Abstract

Patterns of species abundance distribution (SAD) are driven by a given species’ physiology and life history and environmental variables. Climate variability such as El Niño Southern Oscillations (ENSO) has impacted marine fauna populations in the southern Pacific Ocean, including the Humboldt Penguin Spheniscus humboldti. After reviewing manuscripts and reports and conducting fieldwork, we could identify 80 Humboldt Penguin breeding colonies, distributed from La Foca Island (05°12’S/81°12’W) in Peru to Metalqui Island (42°12’S/74°09’W) in Chile. However, the number of breeding colonies was reduced to 72 after surveys were conducted along northern Chile. At least three S. humboldti and S. magellanicus mixed species colonies were noted in the southern part of the Humboldt penguin range. The main breeding colony in Peru, Punta San Juan, shows an overall population size reduction of 51% (1980 to 2008), with important decreases during El Niño (EN) events. On the other hand, Chañaral Island has had a significant increase (89%), which could be a result of the combination of irruption from more northern populations and a past underestimation. The SAD does not follow an unimodal log-normal shaped model, and the shape of the latitudinal SAD changed significantly southward. This temporal change in the Humboldt Penguin spatial distribution is supported by: its pattern of long distance migration during ENSO, the reduced population genetic structure and long distance gene flow between colonies indicating the absence of philopatry, reduction of population size in the main colonies in Peru, and the increase of population size of colonies along northern Chile. The change in SAD might be due to interactions between consecutive El Niño events, human activities and climate change. Although, to completely elucidate this pattern, further studies in population genetics structure, the species physiology, and environment variables in space and time are required.