sentences:  Most of these have since become extirpated from Singapore largely due to rapid urban development, with occasional large mammals such as Asian elephants swimming across the Straits of Johor from Johor, Malaysia.Many surviving species have critically low population numbers, the most seriously endangered being the cream-coloured giant squirrel, last sighted in 1995 and now possibly extirpated.The banded leaf monkey is also down to around 50 individuals.