What is the rarest animal in the world? See the list of top 10 most endangered species.

Americans celebrated the 50th anniversary of the Endangered Species Act late last year, serving as a reminder of the 1,662 domestic and 638 foreign species it protects. The ESA is credited with saving 99% of listed species from extinction.

But, other species remain on the brink of extinction in the U.S. and around the globe. Heat, drought and rising seas brought on by climate change are threatening many species’ habitats. Rhinos, which are among the most endangered land animals, face near-unlivable climate change-related rising temperatures in southern Africa, a recent study found.

A black rhinoceros mother and her calf at Kruger National Park, South Africa. Climate change threatens both black and white rhinoceros populations in southern Africa, a research team at the University of Massachusetts Amherst concludes in a January 2024 study.

What is the rarest animal in the world?

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The vaquita is the rarest animal in the world and the rarest marine mammal. These porpoises swim in the Gulf of California and were only discovered in 1958, according to the World Wildlife Fund. They are on the brink of extinction in part because of the use of gillnets in illegal fishing operations, which often unintentionally trap marine mammals.

There are only about 10 vaquita remaining.

But there are still signs of hope – conservationists in northern Mexico spotted a vaquita calf swimming next to its mother in Sept. 2023, a promising sign of population growth.

Two species of rhinos are contenders for the title of rarest land mammal for different reasons. The Javan rhino is the “most threatened of the five rhino species” when it comes to poaching, according to the WWF. Only about 70 reside in the Ujung Kulon National Park in Java, Indonesia. But the Sumatran rhino, the wooly rhino’s closest living descendent, is threatened due to habitat loss. Remaining Sumatran rhinos live in “small, fragmented non-viable populations,” with low chances of finding each other to mate.

New study: Rising temperatures from climate change could threaten rhinos

What are the most endangered animals?

Here are the top 10 species in the “critically endangered” category based on population size estimates from the WWF:

Others on the critically endangered list include the African forest elephant, black rhinos, Bornean orangutans, eastern lowland gorillas, hawksbill turtles, Sumatran orangutans, Sumatran rhinos and western lowland gorillas.

What is the rarest fish in the world?

The Devils Hole pupfish are the rarest fish in the world. Last year, scientists counted just 175 of them swimming in a deep cavernous pool in the Death Valley National Park in Nevada. But the population has held steady in recent years, even reaching 236 during one fall count when food was more abundant. In 2013, there were only 35 fish.

These fish, who get their name from the way they “frolic about,” live an isolated life and share no common ancestry with any other species. They have one of the smallest, most distinctive habitats in the world, according to Smithsonian Magazine.

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This article originally appeared on USA TODAY: What is the rarest animal in the world? See the list of top 10 most endangered species.