The precise population of the Sentinelese is not known. Estimates range from fewer than 40, through a median of around 250, and up to a maximum of 500. In 2001, Census of India officials recorded 39 individuals[4] (21 males and 18 females); however, out of necessity this survey was conducted from a distance and almost certainly does not represent an accurate figure for the population which ranges over the 59.67 km2 (14,700 acres) island.[6] The 2011 Census of India recorded only 15 individuals (12 males and three females).[1] Any medium- or long-term effect on the Sentinelese population arising from the 2004 Indian Ocean earthquake and resulting tsunami is not known, other than the confirmation obtained that they had survived the immediate aftermath.[7]