A mechanistic understanding of prebaiting to improve interaction with wildlife management devices

Developing fertility control for rodents: a framework for researchers and practitioners

Fertility control is often heralded as a humane and effective technique for management of overabundant wildlife, including rodents. The intention is to reduce the use of lethal and inhumane methods, increase farm productivity and food security as well as reduce disease transmission, particularly of zoonoses. We developed a framework to guide researchers and stakeholders planning to assess the effectiveness of a potential contraceptive agent for a particular species. Our guidelines describe the overarching research questions which must be sequentially addressed to ensure adequate data are collected so that a contraceptive can be registered for use in broad-scale rodent management. The framework indicates that studies should be undertaken iteratively and, at times, in parallel, with initial research being conducted on (1) laboratory-based captive assessments of contraceptive effects in individuals; (2) simulation of contraceptive delivery using bait markers and/or surgical sterilization of different proportions of a field-based or enclosure population to determine how population dynamics are affected; (3) development of mathematical models which predict the outcomes of different fertility control scenarios; and (4) implementation of large-scale, replicated trials to validate contraceptive efficacy under various management-scale field situations. In some circumstances, fertility control may be most effective when integrated with other methods (e.g. some culling). Assessment of non-target effects, direct and indirect, and the environmental fate of the contraceptive must also be determined. Developing fertility control for a species is a resource-intensive commitment but will likely be less costly than the ongoing environmental and economic impacts by rodents and rodenticides in many contexts.

Assessing Two Different Aerial Toxin Treatments for the Management of Invasive Rats

Aotearoa–New Zealand has embarked on an ambitious goal: to completely eradicate key invasive mammals by 2050. This will require novel tools capable of eliminating pests on a large scale. In New Zealand, large-scale pest suppression is typically carried out using aerial application of the toxin sodium fluoroacetate (1080). However, as currently applied, this tool does not remove all individuals. A novel application method, dubbed ‘1080-to-zero’, aims to change this and reduce the abundances of target pests to zero or near-zero. One such target is black rats (Rattus rattus), an invasive species challenging to control using ground-based methods. This study monitored and compared the response of black rats to a 1080-to-zero operation and a standard suppression 1080 operation. No difference in the efficacy of rat removal was found between the two treatments. The 1080-to-zero operation did not achieve its goal of rat elimination or reduction to near-zero levels, with an estimated 1540 rats surviving across the 2200 ha treatment area. However, 1080 operations can produce variable responses, and the results observed here differ from the only other reported 1080-to-zero operation. We encourage further research into this tool, including how factors such as ecosystem type, mast fruiting and operational timing influence success.

Inhibition of serotonergic signaling induces higher consumption of both sucrose solution and toxic baits in carpenter ants

Biogenic amines play an important role in the regulation of appetitive responses in insects. Among them, serotonin (5-HT) regulates feeding-related processes in numerous insect species. In carpenter ants, 5-HT administration has been shown to depress feeding behavior, thus opening the possibility of using 5-HT modulation in control strategies against those species considered as pest. Here we studied if administration of a 5-HT antagonist, ketanserin, promotes feeding of a sucrose solution and a toxic bait in carpenter ants Camponotus mus. We found that 3 h after a single oral administration of ketanserin, the mass of sucrose solution consumed by carpenter ants increased significantly. A similar effect was found after a chronic administration that lasted 5 days. Yet, ketanserin did neither affect the intake rates nor the activity of the pharyngeal pump that mediates feeding dynamics. In addition, ketanserin promoted the consumption of a toxic bait based on boric acid. Our results thus show that feeding motivation and consumption of both sucrose solution and a toxic bait can be enhanced via prior administration of ketanserin. We discuss the possible mechanisms underlying these effects and conclude that understanding basic physiological and neural principles that underlie feeding motivation allows establishing more efficient control strategies for pest insects.