Severity of the Effects of Invasive Rats on Seabirds: A Global Review

Abstract

Invasive rats are some of the largest contributors to seabird extinction and endangerment worldwide. We conducted a meta-analysis of studies on seabird-rat interactions to examine which seabird phylogenetic, morphological, behavioral, and life history characteristics affect their susceptibility to invasive rats and to identify which rat species have had the largest impact on seabird mortality. We examined 94 manuscripts that demonstrated rat effects on seabirds. All studies combined resulted in 115 independent rat-seabird interactions on 61 islands or island chains with 75 species of seabirds in 10 families affected. Seabirds in the family Hydrobatidae and other small, burrow-nesting seabirds were most affected by invasive rats. Laridae and other large, ground-nesting seabirds were the least vulnerable to rats. Of the 3 species of invasive rats, Rattus rattus had the largest mean impact on seabirds followed by R. norvegicus and R. exulans; nevertheless, these differences were not statistically significant. Our findings should help managers and conservation practitioners prioritize selection of islands for rat eradication based on seabird life history traits, develop testable hypotheses for seabird response to rat eradication, provide justification for rat eradication campaigns, and identify suitable levels of response and prevention measures to rat invasion. Assessment of the effects of rats on seabirds can be improved by data derived from additional experimental studies, with emphasis on understudied seabird families such as Sulidae, Phalacrocoracidae, Spheniscidae, Fregatidae, Pelecanoididae, Phaethontidae, and Diomedeidae and evaluation of rat impacts in tropical regions.

Understanding Invasive Species in the Galapagos Islands

“…They prey on seabirds (eggs, chicks, and adults) and are opportunistic feeders and very adaptable to new environments. They can be blamed for seabird extirpation and population decline (Jones et al 2008;Oppel et al 2011). In the case of the Galapagos, many of these unintentional introductions were brought on by early explorers, pirates, and whalers between the fifteenth and eighteenth centuries.…”

Cryptic diversity in Black rats Rattus rattus of the Galápagos Islands, Ecuador

“…The effects of these invasive rodents on endemic biodiversity can be extremely detrimental (Jones et al. 2008; Garba et al. 2014).…”

Eradications of invasive mammals from islands: why, where, how and what next?

“…Seabirds are also major conduits of nutrients to relatively unproductive terrestrial systems, including on islands, allowing them to support dense communities of arthropods and other consumers (Polis and Hurd 1996;Towns et al 2009). The most widespread and detrimental of the introduced species affecting seabirds are Norway (Brown) Rat (Rattus norvegicus), Black (Ship or Roof) Rat, and Polynesian Rat or Kiore (R. exulans), which affect large, surface-nesting albatrosses, frigatebirds and larids least, and small, burrow-nesting storm petrels and other ecologically similar taxa greatest; however, even adults as large as Laysan Albatrosses (Phoebastria immutabilis) are vulnerable to predation by Polynesian Rats (Jones et al 2008). Recent work at Gough Island indicates that the introduced House Mouse, which was formerly not considered to pose a problem for large seabirds, kills so many Tristan Albatrosses (Diomedea dabbenena) chicks that the population is unlikely to recover even if the other key threat, fisheries-related mortality of adults and juveniles, were eliminated ).…”