I know that this is not exactly a forum for discussing animal behaviour but I get the feeling there seems to be some confusion with regarding to the phenomenon of musth in elephants ( see Sabyasachi’s post Dancing Elephants ) and I felt that perhaps I could shed some light on the same.
I guess it is no secret to the members of Indiawilds that elephants are one of my favorite animals and I can spend hours watching a herd peacefully grazing. These animals are extremely social and observing the interaction between individuals is what prompts me to spend so much time with them. One of the aspects of elephant behaviour that fascinates me is their mating game. I would like to share some of my knowledge derived as much from reading about them as observing them. What ever I read I tried to relate to what I saw with the end result that I ended up spending even more time with them much, I am sorry to admit, to the sorrow and frustration of the tourists who happened to be with me on safari.
Puberty in a female elephant can be described as the age at which she experiences her first estrus cycle while sexual maturity can be considered as the time of the first ovulation. There may be a difference of two to four years between the two. A female elephant reaches sexual maturity between the ages of eleven to fourteen years. However I would like to point out that there is a wide difference between populations in this regard as a result all figures quoted are relative.
They have an estrous cycle of fourteen to sixteen weeks, however an elephant can only conceive during two to four days during this cycle. So a male has to be present at the right place at the right time other wise he will have to wait for another sixteen weeks. To better understand the estrous cycle of an elephant let us first take a look at the typical estrous cycle of mammals.
The first phase is called the follicular phase with the growth of the vesicular ovarian follicles containing the egg. The second is ovulation that i.e. the release of the eggs into the fallopian tube followed by the luteal phase when the corpus luteum is formed inside the ruptured follide and finally if the egg is not fertilized the degeneration of the corpus luteum to start a new follicular phase.
In elephants there are two or more follicular waves the last of which only results in ovulation. The first follicular wave does not lead to ovulation and is succeeded by another follicular wave. This unique system serves in sending an early signal to a male as to the impeding ovulation in a female thus maintaining his interest with one family group for a while. This ensures that he does not miss an opportunity to mate. This is one reason why a bull is sometimes seen associating with a particular family group for a while. As can be imagined the detection of estrous in females is very important. A female signals estrous with chemicals through urine and vaginal secretions while a male performs flehmen – uses the tip of his trunk to collect and convey the sample from the female to an organ on the roof of his mouth to test the chemical signals. The female also uses auditory aids i.e. a particular call in advertising estrous and also distinctive behavior which I would like to call flirting when desirable males are in the vicinity.
Courtship is short and can last for several hours to a day and mating lasts no more than a couple of minutes, they may mate several times over a period of one or more days. If successful there is a gestation period of twenty to twenty two months.
Puberty in male elephants can be described as the time of the first production of viable sperm and usually occurs between the ages of eight to fifteen years and sexual maturity when a dense mass of motile sperm is produced. As in the case of females there is usually a gap of two to three years between the two. Once again I would like to state that the age varies considerably between populations and the ages given are relative and are being quoted to give us a broad picture.
An interesting phenomenon in elephants is the phase of Musth that a male undergoes. Musth is a secondary sexual character used to attract females. But what exactly is musth ?
Musth is a post pubertal phenomenon in which after attainment of maturity there is a gradual build up in frequency, duration and intensity. Several factors influence this but the most important is the body condition of the individual. As a result that in young bulls (between the approximate ages of fifteen to twenty five years) the intensity and duration of musth is relatively short lasting from a few days to a month.
During the early stages of musth the temporal glands (these are modified sweat glands located between the ears and the eyes) swell slightly and are visible as dark patches. The secretion from these glands is watery and flows down the cheeks. The chemical composition of this is different from the secretion during full musth and it lacks the pungent odor of the latter. The musth in young bulls usually does not progress beyond this stage.
During the full musth stage, which occur in the older bulls and follows the early stage, the temporal glands swell considerably and the secretion is pungent and more viscous and stain a wide area of the cheeks and sometimes flow down to the corners of the mouth. The animal also starts dribbling urine as drops or in a regular stream. This it does even when its penis is sheathed resulting in urine running down its legs and staining them. The urine is smelly and has a particular odor. One can smell an elephant in full musth.
An elephant in musth will very often walk with his head held high and ears spread wide. They sometimes press their tusks against embankments and also against the bottom of small pools resulting in more pronounced temporal gland secretion. They also rub their temporal glands against trees. While this is common even during the non musth phase, the frequency of temporal gland rubbing increases during musth. They emit low frequency rumbles called musth rumbles. All this along with the dribbling of urine is done to advertise the state of musth. Female elephants seem to actively seek out musth males and prefer to mate with them.
While individual bulls come into musth almost the same time every year (over a short span) different males show wide variation in the time of year when they come into musth. It has been observed in one population in South India that the younger bulls came into musth during the dry season while the older bulls came into musth during the wet season. The bulls generally become more aggressive towards other males during musth and musth also serves as a deterrent to rival males and may also influence female choice of mates. It was observed that the bigger and stronger bulls not in musth would make way to younger and smaller bulls in musth.
The possible explanation for this is that the older bulls time their musth when more number of females are in estrus i.e. during the wet season and younger bulls during the dry season so as not to expose themselves to the older bulls when there are in musth. It was also observed that when a young bull in musth encountered an older bull in musth it stopped showing the physical manifestation of musth thus avoiding conflict with the physically superior animal. This spacing of musth among individuals in a population is interesting and needs further understanding as it is also well know that the chemical composition of musth secretion varies between the younger and older bulls. Once again I would like to add that the timing of musth between older and younger bulls will vary between populations as a lot of factors influence it.
I have stated earlier that females actively seek out bulls in musth to mate with. What possible advantage could they derive from this? As body condition is the most important factor in influencing musth it stands to reason that only males of high genetic quality come into full musth. This could be the reason why a physically superior bull not in musth will make way to a smaller animal in musth, it would not like to sustain an injury that may have a negative impact on its coming into musth later. Musth is an expensive proposition for male elephants in physiological costs as they end their musth phase in very poor condition. The high levels of testosterone during the musth phase seriously affect the functioning of the immune system. Thus an elephant in musth is probably at the height of its physical condition and is proving this to females by advertising his ability to take severe punishment thus making him desirable as a mate as the females wish to pass on the healthiest genes to their offspring.
Another secondary sexual character in male elephants is the presence of tusks. Tusk size and rate of growth varies among individuals and are thus not a reliable factor in aging elephants in fact after a certain size become handicaps. They however grow in size through out the life of elephants. Tusks are really not very beneficial except as aids in debarking trees to obtain nutrition so what role do they play?
Elephants with longer tusks have correspondingly smaller body sizes. And as body size and condition influences musth in elephants it stands to reason that long tusked males will be at a disadvantage. If that is the case then why should an individual invest so much nutrition in growing long tusks?
( continued in the Part -2 please read as a whole )