Feature articles

Rats may be disgusting, but it’s people who have made the world they thrive in

posted Mar 3, 2015, 11:06 PM by Unknown user

by Steven Belmain

Rats are once again in the news, thanks to recent research, showing that the black death in medieval Europe may have been carried by gerbils rather than black rats.

Another study has indicated that farming expansion in east Africa is attracting plague-carrying rats and increasing the risk of transmission to humans.

These new findings on the role of rodents in the transmission of plague in Europe and Africa highlight some of the serious problems rodents can cause for people. Indeed, the impact of the plague on human civilisation makes it the single most important human disease in history, transforming the economy of medieval Europe through influencing social relations, culture, religion and politics.

Some have argued the effects of the black death helped “reset” European civilisation and contributed to the subsequent Renaissance and European expansionism in later centuries.

Read the rest of the article published by The Guardian, here.

Thai partners undergo workshop on rodent management and damage assessment

posted Aug 27, 2014, 7:14 PM by Unknown user   [ updated Sep 7, 2014, 7:01 PM by Gerardo Tomasito Laviña ‎(IRRI)‎ ]

Rodent damage during postharvest storage was one of the problems mentioned by Thai farmers when scientists from the Closing Rice Yield Gaps in Asia with Reduced Environmental Footprint (CORIGAP) assessed their needs in May 2013. In December 2013, rat and mouse problems were widely reported by farmers, with damage to seedlings in one of the farmers’ fields in Nong Jik Ree Village, one of CORIGAP’s project sites. In other regions of Thailand, reports of rodent damage to rice have been increasing over the last few years, with outbreaks of rodent population recently reported in Central Thailand.

To strengthen the knowledge and capacity of rice researchers in Thailand, 38 staff members from the Thai Rice Department attended a workshop on rodent management and damage assessment on 31 March-01 April 2014 at the Chainat Rice Research Center in Chainat Province. Read more

Report on a "ratada" occurring in 2011 in western Argentina

posted Jul 20, 2011, 6:24 PM by IRRC Coordination Unit   [ updated Sep 7, 2014, 7:30 PM by Gerardo Tomasito Laviña ‎(IRRI)‎ ]

In western Argentina, the bamboo, Chusquea culeou, flowered massively last spring (October-November, 2010), from San Carlos de Bariloche to Lago Puelo (41.3° to 42.2°S). It also flowered in a separate area further to the south in the Aysen-Coihaique area of Chile (≈45°S). The bamboo is the dominant understory plant on the Península Llao Llao (25 km W of San Carlos de Bariloche) (see photos at link 1 below), where the Valdivian rainforest is well developed and close to suburban and tourist housing. The superabundance of the bamboo seed, which started falling in January (2011), prolonged the breeding season of the "Colilargo" mouse (Oligoryzomys longicaudatus) (see the calphotos links in 2 below) into late winter. The number of these mice is now very high, and is a major public health concern. This mouse is the natural host of the Andes hantavirus, and causes a serious disease (HPS - hantavirus pulmonary syndrome) in humans that become infected (see links and publications in 1 below).

To the south of Bariloche, in the Río Manso area, mice left the forest in large numbers (the’exodus’ phase) and invaded barns and houses (see Picasa link in 3 below) during June and July, and there are cases of HPS in the infested areas at Aysen, Chile. Although their numbers ‘crashed’ at the beginning of August, the newspapers and television stations reported on the exodus event (see links in 4 below) when they were still so abundant. To the west of Bariloche the exodus phase began at the beginning of August in the area from Lago Frías (Argentina) to Lago Todos Los Santos (Chile). At Puerto Blest, only 5 km from Lago Frías the mice were still in the forest at the beginning of August, but at the end of the second week of August they began to leave the forest in high numbers. The differences in the beginnings of the exodus phase over such a short distance (i.e., between Lago Frías and Puerto Blest) is surprising.

At the beginning of the second week of September, in the Bariloche area the mice are still in the forests and the public is still focused (for now) on the catastrophe that the eruption of the Puyehue Volcano caused to the tourist business. It erupted on the 4-5th of June, 2011, and spewed out large, sand-grain sized ash during the first 24 hours. Since then the volcano continues to fume and send out much smaller, and more irritating dust particles. In the initial fall, about 2 cm of ash covered the forest floor at Llao Llao (see pictures in link 1 below). This small amount of ash did not have a negative effect on the mouse populations, as there were pregnant mice as late as the third week in August, and these females must have ovulated and implanted well after the ash fall. The delay in the ‘exodus’ phase near Bariloche may be because this area is at a higher elevation, and with colder temperatures than the localities further to the south and west, and so it is a bit ‘behind’ in the sequence. When the mice ‘swarm’ out of the forests and into the adjacent suburban areas and lakes (see pictures in link 2 below) then the photogenic aspect of “hordes of mice“ in the news will cause further difficulties for the tourist industry that is at the heart of the Bariloche economy.

  1. For continuing information on the bamboo flowering, the associated rodent outbreak near Bariloche, pictures and videos of the animals, and literature visit: https://sites.google.com/site/floracioncania/
  2. Photos of the “Colilargo” mouse, and their high numbers during a previous flowering to the north of Bariloche at: 
  3. Videos and photos of “hordes of Colilargo mice” at: https://picasaweb.google.com/113518369341044306238/RatadaRioMansoInferior?authuser=0&authkey=Gv1sRgCO2Z276iyLyWcg&feat=directlink
  4. Newspaper and television accounts of the ‘ratada’ and HPS at:

Pacific Rat

posted May 3, 2011, 7:26 PM by IRRC Coordination Unit   [ updated Sep 7, 2014, 6:44 PM by Gerardo Tomasito Laviña ‎(IRRI)‎ ]

The Pacific Rat (Rattus exulans) is also known as the Kiore, or Polynesian or Maori Rat. It is not indigenous to Australia but has established populations in the wild on islands here and elsewhere in Asia and the South Pacific. It is closely associated with human settlement and is often accidentally transported to new areas by people.

New videos on rodent management

posted Mar 4, 2011, 12:36 AM by IRRC Coordination Unit   [ updated Sep 7, 2014, 6:45 PM by Gerardo Tomasito Laviña ‎(IRRI)‎ ]

Two new videos on ecologically based rodent management (EBRM) were produced by the Irrigated Rice Research Consortium. Of rice and rats: an introduction to ecologically based rodent management, features the impacts of rodents on people and rice crops, particularly in Southeast Asia. The concept of EBRM is explained, and effective community actions to control rice field rats are suggested. How to control rice field rats is geared more for training purposes, and explains the breeding dynamics of the rice field rat and its relation to the rice planting season. It introduces EBRM and highlights effective community actions to control rice field rats, such as the trap barrier system.

Check out our Videos section to view the videos.

Philippines: Hungry rats invade eight Davao villages

posted Feb 20, 2011, 5:38 PM by IRRC Coordination Unit   [ updated Sep 7, 2014, 7:22 PM by Gerardo Tomasito Laviña ‎(IRRI)‎ ]

DAVAO CITY, Philippines—Hungry rodents descended on at least eight outlying villages here and devoured hundreds of hectares of agricultural crops, including cassava, on which most indigenous people rely for their day to day survival, the city agriculture office reported Friday, February 18, 2011.

Leo Avila, head of the city’s agriculture office, said the infestation, which started at the height of the heavy rains that spawned flooding last month, has prompted the city council to declare a state of calamity in these villages in Paquibato district.

The initial damage report, Avila said, showed that the rats also gobbled up other crops such as corn, cacao, coffee and rice and damaged coconut trees.

He said the extent of the damage was still being ascertained as infestation continued in some areas. But as of this week, the rodents have already damaged some 1,391 hectares of crops.

Avila said the infested area was about 60 percent of the 2,330 total area devoted to agriculture in Paquibato district.

He said farmers dependent on cassava and other crops for their daily sustenance have moved to the city proper to find means of feeding their families.

Avila could not say, however, exactly how many of the estimated 4,000 affected families had evacuated due to lack of food.

“The aforementioned infestation brings restlessness and hopelessness to farmers, hence a lot of them decided to stay in the central areas of the city to ask for donations or perform unfamiliar chores, which will surely endanger their life considering they are not familiar with the city’s lifestyle,” a statement issued by village officials, said.

Avila said even before the village officials issued the statement, Mayor Sara Duterte had already asked the city council to declare Paquibato under the state of calamity.

He said the city social welfare office takes charge of delivering assistance to affected families while the city agriculture office has started taking measures to control the rodents.

Avila said among the moves they have taken is the use of poison and traps.

“We will do everything to help the farmers, since they rely so much on their crops,” Avila said.

Avila said they were still unsure about the upsurge in rat population in Paquibato but added that they suspected it had something to do with changes in the weather.

Richel Zamora, an agriculture technologist who surveyed the area, said even the locals were surprised by this occurrence.

“Rats are nocturnal and will start to hunt for food during night time. But (in Paquibato), even at daytime, the rats in great numbers are seen eating the crops,” Zamora said.

By Dennis Jay Santos
Reposted from Philippine Daily Inquirer Web site http://newsinfo.inquirer.net/breakingnews/regions/view/20110218-320964/Hungry-rats-invade-eight-Davao-viages


NEW BOOK! Rodent outbreaks: Ecology and impacts

posted Nov 17, 2010, 7:14 PM by IRRC Coordination Unit   [ updated Sep 7, 2014, 7:15 PM by Gerardo Tomasito Laviña ‎(IRRI)‎ ]

The impacts of rodents in both developing and developed countries are legendary. Myths and dogma about rodents and their outbreaks abound. They are imbedded in the culture and language of many societies. In many instances, it is the acceptance of these outbreaks by society that is our greatest challenge as crop protection specialists or conservation biologists. The reason these episodic outbreaks become etched in the socio-cultural psyche from the sparsely populated uplands of Laos to the considerably more affluent agricultural lands of Europe is that the impacts are often staggering—economically, socially, and even politically. This book is a collation of contributions from Asia, Africa, Oceania (Australia and New Zealand), Europe, and North America. The advent of ecologically based rodent management (EBRM) has stimulated the progress summarized in this book. The contributions provide a modern appraisal to an age-old problem through a better understanding of the mechanisms that lead to rodent outbreaks, why rodent population numbers increase under different circumstances, and the impact of outbreaks in a range of different agroecosystems and native forests in different parts of the world. This is an encouraging progress report driven by scientists passionate about rodents, about people, about conservation, and about improving our knowledge of these species and the ecosystems they inhabit. And, in a novel twist, there is an appendix of recipes for preparing rat meat. You will be more than tempted to try one of these dishes the next time you travel in Asia or Africa.

Edited by Grant Singleton, Steve Belmain, Peter Brown, Bill Hardy
Publisher: International Rice Research Institute
Los Baños, Philippines
Publication date: November 2010
Web availability: IRRI Google Books (http://books.irri.org/)

Click here to view the book online.
Rodent outbreaks and their impact on food security in Asia: an overview
GR Singleton, SR Belmain, PR Brown

Section 1 
Rodent outbreaks and bamboo flowering in Asia
Chronicle and impacts of the 2005-09 mautam in Mizoram
KP Aplin, J Lalsiamliana

The Chittagong story: studies on the ecology of rat floods and bamboo masting
SR Belmain, N Chakma, NJ Sarker, SU Sarker, SK Sarker, NQ Kamal

The Chittagong story: a regional damage assessment during a rodent population outbreak
SKM Ahaduzzaman, SK Sarker

Rodent population outbreaks associated with bamboo flowering in Chin State, Myanmar
NM Htwe, GR Singleton, AM Thwe, YY Lwin

Rodent outbreaks in the uplands of Lao PDR
B Douangboupha, GR Singleton, PR Brown, K Khamphoukeo

Section 2
Rodent impacts in lowland intensive rice systems in Southeast and South Asia
Rodent impacts in lowland irrigated intensive rice systems in West Java, Indonesia.
Sudarmaji, GR Singleton, PR Brown, J Jacob, N Herawati

Rodent outbreaks in South Sulawesi, Indonesia: the importance of understanding cultural norms
D Baco, R Nasruddin, H Juddawi

Rodent impacts in lowland irrigated intensive rice systems in Vietnam
HN Huan, VTQ Nga, PR Brown, MTM Phung, GR Singleton

Socio-cultural factors influencing adoption of ecologically based rodent pest management.
FG Palis, GR Singleton, PR Brown, NH Huan, NTD Nga

Response options to rodent outbreaks following extreme weather events: cyclone Nargis, a case study.
GR Singleton, NM Htwe, LA Hinds, W Soe

Analysis of communication pathways and impacts of the Boo! Boo! Rat! campaign
RJB Flor, GR Singleton

Section 3
Rodent outbreaks in other regions: a search for generalities
Rodent outbreaks in Europe: dynamics and damage
J Jacob, E Tkadlec

Rodent outbreaks in Australia: mouse plagues in cereal crops
PR Brown, GR Singleton, RP Pech, LA Hinds, CJ Krebs

Rodent outbreaks in New Zealand
WA Ruscoe, RP Pech

Rodent outbreaks in North America
G Witmer, G Proulx

Rodent outbreaks in sub-Saharan Africa
H Leirs, V Sluydts, R Makundi

Recipes for rodent culinary delights

Impacts of rodent outbreaks on food security in Asia

posted Sep 2, 2010, 2:00 AM by IRRC Coordination Unit   [ updated Sep 7, 2014, 7:03 PM by Gerardo Tomasito Laviña ‎(IRRI)‎ ]

Since 2007, a spate of rodent outbreaks has led to severe food shortages in Asia, affecting highly vulnerable and food-insecure families. Little has been documented about wildlife-management issues associated with these outbreaks. The aims of the present study were to synthesise what we know about rodent outbreaks in Asia, and identify important gaps in our knowledge. We compiled information from agencies of the United Nations, non-government organisations and the authors. The authors conducted site visits to areas affected by outbreaks of rodent populations, and convened an international conference in October 2009 to share knowledge. Bamboo masting is clearly implicated as the primary cause of the rodent population outbreaks that led to severe food shortages in Mizoram (India), Chin State (Myanmar), Chittagong Hill Tracts (Bangladesh) and upland provinces of Lao PDR. In Laos, emergency food assistance was required for 85 000–145 000 people. In 2009, high rodent losses occurred also in lowland irrigated rice-based systems in the Philippines, Myanmar and Indonesia, not related to bamboo masting. Asynchronous or aseasonal growing of rice crops was a common element in these outbreaks. In the Ayeyarwaddy delta, Myanmar, 2.6 million rats were collected in 3 months through community activities; this outbreak appeared to be related to an extreme climatic event, Cyclone Nargis. There are two key features of rodent outbreaks that makethe future uncertain. First, climate change and extreme climatic events will increase impacts of rodents on agricultural production. Second, there is food-security pressure in some countries to grow three crops per year. Increased cropping intensity will reduce fallow periods and create ideal conditions for rodents to breed nearly continuously. Implications of the research are as follows: (i) rodent outbreaks are a consequence of enhanced reproduction and natural mortality is of minor importance, particularly with rapidly increasing populations; therefore, we need to focus more on methods for disrupting reproduction; (ii) a stronger understanding of the ecology of pest species and community dynamics will enable ecologically sustainable management; (iii) we need landscape approaches that focus on crop synchrony, and timely coordinated community action to manage pest species and conserve desirable species; and (iv) a simple monitoring system can help implement ecologically based rodent management.

Citation: Singleton GR, Belmain S, Brown PR, Aplin K, Nyo Me Htwe. 2010. Impacts of rodent outbreaks on food security in Asia. Wildlife Research 37:355-359.

Holding back a torrent of rats

posted Oct 19, 2009, 10:41 PM by IRRC Coordination Unit   [ updated Sep 7, 2014, 7:11 PM by Gerardo Tomasito Laviña ‎(IRRI)‎ ]

A “rat flood.” That's what the tribes in Bangladesh's Chittagong Hill Tracts call it. Every 48 years, the bamboo forests that dominate the uplands of Bangladesh, Northeast India, and Myanmar (formerly known as Burma) simultaneously produce a feast of pear-sized fruit that allows rat populations to explode. After consuming the fruit, the rodents attack nearby fields, devouring 50% to 100% of the rice crop. Rat floods caused famine in 1863, 1911, and 1959, when the misery touched off a rebellion in what is now India’s Mizoram State.

Rat floods may be unusual, but rodent losses are a perennial problem worldwide. In Asia, for instance, rodents devour an estimated 6% of the annual rice harvest—roughly enough to feed Indonesia’s 240 million people for a year. And they do damage in nearly every phase of farming, from munching on seedlings to eating stored grain.

Many farmers and agricultural officials, however, shrug. “Philippines farmers say, ‘For every 10 rows of rice we plant, seven are for the family, two for the rats, and one for the birds,’” says Grant Singleton, a wildlife ecologist at the International Rice Research Institute in Los Baños, Philippines. Rat fatalism runs so deep that agricultural universities, which have courses in insect management, offer no training in defending against rodents. Thanks in part to growing concerns about food security, however, Singleton says rats are now “getting on the radar.”

Rat race

In the wake of that recognition, agriculture agencies across Asia have started spreading the word about some relatively simple rat countermeasures. Small-scale farmers, for instance, often store grain in open bins in their homes and “don’t appreciate what [rats] are taking,” says Singleton. Steps such as raising the bin off the floor and installing metal flashing around bin legs can cut losses.

Rat fighters are also urging all farmers within a community to plant their crops within 2 weeks of each other. If fields ripen together, grain is available for a shorter time and rodents curtail breeding. Communities can also maximize efforts to flush out, trap, and kill rats by launching campaigns before planting begins. When paddies and fields are fallow, rodents tend to congregate in the thickets between fields and along roads and irrigation channels. “While they are aggregated, they are much easier to control,” says Singleton. Most important, he says, communities need to work together: “If you do everything we think should be done to manage rodents and your neighbor does not, you will inherit those rodents.”

Some of the 200-plus species of rats that pester farmers, however, require carefully timed control strategies that reflect unique habits. For instance, Indonesia’s rice field rat, Rattus argentiventer, does its worst damage just as grains start to form, because the rats must eat huge quantities of immature grain to get sufficient nutrition; as the grain ripens, they eat less. In contrast, Myanmar’s Bandicota bengalensis rats cause little damage until just before harvest, when they grab all the grain they can to horde in burrows. “The dynamics of the damage differs by species,” Singleton says.

Rodents also respond to unusual patterns of food availability. In May 2008, Cyclone Nargis devastated the rice crop in Myanmar’s Ayeyarwady delta (Science, 8 May 2009, p. 715). To recover, farmers planted rice when and where they could. As a result, the rice ripened at different times in neighboring paddies—providing a steady food supply for rats. The rodents bred for longer than usual, leading to a surprise outbreak this year that further dented precarious food supplies.

All together now

Even recognized events such as bamboo fruiting, however, can be difficult to prepare for. One problem is that agricultural agencies are reluctant to fund the long-term studies needed to understand the connection between bamboo “masting,” where an entire population produces fruit simultaneously, and rodent explosions. Masting can occur at intervals ranging from several years to more than 100 years, depending on the species, so “there are few opportunities to study this,” says Steven Belmain, an ecologist at the Natural Resources Institute of the University of Greenwich in Chatham Maritime, U.K. Only over the last several years, for instance, have scientists unraveled what happens to rat populations when masting occurs in Melocanna baccifera, which makes up more than 80% of the bamboo in Bangladesh, India’s Mizoram State, and Myanmar.

Typically, rodents in that region start breeding in April or May, after the dry season when the first monsoon rains allow food in the form of insects and plants to proliferate. Upland farmers plant their rain-fed crops at the same time. Rodent populations build through the summer and damage the harvest, but losses are usually manageable. Once every 48 years, however, the Melocanna bamboo starts dropping fruit in February. With food abundant, the rodents start breeding 2 to 3 months earlier than usual. This head start means that “multiple generations of rats are breeding, [producing] exponential growth in the population,” says Ken Aplin, a wildlife biologist at Australia’s Commonwealth Scientific and Industrial Research Organisation in Canberra. By autumn, just as crops are ripening, the food in the bamboo forest is gone, leading to “a mass movement [of rodents] from the forest into the fields,” says Aplin, who advised the Mizoram state government on dealing with masting. But “there is no way to stop the ecological phenomenon,” says Belmain. “You can only manage the damage.”

Anticipating the 2008 Melocanna masting event, for instance, the Mizoram government launched the 5-year Bamboo Flowering and Famine Combat Scheme that included upgrading roads to carry aid to remote communities, rat-proofing warehouses, and encouraging farmers to plant early-yield rice varieties and alternative crops less attractive to rodents. When the inevitable rat flood hit, the government and relief organizations provided food assistance. “In a broad sense, it worked,” says Aplin, though it will take several years for the area to completely recover.

Now, researchers are pondering how the lessons learned could help other regions. If researchers can pin down when and where masting events will occur, “it might allow us to understand which communities will be hit so limited resources can be better targeted,” says Belmain. Rat flood control, it seems, is just getting started.

–DENNIS NORMILE, Science, Vol. 327, 12 February 2010, www.sciencemag.org

Click below to download the full pdf

Rodent management training in Mt. Province, Philippines

posted Oct 19, 2009, 9:47 PM by IRRC Coordination Unit   [ updated Sep 7, 2014, 7:04 PM by Gerardo Tomasito Laviña ‎(IRRI)‎ ]

The Irrigated Rice Research Consortium (IRRC) held a training course on ecologically based rodent management on 27-28 May at Barangay Belwang, Mountain Province, Philippines.

The training course was co-organized by the Social Action Development Center (SADC) Vicariate of Bontoc-Lagawe, Mountain Province.

Belwang, a remote mountain village in the Cordillera Administrative Region, is currently experiencing serious rodent problems in their rice terraces and fruit orchards. With the help of Rolf Boller, project leader of the Environment and Sustainable Agriculture Program of SADC, and the Office of the Provincial Agriculturist in Mountain Province, the community sought assistance from rodent ecology expert and IRRC coordinator Grant Singleton.

The course started with a demonstration on how to set up rat traps in the rice terraces, fruit orchards, and village. The formal training on the second day was attended by 115 farmers, who constructed a cropping calendar and identified rice as their dominant crop. They identified rats as the most important factor limiting their rice production. Individual farmers indicated 10-50% losses in harvest potential of rice because of rats.

A lecture was given on the biology of the local rodent population, followed by a detailed decision analysis of the community’s current rat-trapping methods. The participants were introduced to the benefits of synchronous cropping, good hygiene in the fields and houses, community action, and the community trap barrier system. The final part of the formal training included a workshop with 10 key farmers to formulate an action plan.

The IRRC team was composed of Dr. Singleton, PhD scholar Nyo Me Htwe, wildlife biologists Harvey Garcia and Vincent Sluydts, and communication officer Rona Rojas.

By Rona Niña Mae Rojas

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