Cities share a distinct group of animals such as rats, pigeons and cockroaches that have evolved to live off human resources. We explore when, how and why these exotic urban specialists encroach into bushland, what determines whether they establish, and what are the ecological consequences. We argue that urban specialists are native to urban landscapes, but that urban resources sometimes help them spillover into natural areas to affect local wildlife and spread disease.

Rodents are major crop pests and they are also hosts of important rodent-borne diseases in South-east Asia, for which infection risks to humans are affected by ongoing land use changes. Improvement of rodent taxonomy, thanks to molecular tools, and phylogenetic reconstruction allow a better description of the distribution of major rodents and their associated rodent-borne diseases among habitats. Our review shows that the structure of landscape affects the likely presence of rodent-borne diseases.

Understanding recovery mechanisms of small rodents is important to improve strategies for pest management and conservation based on the target species’ ecology. Published information indicates that population recovery after sudden collapse strongly depends on factors such as life-history strategy, social behaviour, and density-dependent processes. Findings suggest to make case-by-case decisions for small scale conservation issues and to manage r-selection strategist pest rodents on a large spatial scale, including refuge areas, and to monitor for survivors after a couple of months. Photograph of a common vole (Microtus arvalis) by Jens Jacob.

Ecosystems are under threat from global stressors that reduce their resilience. We investigated how land use and climate change (two such stressors) could impact the diversity and resilience of a small mammal community in East African savanna ecosystems. Agro-ecosystems were less likely to contain specialist species compared to protected natural ecosystems, with the consequence that land use intensification and projected changes in climate may compromise the future resilience of the small mammal community in this tropical savanna ecosystem. Photograph by Andrea Byrom.

Globally, rats and mice annually eat and spoil cereals that could feed ~280 million people in developing countries alone. This figure is based mainly on pre-harvest losses. Our paper reports post-harvest losses of rice in rural households of 2.5% in Bangladesh and 17% in Myanmar; losses that were reduced to 0.5% and 5%, respectively, through community level control and improved hygiene of granaries. Large post-harvest losses by rats and mice are of significant concern for food security and are preventable.

Toe clipping is a cheap and efficient method for marking rodents, yet its effect is not well known. Using a 17-year capture–mark–recapture dataset in which mice were individually marked using toe clipping, we found no evidence for a biologically significant effect of clipping. We did observe that when mice were trapped for the first time, there was an effect on body condition and a scare effect, where they moved further away from the trap location.

Mutualistic interactions between animals and plants affect plant structure and regeneration. We assessed the effects of plant–rodent functional traits on the formation of mutualistic and predatory interactions between five tree species and six rodents. Both body size of rodents and seed traits are key factors in the formation of mutualistic and predatory interactions within this plant–rodent system. To promote seedling recruitment in degenerated forests, introducing or protecting large-sized scatter hoarders and reducing pure seed eaters are needed. Photograph by Hongmao Zhang.

Stone-bunds built primarily to reduce soil erosion by runoff in Ethiopian highlands are raising concerns among farmers and pest control experts that they may act as refugia for rodents. Following a recent report that fields with high stone-bund density harbor more rodents and endure more crop damage than fields with low stone-bunds, we investigated if the same scenario holds true for reproduction and survival. We found that variation in stone-bund density has a minor influence on reproduction and survival, but the rodents investigated show high local survival rates. Photograph by Yonas Meheretu.

In developing countries, losses caused by rodents to agricultural crops are an important threat to food security and farmer livelihood. In complex agroecosystems in the Philippines, where rodents cause significant rice yield loss, our paper reports that the rice crop stage is a major factor influencing habitat use and breeding biology of the pest rodent species. By understanding the ecology of the pest species, we developed rodent management strategies to reduce both yield losses and costs of rodent control.

Because boreal ecosystems in the Northern Hemisphere are relatively simple, dramatic changes in the abundance of any one wildlife species can have widespread and unpredictable effects. Here we document the disappearance of a once common herbivore from the montane boreal forests of SW Yukon, and report on experiments designed to clarify the causes of population collapses. Our findings point to the intensified role of predation in this system, whose influences likely extend to other prey species.

Invasive rodents are a major cause of bird population declines on islands, and prioritisation of rodent eradications needs the support of robust quantitative data of rodent impacts. Our literature review on the methods used to assess rodent impacts on birds showed a lack of direct field evidence of predation and an overall poor quantification of impacts at the bird population level. We highlight some recommendations on how to strengthen current approaches and extend our knowledge on the mechanisms of impacts.

Plague is a major health threat globally and in particular Africa, where active foci have been reported in several countries including Madagascar, Democratic Republic of Congo, Tanzania and Uganda. Rodents are the main reservoir hosts from which the bacterium is transmitted to humans by fleas. The study in Tanzania shows complex association and interactions between rodents and fleas in various habitats including human settlements. Management of plague outbreaks should focus on reducing interactions between rodents, fleas and people to prevent infections. Photograph: child infected with the bubonic plague in teh Rift Valley District, Tanzania.