The Galapagos penguin ( _Spheniscus mendiculus_ ) is the sole penguin species found north of the equator. This places it in an unusual, warm environment for a bird typically associated with icy polar regions. Its presence in the Galapagos Islands highlights a remarkable adaptation to an unexpected tropical home.
The Unique Equatorial Habitat
The Galapagos penguin’s habitat is centered in the Galapagos Islands, mainly on Fernandina and Isabela. Two significant ocean currents make this improbable location possible. The cold Humboldt Current flows north from Antarctica, bringing cool waters.
The subsurface Cromwell Current further enhances this cold water, upwelling at the western Galapagos. These currents deliver cold, nutrient-rich waters to the surface, creating a marine environment abundant with prey despite the equatorial latitude. The upwelling supports high concentrations of phytoplankton, forming the base of the food chain for small fish like sardines, mullet, pilchards, and anchovies, primary food sources for the penguins.
Survival Strategies in a Warm Climate
Galapagos penguins adapt to their warm, equatorial environment. Their small size (40-50 cm, 1.6-2.5 kg) helps them dissipate heat more efficiently than larger penguin species. Bare skin patches around their eyes and beaks aid in heat radiation.
Behaviorally, they pant like dogs to cool down and stretch out their flippers to increase surface area for heat loss. During the hottest parts of the day, they seek shade in lava tunnels, caves, or rock crevices to avoid direct sun exposure. They also hunch over their feet to protect them from sunburn, as their feet have high blood flow and lack insulation. Foraging primarily occurs in the cooler waters of the Cromwell Current during the day, with penguins returning to land at night.
Life Among Other Species
Galapagos penguins occupy a specific niche in the marine food web. Their diet consists of small schooling fish (sardines, mullet, anchovies) and some crustaceans. They often hunt in groups, diving beneath fish schools and herding them towards the surface, providing feeding opportunities for other seabirds.
Aquatic predators like sharks, fur seals, and sea lions threaten adult and juvenile penguins. On land, their eggs and chicks are vulnerable to native predators like the Galapagos hawk, owls, and snakes. The Galapagos Islands are also home to other species that share or compete for resources, such as marine iguanas, blue-footed boobies, and frigatebirds.
Pressures on the Biome
The Galapagos penguin’s population faces various threats, with climate change being a primary concern. Increased frequency and intensity of El Niño Southern Oscillation (ENSO) events lead to warmer ocean temperatures and weakened trade winds, disrupting the upwelling of cold, nutrient-rich waters. This reduction in nutrients causes a decline in phytoplankton and fish populations, severely limiting the penguins’ food availability and increasing mortality rates, especially for chicks.
Other human-related pressures also impact the species. Ocean pollution, including plastic waste and oil spills, poses direct harm to penguins through entanglement or ingestion. Human disturbance from tourism can disrupt nesting sites, potentially leading to abandoned nests. Introduced species like rats, cats, and dogs prey on eggs, chicks, and even adult penguins. Introduced mosquitoes can also carry diseases like avian malaria, to which penguins may be susceptible.