The physiology of polar bear mating (Ursus maritimus)
Authors: Nikitin Georgy , Malev Alexander , Batrakov Alexey 
Published: May 2022

The well‐being of any species depends on successful reproduction, so the study of mating is essential, mainly to prevent the extinction of rare animals. In the process of evolution, each new species has adapted to environmental conditions in the struggle for survival through the morphological and physiological characteristics of the reproductive anatomy. Polar bear mating lasts 10‐20 minutes and corresponds to uterine insemination, but the description of the physiology of polar bear mating is lacking due to technical difficulties. Studies of the penis of a polar bear during an erection caused by the impact of electrical impulses of an electro‐ejaculator on the pudendal and external spermatic nerves and smooth muscles of the genital organs before reaching ejaculation to obtain sperm suggest how this happens. We studied the manifestation of sexual reflexes in a male polar bear (Ursus maritimus), age 10 years. The bear was kept in the Kazan Zoo from birth and did not participate in mating. An electro‐ejaculator was used to collect sperm. We have established the following features: the penis was covered entirely with a prepuce (praeputium) in a not erect state. The length of the penis is 19 cm. It practically does not change due to the presence of the os penis, which is 18.6 cm long and extends into the head of the penis. The diameter of the body of the penis is 1.5 cm. Initially, the head was 2 cm in diameter, two plates stood out on it, filling with blood during an erection. The opening of the urogenital canal (canalis urogenitalis) extends with its free end outside the head and has soft processes at the end of the canal. The length of the processes of the free end of the canal is 6 mm, and the width of their bifurcation is 4 mm. During an erection, the shape and size of the body of the penis (corpus spondiosum glandis) change and increase. The spongy body of the glans penis swells like a conus from the main shaft with the broadest part at the end. It has a length of 4 cm. The upper part is like an ellipse inclined at an angle of 45 degrees to the plane of the cone. Further, the head of the penis (glans penis) increases and takes the form of a straight cone with swollen urogenital canal sponges about 20 mm long, 10 mm in diameter at the base, 15 mm at the end. In the upper part, the funnel has an outer diameter of 40 mm, takes an angle of almost 90 degrees to the shaft of the penis, looks like a hand pump cuff. It can be assumed that the function of the swollen sponges is to ensure maximum passage of seminal fluid through the cervix, which is 15 mm long and opens during mating, and to prevent sperm leakage during insemination. They close the backflow of seminal fluid from the body of the uterus. During intercourse, the ejaculate pours into the vagina and partly irrigates the cervix. During coitus, it occurs from 3 involuntary muscle contractions of the body, which indicate stepped ejaculation (in portions). However, polar bears should be regarded as animals with uterine type of insemination, the highly swelling glans of the male penis, poorly covered by the walls of the vagina, acts on the principle of a piston. The penis pushes ejaculate from the vagina into the uterus.