The pineal gland is found deep within the brain (see diagram 16.4). It is sometimes known as the ‘third eye” as it responds to light and day length. It produces the hormone melatonin, which influences the development of sexual maturity and the seasonality of breeding and hibernation. Bright light inhibits melatonin secretion Low level of melatonin in bright light makes one feel good and this increases fertility. High level of melatonin in dim light makes an animal tired and depressed and therefore causes low fertility in animals.
Diagram 16.4 - The pineal gland