IX.
Rats
A.
General Terms
1.
Male–Buck
2.
Female–Doe
3.
Young–Pups
B.
Breeding age
1.
Puberty
a.
100 days
b.
Male–300 grams
c.
Female–200 grams
2.
Reproductive lifespan
a.
1 year
C.
Cyclicity
1.
Type and Season of Cycle
a.
Polyestrous
b.
Year around
2.
Length of Sexual Cycle
a.
4-6 days
b.
Pseudopregnancy–13 days
3.
Duration of Heat (Estrus)
a.
9-20 hours
4.
Time of Ovulation
a.
8-11 hours from onset of estrus
5.
Viability of Ova
a.
8-12 hours
D. Mating
1. Precopulatory
a. Female
i. Lordosis
b. Male
i. Nibbling at female’s head
ii. Examination of females urogenital region
2. Copulatory
a. Mounting of male
b. Male clasps his forelegs about females laterolumbar region
c. Male palpates her sides with rapid movements of forelimbs
d. Simultaneous piston-like thrusts of pelvic region
e. Backward lunge is indicative of successful intromission
i. 3-44 intromissions precede ejaculation
ii. 2-9 pelvic thrusts per intromission
iii. Each intromission lasts 0.3-0.6 sec.
f. Ejaculatory intromission is prolonged and backward lunge is ommited
g. Satiation is not reached until 3-10 ejaculations
i. 3 hours in total time
h. Plug forms in vagina of female.
E.
Pregnancy
1.
Gestation–22 days
F.
Parturition/Lactation
1.
Parturition
a.
Pupping
b.
Nesting
2.
Littersize
a.
6-9 pups
3.
Mammary Glands
a.
12
b.
2 ventrolateral series along thoracic and inguinal regions
4.
Weaning age
a. 3 weeks
