Nēnē Research & Conservation


Feral cats in Hawaiʻi pose a major threat to native wildlife, including nēnē, through direct predation and the spread of the Toxoplasma gondii parasite. This parasite affects birds, mammals, and humans, with marine species like Hawaiian monk seals and spinner dolphins being particularly vulnerable. Toxoplasmosis, caused by the parasite, has led to numerous fatalities among monk seals, especially adult females, who are vital for the species’ recovery. Cats shed the parasite’s resilient oocytes in their feces, which can contaminate water sources and marine life. Understanding and addressing this issue is crucial for safeguarding Hawaiʻi’s delicate ecosystems and its unique, indigenous species.

What is Toxoplasma gondii?

Toxoplasma gondii is a parasitic organism that primarily infects cats and their relatives. When cats poop, they release oocysts, which are immature forms of the parasite. After 1-5 days in the environment, these oocysts sporulate, becoming infective. Domestic cats and their relatives are the only known definitive hosts for T. gondii. 

Why is T. gondii bad?

Toxoplasma gondii (T. gondii) poses a significant threat in the Hawaiian Islands, which have the highest per capita number of endangered birds in the USA, including species like the ‘Alalā, nene, red-footed booby, and Erckel’s francolin. This parasite, mainly spread through cat feces, has been linked to the deaths of these endangered birds and other native Hawaiian species such as spinner dolphins. Researchers from the University of Hawaiʻi found that T. gondii caused the deaths of two spinner dolphins, highlighting its lethal impact on diverse wildlife. Similarly, a study in the Journal of Wildlife Diseases indicated that T. gondii is the primary cause of death in nene, more than any other infection, with alarming infection rates across the islands.

T. gondii’s influence extends beyond its immediate lethal effects. It can alter the behavior of infected animals, increasing their vulnerability to dangers like predators or vehicles. For example, infected rodents display less fear of cats, boosting their predation risk. This behavior change benefits the parasite, as it requires cats for its life cycle. The widespread presence of T. gondii, its ability to infect various animals, and its environmental resilience pose a continuous threat to both animal and human health. This situation underscores the importance of managing feral cat populations and taking steps to prevent the spread of this parasite, which is crucial for protecting Hawaii’s unique wildlife and maintaining the health of its ecosystems.


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