Rodent Control Problems in Developing Countries

None of the so-called developing countries has an adequate rodent control program at present. In only a few of these countries is any rodent control research occurring despite the fact that rodent problems are actually quite serious in many regions and potentially so in others. Expertise, techniques and materials from the developed countries are of limited usefulness because of major differences in rodent species involved, standards for food handling and sanitation, and in the cultural contexts in which rodent control must occur. Trained personnel, both for control work and the basic research needed, are in very short supply. In addition, rodent control is frequently a low priority item in the generally meager budgets of developing countries. To date international agencies, foreign a i d programs and foundations have had very limited success in altering this situation, although at present there is an upsurge of interest in rodent control problems. The problems of rodent control are much the same in both the developing and the developed countries. The major difference is that these problems are far more serious, widespread and difficult to solve in the developing countries. Thus, it is more a question of degree than of kind. Even the problems arising from reluctance to k i l l rats because of religious beliefs in Asia have somewhat of a counterpart in laws preventing cruelty to animals in North America and Europe. This does not mean, however, that knowledge and techniques available in the developed countries are easily applicable in developing countries. Such a view ignores the profound technical, cultural and political differences not only between the two groups of nations but also among the developing countries themselves. Among the technical problems the most serious is that the rodents themselves are very poorly known. Basic life history studies are badly needed throughout Asia, Africa and the Americas. In some regions, India and Pakistan, for example, much has already been published but it is largely anecdotal and f a i l s to include work on population dynamics. There has, of course, been some research on the taxonomy of rodents in developing countries. But, even here, the murid rodents, which include a major share of pest species are a taxonomically difficult group and more work is needed. One of the few major research efforts on the population dynamics of a pest rodent is the study on the Lesser Bandicoot Rat (Bandicota bengalensis) in Calcutta warehouses by Spille tt (1968). He was able to demonstrate in this species one of the highest population densities and reproductive performances yet reported under natural conditions. His estimates on food losses, based on known intake and population density, are of considerable value in assessing the impact of this species on man. This problem of assessing damage is an important one throughout the developing countries. In India estimates of rodent damage to foodstuffs range from 2.4 m i l l i o n to 26 m i l l i o n tons annually (Pingale et al., 1967). When such estimates can range over an entire order of magnitude, there is clearly room for improvement. The chief difficulty lies in the extrapolation of very local and l i m i t e d studies to very large regions, which magnifies any errors. The truth is, no one knows what food and goods losses from rodents are in the developing countries, or, for that matter, anywhere else. Fortunately, there is presently a U.S. A I D rodent research team in the Philippines working on rat damage to rice. Equivalent work on other food crops is not under way. Rat problems are aggravated by the fact that most of the species involved are native to the developing countries and are abundant and well-adapted to these areas. For example, the skin collections in East African universities contain a bewildering variety of rat and mouse species, many of them already serious pests and many more of them potential pests to developing agricultural regions. In India and Pakistan over 14 species are serious pests (Bentley, 1968; Pingale et al., op. cit.). Particularly in Asia, agriculture is very ancient and rodents have had a long time to adapt to human-dominated environments. This raises the question of the occasional c a l ls for rodent "eradication." It is very doubtful that we could successfully eliminate a l l the pest rodents from regions as complex as those in the tropics and subtropics. Even if th is were possible, our current lack of understanding of the other roles played by rodents in their ecosystems rules out such drastic measures. Rodents may consume insects, weed seeds and a variety of other items which are important to man's agriculture and public health.