Gentoos live in colonies with other gentoos, but are also known to live in colonies with other penguin species. Although the species all forage in the ocean, different species are partitioned to forage at different depths or distances. P. papau do not negatively affect other penguin species since they mainly forage right offshore.

Because gentoos live in large colonies with thousands of birds, flea and tick prevalence is high. Fleas from the genus Parapsyllus are common. The most prevalent tick is Ixodes uriae, which mainly affects the exposed skin of chicks such as ear canals, feet, and faces.

Cestodes, members of the genus Tetrabothrius, have been found in the intestines of Pygoscelis papau but little is known about their life cycle. The cestodes are found in various crustaceans that make up the gentoos' diet. Members of the genus Corynosoma also have been reported in gentoos.

Parorchites zederi, another species of cestode, latches onto the inside of gentoos' intestines. These parasites create small pouches in the intestines and insert their pseudoscoleces ("false heads") in them to feed. The areas that P. zederi latch onto increase in volume due to the creation of more intestinal cells and blood flow to the area increases.

Commensal/Parasitic Species:

• Intestinal parasites (Tetrabothrius pauliani)
• Intestinal parasites (Tetrabothrius wrighti)
• Fleas (Parapsyllus)
• Ticks (Ixodes uriae)
• Intestinal parasites (Parorchites zederi)
• Intestinal parasites (Corynosoma)