Keystone species mussel population explodes uncontrollably, driving out most other species. These creatures need not be apex predators. Sea stars are prey for sharks, rays, and sea anemones. Sea otters are prey for orca. The jaguar, whose numbers in Central and South America have been classified as near threatened, acts as a keystone predator by its widely varied diet, helping to balance the mammalian jungle ecosystem with its consumption of 87 different species of prey. The lion is another keystone species. Keystone mutualists are organisms that participate in mutually beneficial interaction and the loss of which would have a profound impact upon
Barbary macaques in Gibraltar Barbary macaques in Gibraltar Originally from the Atlas mountains and the Rif mountains of Morocco, the Barbary macaque population in Gibraltar is the only wild monkey population on the European continent. Although most populations in Africa are experiencing declining populations due to hunting and deforestation, the population of Barbary monkeys in Gibraltar is increasing. Currently, some 300 animals in five troops occupy the Upper Rock area of the Gibraltar Nature Reserve, though they make occasional forays into the town. As they are a tailless species, they are also known locally as Barbary apes or rock apes, despite being monkeys ("Macaca