The reproductive anatomy of the male cat, or tom, includes tiny, backward-facing projections on the penis. This feature is shared across most species of the Felidae family, including the domestic cat. This specialized anatomical feature is directly tied to the feline reproductive cycle. This arrangement serves a precise function, ensuring the continuation of the species through a specialized mating process.
Anatomy of the Penile Spines
The distinctive projections found on the male cat’s penis are technically described as penile papillae or spines. These structures are not made of bone, but are composed of keratin, which is the same tough, fibrous protein that forms a cat’s claws, hair, and the rough texture on its tongue. There are typically around 100 to 120 of these tiny, pointed structures located near the tip of the glans penis.
These papillae are small, horny cones that point backward toward the base of the penis. This backward direction is significant for their function during the mating process. They are not present in kittens, only beginning to develop when the male cat reaches puberty, usually around 12 weeks of age, and becoming fully developed by about eight months.
The Biological Necessity for Barbs
The existence of these specialized spines is a direct result of the female cat’s unique reproductive biology. Female cats, or queens, are classified as “induced ovulators,” meaning they do not release an egg automatically on a regular cycle. Instead, ovulation must be physically triggered by the act of mating itself.
The penile spines provide the necessary stimulation within the queen’s reproductive tract during copulation. As the male withdraws, the spines rake the walls of the vagina, sending a crucial neuroendocrine signal to the brain. This physical stimulus causes the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus.
The release of GnRH quickly results in a surge of Luteinizing Hormone (LH), which prompts the ovaries to release an egg. Without this intense stimulation provided by the keratinized spines, the queen would often fail to ovulate. The intensity of the stimulus directly influences the magnitude of the LH surge, meaning multiple brief copulations are common to ensure ovulation.
This mechanism explains why feline copulation is notably brief and often accompanied by a distinct, loud vocalization from the queen upon withdrawal. This reaction is due to the intense physical sensation. The spines ensure that the female’s body is prepared for fertilization immediately following the act, ensuring reproductive efficiency in a species where mating opportunities may be infrequent.
How Neutering Changes the Spines
The development and long-term maintenance of the penile spines are entirely dependent on the presence of the male sex hormone, testosterone. Testosterone is produced primarily by the testicles, which are removed during the neutering procedure, or castration. The removal of this source causes a significant drop in the cat’s androgen levels.
When a male cat is castrated, the penile spines begin to regress and atrophy due to the lack of hormonal support. The spines typically start to disappear within two weeks and are fully regressed or completely undetectable within six to eight weeks after the procedure. For cats neutered before puberty, the spines never develop at all.
The absence of these structures in a neutered adult cat serves as a physical indicator of their hormonal status. Veterinarians sometimes check for the presence or absence of penile spines when determining if a male cat has been neutered or if a retained testicle is present. The regression confirms that the primary source of testosterone has been removed.