Reintroduction when threats still exist 345
Plethodon shermani (Connette & Semlitsch, 2013; Karlin et al., 2016). Recovery of large carnivores such as the lynx Lynx lynx, grey wolf Canis lupus lupus and wolverine Gulo gulo in Europe is largely a result of advances in the man- agement of functional landscapes (Chapron et al., 2014). Successional forests are allowing previously overexploited animals that suffered habitat loss, such as the Puerto Rican parrot Amazona vittata and white-crowned pigeon Patagioenas leucocephala, to recover in Puerto Rico and throughout the Caribbean (Earnhardt et al., 2014; Rivera- Milán et al., 2016). Networks of suitable habitat have been modelled for the Iberian ibex Capra pyrenaica in western Iberia (Torres et al., 2016) and for the North Island robin Petroica longipes in New Zealand (Armstrong & Davidson, 2006). These cases highlight how landscape change over time can support species reintroduction and recovery. New ideas are emerging for the reintroduction of species
to their historic ranges when threats are still perceived to be present (Stier et al., 2016). For example, the milu Elaphurus davidianus became extirpated as a result of hunting and habitat conversion for land reclamation in China in the early 20th century, but a wild population became established in 1998 from 36 animals that escaped from a nature reserve during a flooding event. Now, .500 milu descended from those founders persist in the wild (Yang et al., 2016). The Formosan clouded leopard Neofelis nebulosa, considered extinct in Taiwan, is now thought to be a candidate for re- introductions in regenerating forests with rebounding prey bases (Chiang et al., 2015). A reported sighting in 2019 and other unconfirmed sightings strengthen the case for rein- troductions (Everington, 2019). We suggest that suitable habitats and networks of refugia
may exist as a result of landscape regeneration on Caribbean islands that historically lost 30–97% of native land cover to agricultural conversion. This historic land-cover change, since the 1740s, coincided with introductions of invasive spe- cies, creating multiple drivers for island extinctions (Lugo & Helmer, 2004).We studied the Endangered St Croix ground lizard Pholidoscelis polops (historically known as Ameiva polops), which was extirpated from 99.97%of its historic range on the main island of St Croix (217 km2) after the 1884 introduction of the small Indian mongoose Herpestes auropunctatus. The extirpation is thought to be a result of both the conversion of 90% of the island to agricultural pas- tures and predationbymongooses (Henderson, 1992).Recent translocations (1989 and 2008) to two additional small is- lands without mongooses were successful (Fitzgerald et al., 2015). Reintroduction to the main island was not recom- mended historically because the presence of mongooses on St Croix was perceived to prevent population establishment (Meier et al., 1990). Here we explore the alternate view, sug- gesting that even though mongooses are still present on St Croix, regenerating landscapes in the post-agricultural period
create new opportunities for the reintroduction of the St Croix ground lizard. We predicted that areas appropriate for reintroduction
exist based on similarities between the historic (1750) and re-emergent (2016) land-cover types on St Croix. We as- sessed the suitability of potential lizard habitat using land- scape parameters (topography, land cover, elevation) dev- eloped with data collected from the largest extant population on an offshore island (Angeli et al., 2018). We collected data on the distribution of mongooses across St Croix, and used a prioritization scheme to rank suitable reintroduction areas (Dawson et al., 2015). Our work demonstrates how changing landscapes present new opportunities for restoration in historic ranges, especially on islands, even when threats still exist on a broader landscape scale.
Study area and species
St Croix is a 218 km2 island in the Caribbean Sea and one of the U.S. Virgin Islands. It is a single land bank, erupting from the ocean where tectonic plates merged, surround- ed by trenches .1,000 m deep (Case & Holcombe, 1980). The island is covered by subtropical dry coastal forest, with annual rainfall of 1,250 mm in the west and 750 mm in the east (Bowden, 1968). Easterly trade winds blow across the island throughout the year. In addition to the main is- land, there are four small offshore islands, with a total area of 85 ha, off the north and south shores: Protestant Cay, Green Cay, Ruth Island and Buck Island. The main island has been mapped since 1750, but only
one land-cover map from 1750 still exists (Hopkins, 1989). The acreage of plantations increased island-wide during 1742–1754 (Westergaard, 1938), transitioning from cotton to sugar cane during 1754–1800 (Tyson, 1992). Mongooses were introduced to control rats Rattus rattus and Rattus norvegicus in sugar cane fields in
1884.By 1917, nearly 90% of native forests and woodlands had been cleared for agriculture or logged (Ward et al., 2000). Sugar cane cultiva- tion virtually ceased by the late 1950s (Atkinson & Marín- Spiotta, 2015). Since then, secondary subtropical forests have developed on St Croix, with naturalized tree species and novel assemblages colonizing former agricultural lands (Atkinson & Marín-Spiotta, 2015). The St Croix ground lizard is a small diurnal ectotherm
that uses a variety of vegetation cover as habitat. It forages in leaf litter for small invertebrate prey (Fitzgerald et al., 2015). The earliest records of the species’ loss are from the 1930s. It was completely extirpated from the eastern end of St Croix by 1920, and the last individuals were observed in Frederiksted on the western end of St Croix in 1969 (Dodd, 1978). Fortunately, two populations persisted on Protestant Cay (2.6 ha; 150 m offshore) and Green Cay
Oryx, 2021, 55(3), 344–351 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319001091
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