The interplay of rodent behaviour and semiochemistry: from scientific principles to control strategies

Commensal rodents are major pests of humankind. They have profoundly negative impacts through crop and food damage, carry human and animal diseases, cause allergy and asthma, and damage to the built environment. The costs of rodent infestations are difficult to quantify, but worldwide this runs to many billions of pounds. For example, food loss and damage caused by rats in the United States alone was estimated as $19 billion in 2000. In rice-growing regions, rodents cause annual pre-harvest losses of 5-17%: models suggest that a 5% reduction in rodent losses to the cereal harvest in undernourished countries could feed one third of all undernourished people worldwide. In the built environment, cable damage presents a significant risk of fire and electrocution, with costs of damage to infrastructure in the UK estimated around £200 million (2004). Rodents are also important in the spread of a large number of livestock and human diseases, including foodborne diseases; and contribute a significant source of allergens in residential areas that correlate with asthmatic symptoms. Current control strategies rely heavily on widespread and rather indiscriminate use of rodenticides, although the need for more integrated pest management approaches is increasingly recognized. Anticoagulant rodenticides (at least 90% of those used within Europe) are coming under increasing regulatory pressures due to persistence in the environment and negative impact on non-target species. There are growing problems of rodenticide resistance and public concern about humaneness. Thus, there are urgent needs to develop new control approaches, to significantly increase the efficiency and targeting of conventional approaches, and to develop alternative non-lethal approaches that increase the effectiveness, sustainability and humaneness of rodent control. Our goal is to develop new tools and strategies for rodent pest control, based on the use of scent signals (semiochemicals) to manipulate rodent behaviour. Rodents are critically dependent on scent cues for social communication, for the coordination of reproduction and reproductive investment, for navigation around the habitat and for predator avoidance. This provides the opportunity to manipulate such signals for control purposes, as has been developed very successfully for insect pest control. However, the complexity and individual variability of mammalian scent cues, combined with flexible and adaptive responses, demands a subtle integrated and interdisciplinary approach to understand the key components of signal and response and establish the potential for manipulation from a practical perspective. To achieve this, we bring together world-leading experts in wild rodent behaviour and chemical communication, the chemistry of volatile and protein pheromones, and the deployment of semiochemical-mediated strategies for pest control. The programme will focus on house mice and brown rats as the two most important rodent pests in the UK and worldwide, and will generate approaches that can also be translated to other rodent pest species. Our specific objectives are to * build a full understanding of the scent components that stimulate behaviours that have considerable potential for pest control; * understand scent deposits and signals and how these change with scent age, so that we can mimic them for pest control and use them to monitor infestations; * explore how to exploit the flexible learning that is typical of mammalian responses to scents; * test the ability of synthetic signals to manipulate key aspects of behaviour and reproduction in semi-natural environments. A stakeholder group comprising representatives of the pest control, environmental health and food industries, regulatory bodies, and scientific expertise of rodent pests in developing countries will ensure appropriate focus and provide pathways to the industries involved for subsequent deployment.

Our goal is to develop new tools and strategies for rodent pest control, based on the use of scent signals (semiochemicals) to manipulate rodent behaviour. Rodents are critically dependent on scent communication to coordinate reproductive behaviour and investment, competitive and cooperative interactions with conspecifics, habitat navigation and avoidance of predation. Three types of signal, involving volatile and involatile components, have strong potential for exploitation: pheromones used to recognize safe sites and trails; pheromones involved in sexual attraction and competitive signaling; and predator scents that stimulate avoidance. These signals induce strong innate responses combined with learning that underpins the typical flexible and adaptive use of semiochemicals by mammals. We will build an integrated understanding of the scent components and responses that could be used to improve the effectiveness and targeting of conventional control methods, or to provide new non-rodenticide approaches. This interdisciplinary programme involves specialists in rodent behaviour and scent communication, chemical ecology and biochemistry of volatile and protein pheromones and their carriers. We will combine gas and liquid chromatography, mass spectrometry, NMR, chemical/protein synthesis and scent manipulation, integrated with appropriate behavioural bioassays, to identify and characterise key constituents of both signal and response, and define the dynamics between volatile components and proteins that bind them. Once we have identified and synthesized stimuli that have key effects under laboratory conditions, we will test their ability to replicate or disrupt normal behaviour in semi-natural environments where responses can be fully monitored. A Stakeholder group of relevant national / international industry representatives, external organizations and individual experts will provide guidance to maintain a realistic focus and provide a clear pathway to exploitation.

The scientific outputs from this project will have significant benefits in terms of food security, human and livestock health, the economic impact of infrastructure damage, and the potential for reduced ecological and other damage to non-target species. The potential benefits have both a national and an international perspective as this proposal focuses on rodent species that are worldwide pests and addresses fundamental aspects of the behaviour of rodents and their use of information in scents. The importance of this proposal is highlighted by the level of end-user support (see attached letters of support). Improved food security, gained through better rodent control will have major benefits for: * food producers and retailers, by reducing major losses at all levels of production, storage and distribution of a wide variety of foods; reduced contamination events and the negative impact on consumer perception of brand; * reduction of food costs to the general public and increased food available to undernourished people particularly in developing countries; given the predicted substantial increase in food demand over the next 50 years, it is essential to find more effective ways to reduce pre and post harvest losses to rodents; * reduction in the spread of food-borne diseases through rodent vectors such as Salmonella and Campylobacter, benefiting livestock farmers, the general public, the health services, the catering industry and reduced sickness costs to industry. A reduction in other rodent-borne diseases, such as leptospirosis, lymphocytic chorio-meningitis, pasteurellosis, cryptosporidiosis, toxoplasmosis and swine dysentery, and reduction in rodent allergens correlated with asthma, will benefit: * human health (public, health service and industry benefits); * livestock producers; * environmental health services and hospitals; * the welfare of livestock and other animals including companion, laboratory and zoo animals at risk of rodent-borne infections. Prevention of damage to materials and infrastructure will have major benefits for: * private industry and public services responsible for maintaining infrastructure damaged by rodents; * industry and the general public through reduction in rodent damage, for example to communications and electric cabling, machinery and reduced risk of fires and electrocution; * industry through reduction in damage and spoilage to insulation and packaging materials. Improved targeting and efficiency of conventional rodenticides and traps through the application of scent signals, or the use of information in natural scent deposits to monitor infestations, will provide: * new products and tools for manufacturers, distributors and service companies in the pest control industry or public services; * reduction in the amount and distribution of rodenticide used, reducing the exposure of non-target species such as predators or other non-pest animals that take toxic baits, of increasing concern to regulators and society; * improved efficiency of control at low population densities, reducing the number of individuals killed by rodenticides with commensurate reduction in the welfare costs of rodent control and the exposure of predators and scavengers to toxic prey. The development of additional non-lethal approaches will benefit: * regulators requiring a reduction in the use of rodenticides that are highly persistent in the environment; * the pest control industry and customers seeking alternatives to the use of rodenticides; * industry, environmental health services and the general public, particularly if new European regulation limits the conventional use of rodenticides to control rodents; * societal concerns about the humaneness of rodenticides as the main means of rodent control.