Nest Site Selection and Egg Characteristics of the Monitor Lizard (Varanus niloticus) in Anambra Floodplain, South East Nigeria

This study investigates nest site selection and egg characteristics of the Nile Monitor Varanus niloticus in the Anambra River floodplain, Anambra State, located in Nigeria's South East geopolitical zone. Varanus niloticus is widely harvested for bushmeat and the international leather trade, and population pressure necessitates understanding its reproductive ecology for management purposes. Nest searching was conducted systematically along 15 km of riverbank and adjacent vegetation using trained observers during and immediately after the wet season. A total of 23 active nests were located and characterised for substrate type, distance to water, aspect, Zoologyh, and vegetation cover. Ten nests were excavated after hatching to record egg number, dimensions, and hatchling size. Female body size was measured from animals captured opportunistically near nest sites. Mean clutch size was 22 eggs (range 14 to 37). Egg incubation duration averaged 165 days based on nest timing and hatchling emergence. Termite mounds were used for 52 percent of nests, riverbank sandy soil for 35 percent, and rotting vegetation for 13 percent. Nest site selection showed strong preferences for elevated, sun-exposed locations near permanent water. Larger females produced significantly more eggs. Hunting pressure was high, with evidence of human nest predation at 8 of 23 sites. The study recommends legal protection of nesting sites and size-specific harvest restrictions to sustain Varanus niloticus populations in the Anambra floodplain. Keywords: Varanus niloticus, nest site selection, reproductive ecology, Anambra floodplain, monitor lizard.