Zoological Society of San Diego

The simplest solution? Take the pets out of nature!

Although the iguanas are the largest native vertebrate still alive today on the islands, when they're babies, their small size—maybe six to eight inches long—makes them vulnerable to introduced predators on the islands like cats, dogs, and mongooses. "You can go to certain islands in the Caribbean a month after the breeding season takes place, and you won’t be able to find a baby iguana; they're just all gone," Alberts laments.
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In the case of the 'Alala of Hawaii, the solution was more immediate and more drastic. These birds were part of a reintroduction program on the islands. A big problem for Hawaiian forest birds is becoming infected with malaria or pox viruses, thanks to mosquitos, which had been introduced to the islands in the 1880s. Many of the forest birds live at higher elevations, above the mosquito line, but not the crows. They were found to be able to survive pox and malaria infections, but the populations were still dying.

The team outfitted the birds with radio transmitters that came equipped with a mortality signal so that they could do post-mortem exams, which revealed that the birds had toxoplasmosis from Toxoplasma gondii. The disease vector was found to be feral cats—the crows would forage in the cats' feces, even treating the feces as a food item.

The solution here was to bring all the birds back into the captive breeding centers in order to beef up their numbers, and the plan is to reintroduce them to the wild once scientists can figure out a way to do so safely, without the birds being exposed to toxoplasmosis.