Rats are not the only introduced rodents producing ecosystem impacts on islands

Abstract

In addition to rats, nutria (Myocastor coypus) and the North American beaver (Castor canadensis) have certainly caused damage at an ecosystem level when introduced to islands, in both cases primarily by ecosystem engineering. Of other introduced rodents successfully established on islands, the gray squirrel (Sciurus carolinensis) may be in the process of damaging entire forest ecosystems, particularly by bark-stripping. Though introduced muskrats (Ondatra zibethicus) have had ecosystem-level impacts in continental Europe, their impact on islands worldwide to which they have been introduced has been very limited. The North American red squirrel (Tamiasciurus hudsonicus) and Barbary ground squirrel (Atlantoxerus getulus) have each had substantial impacts when introduced to particular islands, but for neither species have these impacts yet been demonstrated to spread through an entire ecosystem. Introduced house mice (Mus musculus) may well generate ecosystem impacts on remote islands lacking rats, and it is possible that explosions of house mice on islands after rat eradication, a common occurrence, will lead in some instances to ecosystem impacts.

Review of negative effects of introduced rodents on small mammals on islands

“…By 'introduced' I refer to a species that has been accidentally or deliberately transported, by human activity, to a location outside its natural range. Although various rodent species have been introduced onto islands (Musser and Carleton 2005;Simberloff 2008), four species are commonly considered conservation problems and are the focus of this review: the black rat Rattus rattus, Norway rat R. norvegicus and Pacific rat R. exulans and the house mouse Mus musculus.…”

Direct and Indirect Interactions between Landscape Structure and Invasive or Overabundant Species

“…In these cases, the presence of or proximity to certain land uses within a landscape may serve as sources of individuals or propagules for invasion, accommodate critical life stages, or meet the ecological requirements of species. Propagule pressure from certain landscape elements promotes successful invasion in part by reducing the effects of demographic and environmental stochasticity [35,36]. Amur honeysuckle (Lonicera maackii), an invasive shrub widely used in urban landscapes, illustrates this point well.…”

“…Many ecosystem engineers are underrecognized for their roles. For example, introduced mammals on islands are well known for their disastrous effects as predators, but many also are ecosystem engineers, as demonstrated for nutria (Myocastor coypus), beaver, gray squirrel (Scurius carolinensis) [36] and deer [79]. Non-native invasive bivalves, such as zebra mussels, also act as aquatic ecosystem engineers, altering the structure and function of within-lake landscapes [80].…”

Invasive rodents on islands: integrating historical and contemporary ecology

“…Simberloff (2008) systematically reviews the range of rodent species that have been introduced to islands (often deliberately) and points out their potential for ecosystem-level impacts. Finally, Angel et al (2008) review the effects of the widely-distributed but underappreciated house mouse (Mus musculus) on islands in the Southern Ocean, where it is increasingly recognized as a conservation threat (Wanless et al 2007), especially on islands lacking other introduced mammals.…”