Lordosis behavior (), also known as mammalian lordosis (Greek lordōsis, from lordos "bent backward") or presenting, is the naturally occurring body posture for sexual receptivity to copulation present in females of most mammals including rodents, elephants, and cats. The primary characteristics of the behavior are a lowering of the forelimbs but with the rear limbs extended and hips raised, ventral arching of the spine and a raising, or sideward displacement, of the tail. During lordosis, the spine curves dorsoventrally so that its apex points towards the abdomen. Description Lordosis is a reflex action that causes many non-primate female mammals to adopt a body position that is often crucial to reproductive behavior. The posture moves the pelvic tilt in an anterior direction, with the posterior pelvis rising up, the bottom angling backward and the front angling downward. Lordosis aids in copulation as it elevates the hips, thereby facilitating penetration by the penis. It is commonly seen in female mammals during estrus (being "in heat"). Lordosis occurs during copulation itself and in some species, like the cat, during pre-copulatory behavior. Neurobiology The lordosis reflex arc is hardwired in the spinal cord, at the level of the lumbar and sacral vertebrae (L1, L2, L5, L6 and S1). In the brain, several regions modulate the lordosis reflex. The vestibular nuclei and the cerebellum, via the vestibular tract, send information which makes it possible to coordinate the lordosis reflex with postural balance. More importantly, the ventromedial hypothalamus sends projections that inhibit the reflex at the spinal level, so it is not activated at all times. Sex hormones control reproduction and coordinate sexual activity with the physiological state. Schematically, at the breeding season, and when an ovum is available, hormones (especially estrogen) simultaneously induce ovulation and estrus (heat). Under the action of estrogen in the hypothalamus, the lordosis reflex is uninhibited. The female is ready for copulation and fertilization. When a male mammal mounts the female, tactile stimuli on the flanks, the perineum and the rump of the female are transmitted via the sensory nerves in the spinal cord. In the spinal cord and lower brainstem, they are integrated with the information coming from the brain, and then, in general, a nerve impulse is transmitted to the muscles via the motor nerves. The contraction of the longissimus and transverso-spinalis muscles causes the ventral arching of the vertebral column. Hormonal and cerebral regulation Sexual behaviour is optimized