Every 40 to 50 years, the bamboo Melocanna baccifera blooms in Mizoram, an Indian state between Bangladesh and Myanmar Burma. The bamboo covers one third of the state of the folded and hilly region. The rizomes hold together the soil of the slopes of the hills.
The stems, leaves, buds, fruits and seeds of the bamboo are crucial to the livelihood of most of the inhabitants of the country. The ripening of the fruits of the bamboo starts an ecological cascade of events that have dire consequences for the local population. The last one in the twentieth century was in 1959 to 1961. That bloom and the precedent ones in the historical record spurred a plague of rats feeding off the bamboo’s fruit. The population of stinkbug (a hemipterous known as thangnang in Mizo) is also known to explode in size. The rats eat up off the crops before the harvest, sending the population into misery and famine.
Ecology of the black rat in the bamboo forests
The black rat usually represents only 10% of all the rats of all species in the bamboo forests in normal years. In Mautam years, the black rats make up more than 90% of the total culled rodents. The success of the black rat is due to its larger litters and shorter pregnancy. The larger litters are controlled by mothers eating newly born rats in normal years. Their pregnancies are 5 days shorter than other species. This makes this species profit the most from the abundance of seeds in Mautam years.
The same female rat may lay one litter every month during the Mautam. Most female rats reproduce at the same time. As a consequence, the population grows in pulses. From 50, they grow to 200, then 600, etc. Eventually the seeds of bamboo ran out and the rats invade the nearby fields. If the crop is not yet harvested, the rats will eat all the grains of rice and maize.
The gregarious synchronisation of the flowering of bamboo has a period of approximately 40-50 years depending on the species. It marks the death of the plants in thousands of square kilometres around and the sprout of the next generation. The flowering is controlled by the genome; if the bamboo is cut before it flowers, if will do so immediately upon its regrowth.
This cycle is longer than the emergence of the cicadas in North West America every 17 years. Phyllostachys bambusoides flowers every 130 years in China. Which type of parasite or predator might have tuned the biological clock of the bamboo? And why is the rat and another insect the only ones who benefit from this cyclical bloom?
The bamboo flowering changed the regime of Mizoram
The Mautam outbreaks shape up the politics of the state too. The growth of the number of rats captured before 1959 made the Mizo people warn of the imminent Mautam. These calls were dismissed as folk superstition by the Indian Government of Assam, the state whose one of its districts were Mizoram. The officials failed to prepare for the famine that followed. This lead to the foundation of the Mizo National Famine Front to provide relief to the famine. It later became the Mizo National Front (MNF), which staged a major uprising in 1966. MNF fought a separatist war against the Indian Army. In 1986 Mizoram was granted autonomy as a separate state from India and Assam.
The influence of ecology in our civilization is still largely unknown at best, underestimated or overlooked more often than not. Some scientists of the Earth Institute at Columbia University studied 175 countries and 234 conflicts that killed more than 25 people killed in a given year. They found a strong correlation between the occurrence of el Niño events with upsprings and civil wars in countries. From 1950 to 2004 the chance of civil war breaking out was about 3 percent during La Niña; during El Niño, the chance doubled, to 6 percent. Countries not affected by the El Niño-Southern Oscillation remained at 2 percent no matter what. Overall, the scientists calculated that El Niño may have played a role in 21 percent of civil wars worldwide—and nearly 30 percent in those countries affected by El Niño.
How to prevent famine and wars from the Mautam
Areas only 5 to 10 km away can be affected very differently be the pest, either by different progress of the flowering waves of the bamboos, agricultural practices or other factors. There are around 30 bamboo species growing in the Bengal Bay region. Their ecology is still largely unknown.
It is unclear yet how to effectively resist the rodents floods. The locals slash and burn vegetation to grow vegetables, a practice known as jhum cultivation. The government of Mizoram has launched a policy to end Jhum cultivation.
If you want to see some of the action of the last Mautam watch Rat Attack! The documentary has the typically freak title of all the productions of National Geographic. Shot in of 2009, the video is a chronicle of the research of Ken Applin, a rodent expert, in Mizoram in 2007.