Seabird recovery and vegetation dynamics after Norway rat eradication at Tromelin Island, western Indian Ocean

Published source details Le Corre M., Danckwerts D.K., Ringler D., Bastien M., Orlowski S., Rubio C.M., Pinaud D. & Micol T. (2015) Seabird recovery and vegetation dynamics after Norway rat eradication at Tromelin Island, western Indian Ocean. Biological Conservation, 185, 85-94.
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Summary

Birds

Control mammalian predators on islands for seabirds

A before-and-after study in 2005-2006 and 2012-2013 on Tromelin Island, southwest Indian Ocean (Le Corre et al. 2015) found that eradicating introduced Norway rats Rattus norvegicus and controlling house mice Mus musculus resulted in increased breeding populations of red-footed boobies Sula sula and masked boobies Sula dactylatra plus establishment of breeding populations of white terns Gygis alba and brown boobies Sula leucogaster. Red-footed boobies increased 23% per year without apparent immigration (2005: 130 pairs; 2013: 855 pairs). Masked boobies increased 22% per year (2005: 224 pairs; 2013: 1,090 pairs). Rats were eradicated after poisoning but mice, although initially reduced, reached high density in 2012-2013 (dry season: 32 mice/ha; rainy season: 52 mice/ha). Poisoning took place in 2005-2006 with bait stations (Pestoff Rodent Blocks; 25 kg in total) and manual applications across the island of pellets (Pestoff Rodent Bait 20R; one tonne). Seabirds were counted multiple times (2005-2006; 2008; 2012-1013). Tromelin is a 100ha island. (Clazina Kwakernaak)

Plants

A before-and-after replicated study in 2005-2006 and 2012-2013 on Tromelin Island, southwest Indian Ocean (Le Corre et al. 2015) found that eradication of introduced Norway rats Rattus norvegicus and control of house mice Mus musculus resulted in increased coverage by the herb Boerhavia diffusa, but not shrubs. Over eight years, cover of Boerhavia diffusa (a rat food source) increased in two plots (from 10% to 60%, and 40% to 80%) and remained unchanged (70% to 80%) in a third plot. Shrub and sparse herbaceous cover (6 plots) remained unchanged (data not provided). Mice numbers dropped after poisoning in 2005-2006 but reached high density by 2012-2013 (dry season: 32 mice/ha; rainy season: 52 mice/ha). Poisoning took place in 2005-2006 with bait stations (Pestoff Rodent Blocks; 25 kg in total) and manual pellet applications across the island (Pestoff Rodent Bait 20R; one tonne). Nine 10 x 10m vegetation plots were surveyed. Tromelin is a 100ha island. (Clazina Kwakernaak)

Invasives

Control non-native mammals

A before-and-after study in 2005-2006 and 2012-2013 on Tromelin Island, southwest Indian Ocean (Le Corre et al. 2015) found that combined bait station and manual poison applications eradicated introduced Norway rats Rattus norvegicus but not house mice Mus musculus. No rats were captured after poisoning in 2005-2006. Mice were not seen for six months after poisoning but reached high density by 2012-2013 (dry season: 32 mice/ha; rainy season: 52 mice/ha). No seabird accidental poisoning was observed. Poisoning was carried out in 2005-2006 with bait stations containing 0.02 g/kg brodifacoum (Pestoff Rodent Blocks) and manual pellet applications (Pestoff Rodent Bait 20R). Bait stations were placed on 20cm high poles in a 100 x 100 m grid (checked for four weeks; 25 kg bait in total). One tonne of pellet baits was manually spread across the whole island (100ha; single application; 10 kg/ha). Rats and mice were monitored in 2012-2013 (30 nights; 60 traps). (Clazina Kwakernaak)