Unwanted and unintended effects of culling: A case for ecologically‐based rodent management

Abstract

In this study, the ecological effects of culling programs are considered in the context of rodent pest management. Despite the escalation of rodent problems globally, over the past quarter of a century there have not been many new developments in culling programs directed at managing these populations. There is a strong reliance on broad scale use of chemical rodenticides or other lethal methods of control. The ecological consequences of culling programs based on chemical rodenticides and bounty systems are considered. Although rodents cause tremendous economic hardship to people on a continental scale, usually less than 10% of species cause substantial impacts. Indeed, many species of rodent provide important "ecological services" and, given that culling programs rarely distinguish between rodent species, often the non-pest rodents are at grave risk. Rodent control is conducted with little appreciation of what proportion of the population would need to be culled for a significant reduction in economic damage. In Indonesian rice fields, once rodent densities are high then a reduction in yield loss from 30% to 15% would require more than 75% of the population to be culled; a reduction to less than 5% yield loss would require more than a 95% cull. The negative ecological consequences of culling can be better managed if the method is specifically tailored to the species that need to be managed. A greater emphasis on ecologically-based rodent management would assist markedly in reducing the unwanted and unintended effects of culling.

Global parasite and Rattus rodent invasions: The consequences for rodent‐borne diseases

“…It is well known that once introduced, all these species can strongly interact with indigenous fauna and flora, and can alter the colonized ecosystems in different ways (Courchamp et al 2003;Banks & Hughes 2012) and can also have economic impacts. Moreover these species display sufficient ecological differences that they would be expected to interact differently with local small mammal communities (Courchamp et al 2003, Singleton et al 2007). All these Rattus species have radically and explosively expanded their geographic range as a consequence of human activities.…”

Is quantity or quality of food influencing the reproduction of rice-field rats in the Philippines?

“…Myanmar; Htwe et al 2013) or changing agricultural practices (e.g. Myanmar, Vietnam; Singleton et al 2007Singleton et al , 2010. Asynchronous or aseasonal planting of rice can provide high-quality food for rodents for longer periods of time per year and extend their breeding season.…”

Survival and recruitment of the multimammate mouse, Mastomys natalensis (Smith 1834), in a rice agro-ecosystem

“…Farmers in the study area reported that 53% of farmers control rodent pests using rodenticides, and 47% use physical control, e.g., pitfall traps, kill traps, but it is not known whether these efforts have had any marked impact on rodent population dynamics during our study. As most rodent management tends to be ad hoc and uncoordinated ( Singleton et al 2007 ), we can argue that the rodent management by farmers has probably had little impact on our observations of survival and recruitment.…”