Population density and seasonal activity of the threatened Madagascar spider tortoise (Pyxis arachnoides arachnoides) of the southern dry forests; South West Madagascar

摘要

The Madagascar spider tortoise Pyxis arachnoides is facing pressure from habitat destruction, hunting for food and collection for the exotic pet-trade. Very little is known of the biology and ecology of P. arachnoides. This study centres on a subspecies population of P. arachnoides arachnoides, within the southern dry forests of the Anakao region of southwest Madagascar. Surveys were carried out across 83, one hectare, quadrants over 12 months, during both the wet and dry seasons, with respective seasonal mean population densities recorded at 4.63 and 2.08 individuals per ha. This significant variation was accompanied by a variation in micro habitat preference between the seasons, with P. a. arachnoides moving to areas of greater vegetation cover during the warmer wet season. P. a. arachnoides was only recorded as feeding during the wet months, a period of increased activity. The subspecies became less active during the dry season, with some individuals entering a dormant phase. There was generally a greater abundance of females encountered throughout the year, usually weighing less than males. Juvenile abundance peaked during February and March. Six-year-old specimens were the most regularly encountered individuals and a mean age throughout the survey was recorded at 11.25 years.