114 in 2002-2004, with No Reports Or Indications That These Populations
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2 1 2 1 2 0 2 0 2 3 2 2 2 3 2 2 1 9 1 9 1 8 1 8 Tonle Sap Tonle Sap Lake Lake Mekong Mekong 1 River 1 River 2 2 3 3 4 4 5 5 6 9 6 9 7 8 1 2 7 8 1 2 1 0 1 0 1 1 1 3 PHNOM 1 1 1 3 PHNOM 1 4 1 4 1 5 PENH 1 5 PENH 1 7 1 6 1 7 1 6 Figure 1. Confirmed dry season crocodile sites in Cambodia (2001-2004). Figure 1. Confirmed dry season crocodile sites in Cambodia (2001-2004). in 2002-2004, with no reports or indications that these populations had greatly changed from previous years. There in 2002-2004, with no reports or indications that these populations had greatly changed from previous years. There was however a report of one crocodile (approximately 1.2-1.5 m long) being captured and sold from the Areng River was however a report of one crocodile (approximately 1.2-1.5 m long) being captured and sold from the Areng River in 2004, while another was seen dead on a sand bank after drowning in a net (1.2 m long) also in 2004. in 2004, while another was seen dead on a sand bank after drowning in a net (1.2 m long) also in 2004. Habitat Habitat Siamese Crocodiles were found in oxbow lakes, rivers (wide slow flowing lowland rivers, narrow slow flowing Siamese Crocodiles were found in oxbow lakes, rivers (wide slow flowing lowland rivers, narrow slow flowing mountain rivers), streams and marshes. As surveys were undertaken during the dry season, the water levels were at mountain rivers), streams and marshes. As surveys were undertaken during the dry season, the water levels were at their lowest, and crocodiles were often found in the deepest parts of the remaining water bodies (locally referred to their lowest, and crocodiles were often found in the deepest parts of the remaining water bodies (locally referred to as ‘anlongs’ in rivers). Water was at least 1.2 m deep and slow moving where crocodiles were confirmed. Crocodiles as ‘anlongs’ in rivers). Water was at least 1.2 m deep and slow moving where crocodiles were confirmed. Crocodiles were not found in the shallow water (less than 1.2 m deep) or in the faster flowing sections of rivers or streams. were not found in the shallow water (less than 1.2 m deep) or in the faster flowing sections of rivers or streams. Basking or haul-out areas were often used, and were all within 10 m of the water. Generally the area was flat with a Basking or haul-out areas were often used, and were all within 10 m of the water. Generally the area was flat with a gentle slope to the water. The substrate on which crocodiles were found to bask differed depending on the surrounding gentle slope to the water. The substrate on which crocodiles were found to bask differed depending on the surrounding riverside habitat but included sandy and grassy banks and large flat rocks. In swampy areas crocodiles basked on the riverside habitat but included sandy and grassy banks and large flat rocks. In swampy areas crocodiles basked on the higher areas which were usually covered in various grasses. The worn paths between oxbow lakes and the river were higher areas which were usually covered in various grasses. The worn paths between oxbow lakes and the river were observed on numerous occasions, and these forested tracks often contained mud smeared on fallen trees, and dung. observed on numerous occasions, and these forested tracks often contained mud smeared on fallen trees, and dung. Some tracks were more than 200 m long and were often used in the dry season when water levels were low, as Some tracks were more than 200 m long and were often used in the dry season when water levels were low, as crocodiles moved between the lake and river. crocodiles moved between the lake and river. Riparian habitat disturbance did not seem to affect the distribution of crocodiles along a river system, unless it was Riparian habitat disturbance did not seem to affect the distribution of crocodiles along a river system, unless it was associated with current human presence. Areas adjacent to previously disturbed forest, such as an abandoned village associated with current human presence. Areas adjacent to previously disturbed forest, such as an abandoned village or agricultural swidden, still contained crocodiles but this may be because these areas represented relatively small or agricultural swidden, still contained crocodiles but this may be because these areas represented relatively small disturbances in large areas of the intact riparian vegetation. Crocodiles were generally not found in rivers adjacent to disturbances in large areas of the intact riparian vegetation. Crocodiles were generally not found in rivers adjacent to villages or areas active with human disturbance. villages or areas active with human disturbance. Diet Diet 291 dung samples were collected and assessed for undigested prey items. These samples came from numerous 291 dung samples were collected and assessed for undigested prey items. These samples came from numerous rivers, lakes and marshes, and include samples from a wide range of crocodile sizes, from small to large animals. rivers, lakes and marshes, and include samples from a wide range of crocodile sizes, from small to large animals. 114 114 40 40 35 35 30 30 25 25 20 20 15 15 Percentage 10 Percentage 10 5 5 0 0 Snake Fish Insect Mammal Bird Nothing Snake Fish Insect Mammal Bird Nothing Figure 2. Percentage number of dung found with undigested prey items found in Siamese Crocodile Figure 2. Percentage number of dung found with undigested prey items found in Siamese Crocodile dung (n= 291, all age classes). Note that dung often had more than one prey item represented. dung (n= 291, all age classes). Note that dung often had more than one prey item represented. Figure 2 represents the results of these pooled data and shows that Siamese Crocodiles seem to be generalist feeders, Figure 2 represents the results of these pooled data and shows that Siamese Crocodiles seem to be generalist feeders, preying on a wide variety of prey items. preying on a wide variety of prey items. Further analysis is required to determine differences in diet between adults and juveniles or populations in different Further analysis is required to determine differences in diet between adults and juveniles or populations in different parts of their range A large proportion of the dung did not contain any undigested prey items at all, but these samples parts of their range A large proportion of the dung did not contain any undigested prey items at all, but these samples were usually small sized, and hence from small animals. These crocodiles have possibly been feeding on tadpoles or were usually small sized, and hence from small animals. These crocodiles have possibly been feeding on tadpoles or frogs that were digested completely, leaving no trace of the prey. The larger dung from some areas provided numerous frogs that were digested completely, leaving no trace of the prey. The larger dung from some areas provided numerous fish scales, while other areas showed few fish scales but many snakes scales and mammal hair. This indicates that the fish scales, while other areas showed few fish scales but many snakes scales and mammal hair. This indicates that the dominant prey taken varies in different rivers and probably different times of the year. dominant prey taken varies in different rivers and probably different times of the year. Nesting Nesting Four active nests were found in 2004 and are the first wild Siamese Crocodile nests documented in Cambodia. These Four active nests were found in 2004 and are the first wild Siamese Crocodile nests documented in Cambodia. These nests will be described in detail elsewhere but are summarized in Table 2. Nesting occurred at the start of the wet nests will be described in detail elsewhere but are summarized in Table 2. Nesting occurred at the start of the wet season, with all clutches being laid in April. Hatchlings are expected to emerge in June, but this is dependent on season, with all clutches being laid in April. Hatchlings are expected to emerge in June, but this is dependent on climatic conditions and so may change slightly from year to year. Nests were typical vegetation mounds and 3 were climatic conditions and so may change slightly from year to year. Nests were typical vegetation mounds and 3 were found at oxbow lakes while one was in swamp habitat. Three of the nests were well shaded for most of the day except found at oxbow lakes while one was in swamp habitat. Three of the nests were well shaded for most of the day except for the Nest #4 (Table 2) which was mostly exposed on a floating vegetation mat. Clutch sizes ranged from 16 to 25 for the Nest #4 (Table 2) which was mostly exposed on a floating vegetation mat. Clutch sizes ranged from 16 to 25 (Table 2), which is considerably less than the 50 eggs recorded for C. siamensis in captivity (Youngprapakorn et al. (Table 2), which is considerably less than the 50 eggs recorded for C. siamensis in captivity (Youngprapakorn et al. 1971). 1971). Table 2. Nest characteristics for wild Siamese Crocodile nests, 2004. CS= clutch size, Flt. Mat = floating Table 2. Nest characteristics for wild Siamese Crocodile nests, 2004. CS= clutch size, Flt.