Rat Outbreaks that Occur Every 48 Years
Once every 48 years, bamboo forests in parts of northeast India go into
To help control rodent outbreaks, the Mizoram government pays farmers two rupees (about two cents) for every rat they kill. Here, two scientists examine a pile of 30,000 rat tails.
Then, like clockwork, the flowering is invariably
followed by a plague of black rats that appear to spring from nowhere to
spread destruction and famine in their wake.
For the first time on
film, NOVA and National Geographic capture this rat population explosion
in vivid detail and show how scientists are unraveling the connections
between bamboo flowering and rat outbreaks.
Ultimately, their research
should help local people better cope with the next attack—due in 2056.
The black rat originated in India and Southeast Asia, and spread to the Near East and Egypt, and then throughout the Roman Empire, reaching England as early as the 1st century. Europeans subsequently spread it throughout the world.
The black rat is, again largely confined to warmer areas, having been supplanted by the brown rat (Rattus norvegicus) in cooler regions and urban areas.
In addition to being larger and more aggressive, the change from wooden structures and thatched roofs to bricked and tiled buildings favored the burrowing brown rats over the arboreal black rats.
In addition, brown rats eat a wider variety of foods, and are more resistant to weather extremes.
Black rat populations can explode under certain circumstances, perhaps having to do with the timing of the fruiting of the bamboo plant, and cause devastation to the plantings of subsistence farmers; this phenomenon, Mautam, is happening currently in parts of India.
Black rats are thought to have arrived in Australia with the First Fleet, and subsequently spread to many coastal regions in the country.
In New Zealand, black rats have an unusual distribution and importance, in that they are utterly pervasive through native forests, scrublands, and urban parklands. This is typical only of oceanic islands that lack native mammals, especially other rodents.
Throughout most of the world, black rats are found only in disturbed habitats near people, mainly near the coast. Black rats are the most frequent predator of small forest birds, invertebrates, and perhaps lizards in New Zealand forests, and are key ecosystem changers. Controlling their abundance on usefully large areas of the New Zealand mainland is a crucial current challenge for conservation managers.
Black rats adapt to a wide range of habitats. In urban areas they are found around warehouses residential, buildings, and other human settlements.
They are also found in agricultural areas, such as in barns and crop fields. In urban areas they prefer to live in dry upper levels of buildings, so they are commonly found in wall cavities and false ceilings.
In the wild, black rats live in cliffs, rocks, the ground, and trees.
They are great climbers and prefer to live in trees, such as pines and palm trees. Their nests are typically spherical and made of shredded material, including sticks, leaves, other vegetation, and cloth. In the absence of trees, they can burrow into the ground.
Black rats are also found around fences, ponds, riverbanks, streams, and reservoirs.
The black rat, along with the brown rat, is one of the most widespread rats and animal species in the world.