Population ecology of the elongated tortoise Indotestudo elongata (Blyth, 1853) at Ban Kok, Khon Kaen province

Abstract

Population ecology of the elongated tortoise Indotestudo elongata was studied at Ban Kok Village, Khon Kaen Province, northeastern Thailand, from 2007-2010. A total of 1,195 tortoises; 396 males, 369 females, and 430 unsexed juveniles were captured by total count method. Population density in a study area of 492 ha was 2.25 individuals per ha. The age and size structure exhibited normal pattern and the average sex ratio (males: females) was 1.07: 1. The early stage and adult stage were high. Only a small number of young tortoises in each class could develop to replace the higher class of population. Tortoises at any stage had a risk from various causes such as from car accident, fire from burning and landscape modification by local people. The growth rates were more rapid during juvenile and sub-adult stages and decreased markedly at adult stage. Males reached sexual maturity at a smaller size and less age than females. Ontogenic changes, distinguished by a marked decrease or increase of allometric growth after tortoises reach sexual maturity, led into sexual dimorphism in 29 characters. Females displayed larger size and had relatively wider carapace and plastron than males. Mating behavior started from May to August. Laying egg occurred at the end of the rainy season (October) until March. Hatchlings emerged at the beginning of the following rainy season (April to June). Female could produce more than one clutch in a season. Mean clutch size was 4.53 ± 2.26 per clutch. Percentage of hatching success was high but survival rate was low. The causes of mortality of hatchlings in the study area were from car traffic, trampling by large cattle, and unknown cause. This species could consume a variety of foods such as herbaceous leaves, fruits, mushroom, grass, earthworm, carcass, food particles and animal excrement. Both juveniles and adults could feed on the same food types. Predator was not found in the study area. There were no ectoparasites on tortoise body, whereas nematodes (round worm and thread worm) were observed from fecal samples. Results of this study indicated that elongated tortoise population at Ban Kok Village has not been threatened severely. However, short term and long term monitorings should be continuously conducted.