Data sets

Population and available suitable habitat estimates for green turtles (Chelonia mydas) and hawksbills turtles (Eretmochelys imbricata) in the Chagos Archipelago.


Type
Subject
biological_organisms
Lifeform
turtle
Stress
Contact
Dr Jeanne A Mortimer
Contact email
mortimer@.ufl.edu
Start year
1996
End year
1996
Resource lineage
Data format
xlsx
Description
During a six-week period in February/March 1996, a survey of 49 islands and 110 of the 226 km of the total coastline of the Chagos Archipelago . Most data on nesting populations and habitats were gathered by walking around the perimeter of each island at a steady pace while recording the relationship between the time, GPS reading and the physical characteristics of the offshore area, the foreshore, and the beach platform. The locations and characteristics of all turtle “tracks” and body “pits” (defined below) were recorded. These data were correlated with measurements taken from charts in order to map the available nesting habitat and the extent to which it was utilized.All stretches of surveyed coastline were scored as to whether or not they were suitable for turtle nesting. Suitable coastline was defined as that having a sand beach platform well enough developed to allow at least some nesting, along with a foreshore and an offshore approach that would not completely obstruct the emergence of a turtle from the sea.Coastline rated as suitable included nesting habitats that varied greatly in quality.**TABLE 1.** Comparison of five atolls in the Chagos Archipelago in terms of body pit density and estimated total body pits for hawksbills and for green turtles.† (Number of body “pits” counted) / (Number of km “suitable” beach surveyed) per atoll ‡ (Body pit density) * (Estimated total number of km “suitable” beach) per atoll**TABLE 2.** Raw hawksbill shell exported from Chagos into Mauritius during a 13 year period between 1904-1915 and 1929. Data from The Blue Book for the Colony of Mauritius as reported by Frazier 1977. † Bourne (1886)**TABLE 3.** Relative contribution of each atoll to the export of raw hawksbill shell from Chagos to Mauritius during the years 1904-1915 and 1929. Data from The Blue Book for the Colony of Mauritius as reported by Frazier 1977.**APPENDIX 1.** Summary of data collected in Peros Banhos atoll describing the availability of suitable nesting habitat and its utilization by nesting sea turtles at each island.**APPENDIX 2.** Summary of data collected at Salomon atoll describing the availability of “suitable” nesting habitat and its utilization by nesting sea turtles at each island.**APPENDIX 3.**Summary of data collected at islands of the Chagos Bank describing the availability of “suitable” nesting habitat and its utilization by nesting sea turtles at each island. † data collected by Peter Symens# count under-estimates actual number (pers. observ. JAM)**APPENDIX 4.** Summary of data collected at the Egmont Islands describing the availability of “suitable” nesting habitat and its utilization by nesting sea turtles at each island.**APPENDIX 5.** Summary of data collected at Diego Garcia atoll describing the availability of “suitable” nesting habitat and its utilization by nesting sea turtles at each island. † data collected by Peter Symens
Keywords
turtle turtle_pits habitat
Notes
Data extracted from publication by Elizabeth Widman.
Link
Local link
Latitude
0.00000000
Longitude
0.00000000
Status
OA
Clearance
0
Local link
Mortimer and Day 1999.xlsx
Authors
Day M , Mortimer Jeanne .