Lordosis Behavior

Lordosis behavior, or mammalian lordosis, is a physical sexual posture seen in female mammals, including mice, cats and many others, the primary characteristic of which is a ventral arching of the spine. During lordosis, the spine curves so that the apex points in the ventral direction. That is, the spine arches inward toward the abdomen.

Lordosis can be seen during the mating process, both pre-copulation and/or during copulation. It may be seen as an invitation to mate. Lordosis aids in copulation, as it elevates the hips to allow for intercourse. It is commonly seen in female animals during estrus. It changes the pelvic tilt in an anterior way, with the posterior pelvis rising up, the bottom angling backward and the front angling downward.

During estrus (in heat) in mammals, the hormone estradiol (a hormone of the class of hormones known as estrogens) regulates this sexual receptivity behavior by the neurons in the ventromedial nucleus of the hypothalamus, the periaqueductal gray, and other areas of the brain. Sexual stimuli trigger activity in a number of brain areas, including the ventromedial hypothalamus, which sends impulses down axons synapsing with neurons in the periaqueductal gray. These convey an impulse to neurons in the medullary reticular formation which project down the reticulospinal tract and synapse with afferent neurons in the spinal cord (L1-L6) which contract muscles along the spine to exhibit the lordosis posture. Since these afferent neurons are also part of a reflex arc, lordosis can also be triggered reflexively.

The anthropologist Helen Fisher speculates that when a human female wears high-heeled footwear the buttocks thrust out and the back arches into a pose that simulates lordosis behavior, which is why high heels are considered "sexy".

• Lordosis behavior in copulating swine.