Six-hundred meters west of the southernmost point is a shoal, Bajo Evelyn, which has a shallow depth of 8 fathoms.

When Hurricane Maria caused widespread destruction throughout Puerto Rico in September, 2017, tiny Cayo Santiago was also devastated.

About two-thirds of the vegetation on the island was killed, greatly reducing the shade available to the 1800 monkeys living there, who were in danger of heat related illness when exposed to direct sunlight on very hot days.

[6] The research paper published in the journal Science reported that "We leveraged 10 years of data collected on rhesus macaques before and after a category 4 hurricane caused persistent deforestation, exacerbating monkeys’ exposure to intense heat.

In response, macaques demonstrated persistently increased tolerance and decreased aggression toward other monkeys, facilitating access to scarce shade critical for thermoregulation.