family groups in winter spring. While
foraging in pairs, foxes used various maneuvers capturing pray that could not
have been employed by individuals.
Notes:
den берлога, логовище; пещера
mating спаривание
litter выводок, помет, приплод
gestation беременность
forage разыскивать пищу
Text 28
BANK OF EMBRYOS OF AGRICULTURAL ANIMALS
The Microbiology Institute of the Latvian USSR Academy of Sciences has
started a bank of embryos. This will make it possible reproduce in 20-30 years
any of the record milk cows of the Latvian brown breed in its direct progeny.
The embryos of pedigree cattle will be kept in laboratory t tubes for some
years at a temperature of 196° С below zero. n the need arises they will be
thawed out and implanted in the a productive cows, selected to carry "others"
calves. A record milk-giving cow only gives birth to 3-4 calves, but if the ovules
en from it are used, this number can be increased 10-fold in t to no time. It is
also planned to regulate the calves' sex which is important for the rational
formation of a herd.
Scientists intend to make the bank eventually the depository of the genetic
fund not only of the elite agricultural animals but also of wild animal в which
belong to rare or vanishing species.
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