The black rat (Rattus rattus) causes severe damage to coconut (Cocos nucifera) crops in Colombia. These rodents climb to the crown of producing palms and often nest there. Damage results from the rats gnawing the shells of the coconuts until they penetrate to the endosperm; the perforated nuts will fall within a period of 15 days and are unsuitable for harvest. Since 1972, the Colombian Agricultural Research Institute (Instituto Colombiano Agropecuario or ICA), through its Vertebrate Control Program, has been conducting a series of investigations to obtain information about the characteristics of this damage and the best means of reducing it. Damage surveys in several of the principal coconut-producing areas reveal a high percentage of crop loss (e.g., Tumlaco - 20%, San Andres Island - 34%, and Gorgona Island - 60%) and illustrate the seriousness of the problem. The lack of water (i.e., rainfall) during the dry season seems to be associated with increased damage. In some areas, such as San Andres, the planting density is excessively high. Hence, physical barriers such as metal bands on the trunk are ineffective -- the proximity of the palms allows the rats to transit easily among adjacent trees on overlapping fronds. Our observations indicate that chemical control using anticoagulant baits placed in the palm crowns, significantly reduces damage. The effect of a single baiting can last up to six months, with the length of the effect dependent upon cultural practices implemented after treatment (e.g., maintaining cleanliness of area, weed control, etc.). At present, chemical control and associated cultural practices is the program recommended by ICA for reduction of rat damage to coconut crops in Colombia.

The tropical zones of Latin America are sources of a great faunal richness. A significant number of mammals are associated with damage to the agricultural and livestock industries of Colombia. Some studies have indicated that rodents cause serious economic and social damage in the agricultural, livestock, and stored product sectors of the Colombian economy. Evaluations of this damage have been based on three criteria: 1) the characteristics of the damage; 2) the species of rodent involved; and 3) the loss of production at harvest. Cereals and oil-producing crops are most affected as standing crops; in the livestock area, poultry and pork production are most affected; many agricultural products, especially grains, are attacked by rodents during the post-harvest stage. The level of economic loss caused by rodents can range from about 4% to about 50% depending on the crop, the season, and the species of rodent involved in the damage. Social damages are characterized by the transmission of illnesses such as salmonellosis and leptospirosis via contaminated foods or grains. Six species of rodents of the families Cricetidae and Muridae are most commonly associated with these problems in Colombia.