User:Eb1002/Asian Elephant

Reproduction
Reproduction in Asian elephants can be attributed to the production and perception of signaling compounds called pheromones. These signals are transmitted through various bodily fluids. They are commonly released in urine but in males they are also found in special secretions from the temporal glands. Once integrated and perceived, these signals provide the receiver with information about the reproductive status of the sender. If both parties are ready to breed, reproductive ritualic behavior occurs and the process of sexual reproduction proceeds.

Bulls reach sexual maturity around the age of 12–15. Between the age of 10 and 20 years, bulls undergo an annual phenomenon known as "musth". Secretions containing pheromones occur during this period, from the paired temporal glands located on the head between the lateral edge of the eye and the base of the ear. During this period the testosterone level is up to 100 times greater than non-musth periods, and this can cause bulls to become aggressive. Some bulls will fight one another to get access to oestrus cows, however strong fights over access to females are extremely rare.The aggressive behaviors observed during musth can be attributed to varying amounts of frontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane) throughout the maturation process of bulls. Frontalin is a pheromone that was first isolated in bark beetles but can also be produced in the bulls of both Asian and African Elephants.The compound can be excreted through urine as well as through the temporal glands of the bull allowing signaling to occur. During musth, increased concentrations of frontalin in the bull's urine communicate the reproductive status of the bull to female elephants.

Similar to other mammals, hormone secretion in female elephants is regulated by an estrous cycle. This cycle is regulated by surges in Luteinizing Hormone that are observed 3 weeks from each other. This type of oestrus cycle has also been observed in African Elephants but not known to affect other mammals. The first surge in Luteinizing Hormone is not followed by the release of an egg from the ovaries. However, some female elephants still exhibit the expected mating protocols during this surge. Female elephants give ovulatory cues by utilizing sex pheromones. A principal component thereof, (Z)-7-dodecen-1-yl acetate, has also been found to be a sex pheromone in numerous species of insects. . In both insects and elephants, this chemical compound is used as an attractant to assist the mating process. In elephants, the chemical is secreted through urination and this aids in the attraction of bulls to mate. Once detected, the chemical stimulates the vomeronasal organ of the bull thus providing information on the maturity of the female.

Reproductive signaling exchange between male and female elephants are transmitted through olfactory cues in bodily fluids. In males, the increase in frontalin during musth heightens their sensitivity to the (Z)-7-dodecen-1-yl acetate produced by female elephants. Once perceived by receptors in the trunk, a sequence of ritualistic behaviors follow. The responses in males vary based on both the stage of development and the temperment of the elephant. This process of receiving and processing signals through the trunk is referred to as flehmen. The difference in body movements give cues to gauge if the male is interested in breeding with the female that produced the secretion. A bull that is ready to breed will move closer to the urine and in some cases an erection response is elicited. A bull that is not ready to breed will be timid and try to dissociate themselves from the signal.

In addition to reproductive communication, chemosensory signaling is used to facilitate same-sex interactions. When less developed males detect pheromones from a male in musth, they often retreat to avoid coming in contact with aggressive behaviors. Female elephants have also been seen to communicate with each other through pheromone in urine. The purpose of this type of intersex communication is still being investigated. However, there are clear differences in signaling strength and receiver response throughout different stages of the estrous cycle.

The gestation period is 18–22 months, and the cow gives birth to one calf, only occasionally twins. The calf is fully developed by the 19th month, but stays in the womb to grow so that it can reach its mother to feed. At birth, the calf weighs about 100 kg, and is suckled for up to three years. Once a female gives birth, she usually does not breed again until the first calf is weaned, resulting in a four to five-year birth interval. During this period, mother to calf communication primarily takes place through temporal means. However, male calves have been known to develop sex pheromone producing organs at a young age. Early maturity of the vomeronasal organ allows immature elephants to produce and receive pheromones. It is unlikely that the integration of these pheromones will result in a flehmen response in a calf. After they are weaned, females stay on with the herd while mature males are chased away.

Asian elephants reach adulthood at 17 years of age in both sexes. Average elephant life expectancy is 60 years in the wild and 80 in captivity, although this has been exaggerated in the past.

Generation length of the Asian elephant is 22 years.