The Galapagos penguin, Spheniscus mendiculus, is a unique species, distinct for being the only penguin found north of the equator. These small penguins, averaging 19 inches in length and 5.5 pounds in weight, are endemic to the Galapagos Islands of Ecuador. Despite their tropical habitat, they thrive due to the influence of cold ocean currents. The Galapagos penguin is currently classified as endangered, facing numerous challenges that threaten its survival in this isolated archipelago.
The Galapagos Penguin’s Unique Vulnerabilities
The Galapagos penguin possesses inherent characteristics and habitat specificities that make it particularly susceptible to environmental changes. Its limited geographical range within the Galapagos archipelago, with most of the population on Fernandina and Isabela Islands, makes the species vulnerable to localized environmental disturbances.
These penguins rely heavily on the cold, nutrient-rich Cromwell and Humboldt ocean currents for their primary food sources, including schooling fish and crustaceans. These currents provide necessary sustenance in their warm, tropical environment, allowing the penguins to hunt close to the shoreline. The relatively small population size, estimated at around 1,200 to 2,000 individuals, further amplifies its vulnerability, as smaller populations are generally less resilient to sudden environmental shifts or threats.
Impacts of a Changing Climate
Climate change is a significant factor in the endangerment of the Galapagos penguin. Rising sea temperatures disrupt the cold ocean currents upon which penguins depend for food. Warmer waters reduce nutrient-rich upwelling, diminishing phytoplankton, the base of the marine food web. This leads to a decline in the small fish and crustacean populations that form the bulk of the penguin’s diet.
Intensified El Niño Southern Oscillation (ENSO) events, characterized by warmer sea surface temperatures, further exacerbate food scarcity. Strong El Niño events have historically caused severe population declines, with events in 1982-83 and 1997-98 leading to drops of 77% and 65% respectively due to widespread starvation and reduced breeding success. During such periods of famine, penguins may skip breeding altogether to conserve energy.
Conversely, La Niña events, which bring cooler sea surface temperatures, are associated with population recovery and improved body conditions for the penguins. However, climate change is projected to increase the frequency and intensity of El Niño events, posing a continuous threat to the species’ recovery.
Direct Human-Caused Pressures
Beyond climate change, direct human activities contribute to the Galapagos penguin’s decline. Accidental bycatch in fishing nets, particularly gillnets, poses a direct threat to penguins as they can become entangled and drown. Although industrial fishing is banned within the Galapagos Marine Reserve, illegal use of gillnets by artisanal fisheries still occurs, and under-reporting of bycatch makes it difficult to quantify the full impact.
Competition for food resources with local fisheries also places additional strain on the penguin population. As human fishing activities target the same small schooling fish that penguins rely on, food availability for the penguins can decrease, especially during periods of environmental stress. Marine pollution, including oil spills and plastic debris, degrades their habitat and harms the penguins. Oil spills can coat feathers, impairing insulation and buoyancy, while plastic pollution, particularly microplastics, can enter the food web and accumulate in the penguins’ bodies, with studies showing Galapagos penguins have the highest levels of microplastics per biomass compared to other organisms in their food web.
Threats from Introduced Species and Disease
Introduced species, brought to the islands by human activity, present biological threats to the Galapagos penguin. Feral animals such as cats, dogs, and rats prey on penguin eggs, chicks, and even adult penguins. These invasive predators lack natural checks on their populations, allowing them to exert significant pressure on native wildlife.
The risk of disease transmission from introduced species or domestic animals to the vulnerable penguin population is also a serious concern. Galapagos penguins have a limited natural immunity to many pathogens, making them highly susceptible to diseases like avian malaria and Newcastle disease. The introduction of the Culex quinquefasciatus mosquito, a vector for avian malaria, in the 1980s, and the discovery of the Plasmodium blood parasite in penguins in 2009, highlight this ongoing threat.