Rapid assessment for a new invasive species threat: the case of the Gambian giant pouched rat in Florida

Abstract

The Gambian giant pouched rat (Cricetomys gambianus) is a large rodent that has established a breeding population in the Florida Keys. Should it successfully disperse to mainland Florida, it could continue spreading through much of North America where significant negative ecological and agricultural consequences could result. We rapidly developed the information for implementing an efficient and successful eradication program before dispersal to the mainland occurs. This included development of monitoring and indexing methods and their application to define the animal’s range, the development of baits attractive to Gambian giant pouched rats, efficacy testing of toxicants, and development of bait-delivery devices that exclude native animals. Gambian giant pouched rats appeared confined to the western two-thirds of Grassy Key, but have dispersed across a soil-filled causeway west to Crawl Key. We identified preferred habitat characteristics and potential dispersal pathways. We developed photographic and tracking tile methods for detecting and indexing Gambian giant pouched rats, both of which work well in the face of high densities of non-target species. We identified a commercial anticoagulant bait and we developed a zinc phosphide (an acute toxicant) bait matrix that were well accepted and effective for controlling Gambian giant pouched rats. We also developed a bait station for delivering toxic bait to Gambian giant pouched rats without risk to native species. We consider that the criteria are met for a successful eradication to commence.

Taxonomy of the African giant pouched rats (Nesomyidae: Cricetomys): molecular and craniometric evidence support an unexpected high species diversity

“…The distribution of this rodent (genus Cricetomys ) spans almost the whole of sub‐Saharan Africa, stretching from the savannah zone of West Africa through the Guineo‐Congolian forest block to the savannahs of East and southern Africa (Musser & Carleton, 2005). These rodents have been proven to be carriers of disease pathogens (Machang'u et al ., 2004; Durnez et al ., 2008) and recent reports show that they are potential pest species as invasive populations have been discovered in the Florida Keys in the USA (Engeman et al ., 2006, 2007; Perry et al ., 2006; Peterson et al ., 2006).…”

Invasive Rodent Ecology, Impacts, and Management with an Emphasis on the United States

“…Rodents can be prolific on islands where they have few or no predators. Their omnivorous foraging has led to the endangerment or extinction of numerous island species, especially bird species (Moors and Atkinson 1984, Witmer et al 1998, Veitch and Clout 2002, Engeman et al 2006, Veitch et al 2011. While their impacts to seabirds have long been known, invasive rodents also impact seeds and seedlings, invertebrates, sea turtle eggs and hatchings, and other resources (Witmer et al 2007a, Caut et al 2008, Angel et al 2009, Towns et al 2009, Drake et al 2011, St Clair 2011, Shiels et al 2014.…”

Wild Pigs

“…They had become popular in the pet industry and likely were released by a pet breeder and subsequently became established on Grassy Key in the Florida Keys in 1999 (Engeman et al 2006;Perry et al 2006). Despite a prolonged eradication effort, a free-ranging and breeding population remained on the island (Engeman et al 2006(Engeman et al , 2007Witmer and Hall 2011). There is a concern that if this species reaches the mainland, there could be damage to the Florida fruit industry because Gambian rats are known to damage numerous types of agricultural crops in Africa (Fiedler 1994).…”

“…Their high reproductive potential, omnivorous foraging strategy, and aggressive predatory behavior have led to the endangerment or extinction of numerous native island species, especially birds (Moors and Atkinson 1984;Witmer et al 1998;Veitch and Clout 2002;Engeman et al 2006;Towns et al 2011). While their impacts to seabirds have been long known, invasive rodents also impact seeds and seedlings, invertebrates, sea turtle eggs and hatchings, and other parts of the ecosystem (Witmer et al 2007a;Caut et al 2008;Angel et al 2009;Towns et al 2009;St Clair 2011;Drake et al 2011).…”