Report on the reptiles of Upland Savai’i

Abstract

The reptile team conducted a 21 kilometre transect from the coast east of Asau to the uplands ending near Mauga Silisili at over 1720 m elevation. This transect covered the main habitats on Savai’i and allowed the team to determine where various reptile species and invasive species occurred across this elevational gradient. No previous reptile research had taken place on Savai’i above the elevation of A’opo Village. Limited sampling was also done around the Forestry Station in Asau. The team detected 11 species of lizards during these surveys, which is the majority of species known from Samoa. Noticeably absent was the Pacific black skink (Emoia nigra), which is a dominant element of the Samoan lizard fauna. Also no individuals of the Pacific boa (Candoia bibroni) were detected despite the concentrated effort spent looking for them. One boa was detected by the avifauna team at their Site 1, by the TV tower on a log in a marsh. The invasive house gecko (Hemidactylus frenatus) was also not detected along the main transect, but was the most abundant gecko on buildings in Asau. No reptiles were found above 1320 m elevation and most species were found significantly below there. Snakeeyed skinks (Cryptoblepharus poecilopleurus) were detected on Savai’i for the first time at Asau Getaway Resort then above the sawmill on the way to A’opo. Since western Savai’i is so poorly known for reptiles, this is the first time many of these species were recorded from this part of the island. Surveys for invasive species detected mammalian species (cats, rats, and pigs) and invertebrate species (Yellow Crazy ants and Big-headed ants). The mammals were found at various sites along the transect, including high elevations. The ants were found at lower elevations along the transect, but the Yellow Crazy ants appear to be irrupting currently on Savai’i and were swamping our traps from sea level to 500 m elevation. The low elevation lizard occurrences from sea level to 500 m appeared impaired by the invasive ants. Although habitat looked good in many places along the transect, certain species were rare or absent when the invasive ants were present, e.g. the Samoan skink (Emoia samoensis) which only occurred at elevations higher than the ants, whereas elsewhere in its range it occurs down to sea level. Currently the uplands over 500 m are free of invasive ants. We know from Hawai’i that invasive ants occur to over 2,000 m elevation and are ecologically very destructive to native flora and fauna. There is an immediate need to try to stop this upward ant invasion to protect this at-risk ecosystem, and to study the intact system now prior to an invasion.