The Galapagos sit on the equator, but the water around them is not tropical everywhere. The Cromwell and Humboldt current systems bring cold, nutrient-rich water to the western islands, supporting the schooling fish that penguins need. Fernandina and western Isabela hold most of the population, and some colonies lie north of the equatorial line.
Staying cool on land is the harder problem. The birds nest in shaded lava cracks and caves, pant to lose heat, hold their flippers out to shed warmth, and stand with their backs to the sun or shade their feet from it. Much of the day is spent in the water.
The population is small and volatile. Strong El Nino events warm the surrounding water, collapse the fish supply and have caused severe die-offs, with numbers roughly halving in the worst episodes before partial recovery. That sensitivity, more than direct human pressure, drives its endangered status.