Q. I get different answers on the Internet when I ask what is the rarest animal in the world. What’s the correct answer?

A. In the strictest sense, the answer to your question could change daily. Counting insects alone, millions of species have gone extinct through the ages, and at a point before there were none, only one or two were left. You can’t get rarer than one. So for a time, each now extinct species was the rarest, or tied for the rarest, on earth.

Part of the problem in getting an unambiguous answer is the confusion between being rare, a numerical comparison, and being endangered, a human designation. Another complicating factor is that some people only consider vertebrates to be “animals.” Spiders, worms and snails don’t make the cut. One website I checked said that the vaquita, a small porpoise that lives in the Gulf of California, is the “rarest animal in the world.” It’s true that the vaquita is critically endangered and the poster child for how certain human endeavors threaten the survival of some of our planet’s incredible animals. But a few are still around, so calling it the rarest may be an overstatement.

Even fewer Red River giant softshell turtles exist. It may be the world’s largest freshwater turtle (over 260 pounds). A few years ago, conservationists knew of only three survivors. According to turtle biologist Jeff Lovich, “This is one of the rarest and most endangered turtles in the world. The last known captive female died in 2019, at a zoo in China. Another female living in the wild in Vietnam died in 2023. Overharvest for food by fishermen, dam construction, habitat destruction, and pollution have all contributed to the near elimination of this species.”

Another turtle was the rarest species on Earth at one time. A male tortoise named Lonesome George lived on Pinta Island in the Galapagos, achieving international significance as a symbol for turtle conservation as the only remaining member of its species. Although other species of the giant tortoises still survive on some of the Galapagos Islands, upon his death in 2012 that species became officially extinct. No species of animal on Earth could claim to be rarer than Lonesome George for several years.

Many animals reaching rarest-species-on-Earth status are large, charismatic or have achieved public recognition in some way. Martha, the last passenger pigeon, died in the Cincinnati Zoo on September 1, 1914. She was so famous that her carcass was frozen and sent to the Smithsonian to be stuffed and displayed in museum exhibits. The death of the last Carolina parakeet in the same zoo on February 21, 1918, was the end of another indisputably rare species.

When any species is down to its last few living individuals, questions arise about whether a few might still be alive in the wild somewhere. Some ornithologists still hope that ivory-billed woodpeckers persist in the Congaree Swamp in South Carolina or a forest in Cuba. The extinction of the Tasmanian tiger of Australia was not accepted for decades after the last one was presumed killed. Some Australians probably think a few still exist.

Rarity, even extinction, is a natural biological phenomenon. What is not natural is when we (human beings) are responsible for the rarity of a species because of our assaults on them directly or on their environment. It is time to take the ethical high ground in our proclaimed role as stewards of the Earth. I believe most people value Earth’s biodiversity and are ready to recognize the right of other species to inhabit the planet with us. Let us strive to ensure that causing any species to become rare because of habitat destruction, pollution or unsustainable removal from the wild becomes a rarity itself.

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