Rat Attack

TV Program Description
Original PBS Broadcast Date: February 24, 2009

Once every 48 years, forests of the bamboo known as Melocanna baccifera go into exuberant flower in parts of northeast India. And then, like clockwork, the event is invariably followed by a plague of black rats that spring from nowhere to spread destruction and famine in their wake. For the first time on film, NOVA and National Geographic capture this massive rat population explosion in the kind of vivid detail not possible in 1959, when the last invasion occurred.

Shot in the Indian state of Mizoram, where the massive onslaught occurred on schedule in 2008, this NOVA/National Geographic Televison special shows hordes of rats emerging from the forest right at harvest season, consuming entire crops and leaving subsistence farmers facing starvation. The chance to document and study this remarkable rat outbreak won't occur again for another half-century. (By contrast, oak-tree masting, the best-studied mass seeding in the world, occurs every few years—see Population Explosion.)

In the film, the world's foremost rat biologist, Ken Aplin of the Australian National Wildlife Collection (and National Geographic research grantee) arrives before the onset of the attack to try to understand the cause of the colossal infestation, which is steeped in local lore. According to tradition, the regular 48-year cycle of bamboo flowering, seeding, and death, called Mautam, spawns armies of rats, which come out of trees and underground burrows to indulge in the abundance of food. (Noted ecologist Dan Janzen explains why this happens, and what's in the relationship for all involved—plants, animals, and people.)

Aplin, who has been studying rats for 10 years, has been bitten countless times but has no fear of the rodents, just sheer enthusiasm. In the film, he is literally up to his elbows in rats, reaching into burrows to pull out litters of rat pups while looking for clues as to how the invasion is progressing. "A lot of people are disgusted by rats," Aplin tells NOVA, "but I love rats. They're so successful!"

Once the invasion starts to wane as both natural and human-produced foods begin running out, the now-starving rats begin killing their own infants in order to survive. (See Killer Instinct for a look at possible reasons why animals commit infanticide, which is surprisingly widespread in nature.)

Also featured in the program is James Lalsiamliana, a biologist with the Mizoram Agriculture Department, who teams up with Aplin to solve the rodent mystery. At one point they inspect a pile of 30,000 rat tails collected in a government-sponsored bounty program designed to reduce the invaders' numbers. The impressive mound of tails is a small fraction of the over 1.5 million rat tails collected in the region. But this substantial culling appears to have had little effect on the burgeoning rat population.

So prolific are the creatures that local people regard the bamboo seeds on which they feed as a powerful aphrodisiac—a theory tested by Mizoram residents in many home kitchens, where they concoct delicacies with the seeds. NOVA also shows how some of the local Mizo people eat the rats themselves for food. (So does Jeremy Zipple, the coproducer who doesn't shy away from the full experience of living among the Mizo people during the film shoot—see The Producer's Story.)

"Rat Attack" sheds light on the amazing biology of the black rat (Rattus rattus) and its relationship with the life cycle of the Melocanna bamboo, which has a remarkable biology of its own. Given the long interval between rat plagues, Aplin says this is his last chance to work out what really happens during Mautam, to work out the details of the connection between bamboo flowering and rat outbreaks. And, ultimately, to help local people better cope with the next attack—due in 2056.

Program Transcript
Program Credits

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Rat Attack

A black rat can gnaw through the large seed of the Melocanna bamboo (above). This ability ensures that, when the bamboo puts out its massive seed crop every half-century, the native wild rat population will follow suit, reproducing at such a high rate that a plague of rats quickly ensues, with devastating effects on nearby farm fields.

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© | Created February 2009