Rock of Gibraltar may have originated from an escape of North African animals transported to Spain; it is also possible that the original Gibraltar macaques are a remnant of populations that are known to have spread throughout Southern Europe during the Pliocene, up to 5.5 million years ago. Some animals of the Rock have been reintroduced by the Alameda Wildlife Conservation Park who have three Barbary macaques. The Rock of Gibraltar, at the head of the Strait, is a prominent headland, which accumulates migrating birds during the passage periods. The vegetation on the Rock, unique in southern Iberia, provides a temporary home for
Gibraltar the overnight low is and the average sea temperature is . In the warmest month, August, the daily high temperature is , the overnight low is , and the average sea temperature is . Over 500 different species of flowering plants grow on the Rock. Gibraltar is the only place in Europe where the "Gibraltar candytuft" ("Iberis gibraltarica") is found growing in the wild; the plant is otherwise native to North Africa. It is the symbol of the Upper Rock nature reserve. Olive and pine trees are among the most common of those growing around the Rock. Most of the