Dog Copulatory Behaviour - Anatomy & Physiology

First Stage Coitus - The Tie

Bitch in Oestrus spots bloody fluid just before the receptive stage.
Male identifies the female.
- Dogs are very aware of a bitch in oestrus and can detect them from 500-600 meters away.
Bitch adopts receptive posture ('stands') with the tail deviated to one side ('flagging').
Dog mounts and thrusts to achieve intromission.
- Intromission with a partially erect penis aided by the Os Penis
Vulval erectile tissue of the bitch grips the bulbus glandis of the penis.
Penis achieves full erection (the 'Tie')
Lasts 1-2 minutes
First and second fractions of semen are ejaculated.

Shortly after ejaculation, the dog dismounts and turns around while lifting one hind leg over the bitch.
The male and female remain 'tied' because the bulbus glandis of the penis remains engorged with blood.
Contractions of muscles near the base of the penis prevent venous outflow of blood from the bulbus glandis.
Sphincter muscles of the vulva constrict
- Compresses dorsal veins of the penis.
- Prevents venous outflow.

After the turn,they stand with their hind quarters in contact and their heads facing opposite directions.
Third fraction of semen is ejaculated.
Lasts 5-45 minutes
Encourages uterine rather than vaginal insemination.
Dog steadily ejaculates up to 30ml seminal fluid.
- Delivered through the Cervix to the Uterus.
- Forces the sperm-rich fraction into the Uterus.