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Musth does not necessarily give younger, male Asian elephants an edge

Roving male: Ghatotgaja, a male aged above 45 years, sighted in musth. Temporal gland secretion is visible as a dark stain behind and slightly above the eye.

Roving male: Ghatotgaja, a male aged above 45 years, sighted in musth. Temporal gland secretion is visible as a dark stain behind and slightly above the eye.  

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Going into musth is a roving strategy primarily advantageous to old males not to young males

A seven-year study of Asian elephants from Nagarahole-Bandipur, a population centred around the Kabini region, yields interesting patterns of male elephant behaviour when in musth. Hormonal levels give musth males high energy and aggression levels and this state is often correlated with a propensity to mate. In two papers published in Journal of Mammology and Gajah, the team from Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, probes how this works in the Kabini population.

Elephants in musth

When an elephant is in a musth state, its urine shows increased testosterone levels. Also, temporin, a thick secretion, flows from the temporal ducts situated midway between their eyes and ears. Sometimes, the elephant dribbles urine as well. They hardly feed during musth and are more focussed on finding fertile females. They move from female to female, checking if she is fertile or not. Males enter into musth (show signs of musth) when there are in good body condition, and lost body condition over the time they are in musth because they are hardly feeding. Moreover, males can also mate when they are not in musth (they do not have to enter musth in order to mate). Therefore, people have been interested in finding out how exactly musth helps as a reproductive strategy since it is a very expensive strategy.

One way in which musth might give an advantage is that it might help to break a "queue" so to say of which male elephant is allowed to mate. It is also possible that musth allows for males to have greater energy and to rove (roam) over larger areas, which then gives males the opportunity to sample more females than nonmusth males.

Data were collected by a seven-member team. The team members drove along pre-selected routes for nearly 12 hours starting early morning and took photos and videos whenever they sighted elephants on these paths. “We aged all the elephants based on relative height, and ratio of head size to body size, and identified all the individuals based on ear, back and tail characteristics since we have a database based on long-term monitoring,” says P. Keerthipriya, a research associate at the Evolutionary and Integrative Biology Unit, JNCASR. Which individual male whether in musth or not was associated with which female was recorded.

No apparent advantage

The key findings of the group are that young (15-30 years old) males in musth did not have an advantage over older (over 30 years) non-musth males in terms of access to females. Old musth males had an advantage over old non-musth males, and also showed a roving strategy which allows for searching for multiple females. Therefore, musth seems to be a roving strategy that is primarily advantageous to old males and not to young males.

They also found that Kabini has a lower proportion of musth sightings compared to earlier studies from Kaziranga and Mudumalai. “Kabini has fewer males in the over-45 age class than Kaziranga and Mudumalai…. Hence the number of males of the 45 plus age-class seems to influence the occurrence of musth,” says Dr. Keerthipriya.

Female elephants have a four-month oestrous cycle in which they are ovulating for three or four days only. Thus, for a male to find an ovulating female and mate with her is, even normally, a rare occurrence. Further, if the female should get pregnant, she is out of circulation for about five years, because the pregnancy lasts two years and then she is lactating for over two-and-half years. Therefore, females are a rare resource for males seeking to produce offspring. Therefore, male mating strategies become very important in such a species.

Competing males

In this context, the obvious feature is the high degree of competition that exists among males to select and mate with the few available females. This study analyses how musth might affect this competition.

“The young males probably have to wait it out and invest in growth rather than reproduction while the competition is mostly among the old males,” says T.N.C. Vidya of the Evolutionary and Integrative Biology Unit, JNCASR, under whose leadership the work was done. “The low occurrence of musth in Kabini brings up interesting questions about how paternity will be distributed among males in Kabini, which is now being studied,” says Dr Vidya.

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Printable version | Jan 24, 2020 8:10:09 AM | https://www.thehindu.com/sci-tech/science/musth-does-not-necessarily-give-younger-male-asian-elephants-an-edge/article30420272.ece

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