New Iberia enterprise and independent observer. (New Iberia, La.) 1902-1944, 1912-08-10

LedCS 1TtquEuLly Oono
oped. The black rat and the ROOT
rat have only 10 mammae-2 pairs
of pectoral and 3 pairs of inguinal
with but little tendency to vary.
Records of actual observations on
the number of young confirm the
deductions that might be drawn
from the above facts. At Bonn
bay, India, during the recent in
vestigations made by the India
Plague Commission, $1,000 rats
were trapped and examined. The
average number of embryos found
in pregnant brown rats was 81;
the highest number, IA. The ave
rage for the black rat was 5.2;
the largest number, 9.
In temperate ATTITUDES the aver
age number of young produced by
the brown rat Is undoubtedly
greater. Instances of very large
Filters observed in England are
recorded in The Field (London).
In two instances % and % young,
respectively, were found in a SIN
gle nest, though no evidence IS Of
fered that these were the progeny
of a single female; but in two
other cases II and 10 embryos
were found in gravid females. A
dealer in feedstuffs in Washing
ton, D. c., relates that he found
10 young rats in a single nest IN
his store. Within the past few
months the writer has examined
four pregnant brown rats taken
in traps. The numbers Of en-
bryos they contained were 10, IL,
- and 10, respectively. While
we have not enough data for def
mite conclusions, we may safely
state that the average litter for
this latitude is not less than III.
Frank T. auckland, in Curios-
tiles Of Natural History, relates
that a white rat which he kept in
captivity gave birth to II young
when only eight weeks old. AS
CESSATION in rats occupies three
weeks, this animal just have bred
when oily five weeks old.
The number Of times rats breed
in a year is not definitely known,
and probably varies considerably
with local conditions, Kolazy
makes the almost incredible state
ment that two female white rats,
kept by him in confinement and
well fed, within thirteen months
gave birth to 26 filters of young,
numbering $50 in all. One of
them produced young regularly at
intervals of 25 days.
The writer recently kept two
young female brown rats with
male in a large open cage for sew
eral months. One Of the female
gave birth to young on April Is;
the other on April II. The num-
Der in these litters was not OBJ
served, as some were devoured
soon after birth, and all within
three days, presumably by the
male rat. On May %, both fe-
males gave birth to young, "a
in number, all in one nest.
The known facts concerning
the breeding Of the brown rat may |
be briefly summarized as follows:
The animals breed from three to
five times a year, each time bring
ing forth from 6 to 10 young. AZ
ter a CESSATION period Of twenty
one days, the females give birth
to their young in nests built in !
underground burrows or under
floors, stacks, lumber, woodpiles,
or other shelter. The young are
blind and naked when born, but
grow rapidly, and young females
are capable of breeding when less
than three months old.
Early spring and summer are
the periods Of greatest reproduc-
tive activity among rats. Young,
however, are to be found every
month of the year.
The above statements apply in
the main also to the black and the
roof rat, but the number Of young
in a litter is somewhat smaller.
The newly born young Of the
black rat have not the bright pink
color of those Of the brown and
the roof rat, but are blush, espec-
tally ON the upper parts. Black
and-white spotted rats are at first
bluish-and-red spotted, the red
areas representing the white OF
the adults.
ITO be continued next weekly