Resident areas and migrations of female green turtles nesting at Buck Island Reef National Monument, St. Croix, US Virgin Islands

Abstract

Satellite tracking studies can reveal much about turtles' spatial use of breeding areas, migration zones, and foraging sites. We assessed spatial habitat-use patterns of 10 adult female green turtles Chelonia mydas nesting at Buck Island Reef National Monument (BIRNM), US Virgin Islands (USVI; 17° 47.4' N, 64° 37.2' W) from 2011 to 2014. Turtles ranged in size from 89.0 to 115.9 cm curved carapace length (CCL) (x ± SD: 106.8 ± 7.7 cm). The inter-nesting period for all turtles ranged from 31 July to 4 November, and sizes of the 50% core-use areas ranged from 4.2 to 19.0 km2. We observed consistency of inter-nesting habitat-use patterns, with all turtles using near-shore (< 1.5 km), shallow waters (< -20 m depth) within approximately 10 km of Buck Island. Seven of the 10 turtles remained locally resident after the nesting season; 5 turtles (50%) established resident foraging areas around Buck Island, 2 established resident foraging areas around the island of St. Croix, and the other 3 (30%) made longer-distance migrations to Antigua, St. Kitts & Nevis, and Venezuela. This is the first empirical dataset showing limited migration and use of 'local' resources after the nesting season in the USVI by this unique management unit of green turtles. Five of the turtles had resident foraging area centroids within protected areas; thus, inter-nesting and foraging areas at BIRNM that overlap with human use zones present an important management concern. Delineating spatial areas and identifying temporal periods of nearshore habitat use can be useful for natural resource managers with responsibility for overseeing vulnerable habitats and protecting marine turtle populations.