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One of the many peculiarities of cats that is most striking is their tongue , covered with tiny spines, called spicules , directed backwards, which cause that rough and scratchy sensation when they lick someone.
But it is not the only spiny organ of cats.
Stranger still is his penis . Not only does it have the same type of spicules, also directed backwards, in addition, the limb is supported by a bone called a baculum .
It must be said that felines are not the only mammals with spicules on their penis ; they are also found in many other mammals, including hyenas, rodents, and most primates, including chimpanzees. The ancestors of the human being also had them, but they lost them.
But back to the cats.
The Anatomy of a Cat’s Penis
The external genital anatomy of the cat is quite strange . From the outset, his penis is not found extended across his belly and pointing forward, as in other mammals –dogs, horses, bulls…–. On the contrary, in cats, the penis is completely hidden within the foreskin, which is small and located immediately under the testicles, and faces backwards .
When the erection occurs, the baculum comes into play, this long and fine bone, surrounded by powerful muscles, which reorients the penis to place it forward . The glans, with a conical appearance and rounded tip, emerges from the foreskin, and that is where those characteristic spicules made of keratin are exhibited, the same component of the nails and hair of any mammal, including humans, and the same that makes up the spicules of the feline tongue. Depending on the specimen, it can have between 50 and 200 spicules.
The presence of spicules depends on hormones. When a male is castrated before sexual maturity, he does not develop spicules . When surgery is performed on adult males, the spicules gradually disappear, and at the same rate that sexual behavior decreases. But if testosterone is applied to a castrated male, he maintains spines, more the more testosterone he receives.
The spicules during copulation
In the mating season, the female cat is usually very sexually active , and one of the functions of the spicules is the removal of semen remains that may remain in the vagina, product of previous sexual encounters.
As the thorns are oriented backwards, the penetration happens without obstacles, but the withdrawal is more complicated. When carrying out the movements of copulation, the spicules slide inwards and scrape outwards, dragging any remaining foreign fluid from a previous copulation to the outside .
On the other hand, the spicules are seated on tactile corpuscles , and, therefore, their stimulation generates in the male a discharge of extra pleasure during intercourse that allows him to ejaculate quickly. This is an advantage for polygamous species, as they have more time to copulate with other individuals. In addition, it allows the cat to know the correct orientation only by touch.
Another evolutionary advantage that has been found is avoiding premature withdrawal . Until the male ejaculates, the penis does not relax and the spicules do not retract, so until that moment arrives, the male and female remain hooked and cannot be separated.
The characteristic sounds that the cat expresses during copulation could suggest that they express pain. However, the first investigations looking for a form of artificial insemination in cats carried out experiments with smooth probes and, when the probe reached 20 millimeters in depth, the cat made the same type of sounds.
The conformation of the cat’s vagina has two parts, an outer one, wide, and an inner one, much narrower. It is the distension of this second part of the vagina that induces the cat to emit those vocalizations that we hear during intercourse, and not the spicules. Whether or not the scraping of the spicules is painful for the female, although it is generally accepted, we do not know for sure.
The true function of the spicules
Although we do not know if this stimulus is painful, we do know that it plays an essential role in reproduction .
It has been proven that the scraping of the walls of the vagina generates in the female a discharge of luteinizing hormone (LH) by the pituitary gland. This hormone, common in all mammals, controls the maturation of the follicles, induces ovulation and, finally, the production of progesterone , which is the hormone that promotes pregnancy.
Furthermore, it is known that a single copulation is usually not enough . In this situation, barely one in five females ovulates, while with three copulations in a single day, four out of five ovulate.
REFERENCES:
Aronson, L. R. et al. 1967. Penile spines of the domestic cat: Their endocrine-behavior relations. The Anatomical Record, 157(1), 71-78. DOI: 10.1002/ar.1091570111
Cooper, K. K. 1972. Cutaneous mechanoreceptors of the glans penis of the cat. Physiology & Behavior, 8(5), 793-796. DOI: 10.1016/0031-9384(72)90285-5
Watson, P. F. et al. 1993. Vaginal anatomy of the domestic cat (Felis catus) in relation to copulation and artificial insemination. Journal of Reproduction andFertility. Supplement, 47, 355-359.
Wildt, D. E. et al. 1980. Effect of Copulatory Stimuli on Incidence of Ovulation and on Serum Luteinizing Hormone in the Cat*. Endocrinology, 107(4), 1212-1217. DOI: 10.1210/endo-107-4-1212
