Just so more bits and pieces of info I didn't want to lose track of...

1.      Anogenital distance

·        Genital opening to anus

·        Distance relative to hormones pup was exposed to during development

·        Males have a larger distance due to an increased testosterone exposure

2.      Anogenital statistic

·        Anogenital distance (mm) divided by weight (g)

·        Can predict males and females

3.      Rat reproductive system and environmental components on behavior

·        21 day gestation in the rat; 1^st trimester is 7 days

·        During 1^st trimester, sexual differentiation is ambiguous, that is, the pups are bipotential for sex.  Sex is set in the following trimesters.

·      Environment effects the degree of maleness of femaleness in the pup.  Neighboring fetal pups and hormonal exposure shape development.  There is a position effect of hormones on growth and development within the uterine horn.  The uterine horn holds the pups next to each other in a common placenta.

4.      Rat sexual behavior

·         Female proceptive behaviors – hopping and darting, travel and kick, ultrasonic singing and ear wiggling. The female typically initiates mating.

·         Female receptive behaviors – lordosis (reflexive female mating posture - back arched down, rump up, and tail to the side, which physically rotates the vulva to a backward facing position), the stereotypical arching of the back in an inverted manner with head and hindquarters elevated.

·         Male pre-copulatory behaviors – stereotypical grooming and washing, investigating female for chemical cues.

·         Male copulatory behaviors – mounting (male's copulatory position), intromissions, and ejaculation.  The value of intromissions is believed to be the stimulation of egg release.

·         Post-ejaculatory interval – the refractory interval following copulation.  This period of rest or inactivity after ejaculation is displayed by both sexes.  In the male, it lasts 5 – 10 minutes.  In the female, it lasts 30 seconds – 1 minute.  This promotes polyandrous reproduction.

·         Male rats have a tonic hormone secretion, which stays fairly constant.  Female rats have a cyclic hormone secretion.  She will mate at the peak of the hormone curve or estrus.  The estrus cycle is 4 days in length.

References:

http://www.spflrc.org/user/rats/Glossary.htm

http://www.spflrc.org/user/rats/norway_rat_ethogram.htm

Lange, Gary. Ethology Lecture. Saginaw Valley State University.