The Galapagos penguin ( _Spheniscus mendiculus_ ) is the only penguin species found north of the equator, thriving in the equatorial waters of the Galapagos Islands. This distinctive habitat, influenced by cool ocean currents, plays a role in the species’ survival. The availability of food in these marine environments directly impacts the penguins’ ability to reproduce and maintain their populations.
Main Food Sources
The primary diet of the Galapagos penguin consists of small, schooling fish species, including anchovies, sardines, and mullet. These are abundant in the cold, nutrient-rich waters around the archipelago due to the upwelling of deep, cool water that brings vital nutrients to the surface. The abundance of these fish is linked to the marine ecosystem’s productivity, fueled by phytoplankton, which form the base of the food chain. While fish make up the bulk of their diet, Galapagos penguins also occasionally feed on small crustaceans. Their size and schooling behavior make these prey efficient targets for the penguins’ hunting strategies.
Hunting Methods
Galapagos penguins exhibit highly agile swimming abilities, central to their hunting success. They can reach speeds of up to 35 kilometers per hour underwater, pursuing fast-moving prey. Their streamlined bodies and powerful flippers propel them efficiently, making them effective pursuit divers. While capable of diving to 27 meters, most foraging dives occur within five meters of the shoreline and last less than one minute.
These penguins are visual predators, relying on keen eyesight to spot prey during daylight hours. A clear protective membrane covers their eyes, shielding them from saltwater irritation underwater. They often employ a pursuit-diving technique, diving beneath schools of fish and catching them as they rise to the surface. This method can also inadvertently herd fish closer to the surface, creating feeding opportunities for other seabirds. Galapagos penguins typically forage individually or in pairs.
Environmental Factors Affecting Diet
The availability of food for Galapagos penguins is significantly influenced by ocean currents and climatic events. The cold, nutrient-rich Humboldt and Cromwell currents are crucial for maintaining the high productivity of the waters around the Galapagos Islands. The Humboldt Current brings cold water from Antarctica, while the Cromwell Current, an underwater current, brings cool, nutrient-rich water to the surface through upwelling. These currents create an environment where small fish thrive, providing a consistent food source.
However, El Niño Southern Oscillation (ENSO) events can disrupt this delicate balance. During El Niño, ocean surface temperatures rise, and the strength of these cold-water currents diminishes. This reduction in cold, nutrient-rich upwelling leads to a sharp decline in phytoplankton and a scarcity of the small fish that constitute the penguins’ diet. Periods of severe food scarcity can force penguins to forgo breeding and lead to significant population declines due to starvation. For instance, strong El Niño events in 1982-83 and 1997-98 resulted in population drops of 77% and 65%, respectively.