The Teeny-Tiniest Animals on Earth

Mammal: Bumblebee Bat

The world’s smallest mammal, as noted by Guinness World Records, is the Craseonycteris thonglongyai, commonly known as the bumblebee bat due to its size. This teeny animal is also known as Kitti’s hog-nosed bat, a name that pays homage to its snoutlike nose and the fact it was discovered in 1974 by zoologist Kitti Thonglongya. 

The body of the average bumblebee bat measures a mere 1.14 inches to 1.29 inches long, though it has a relatively long wingspan by comparison — between 5.1 and 5.7 inches. The bat weighs between 0.05 ounces and 0.07 ounces, which is less than the weight of a dime and comparable to two grains of rice. This also means bumblebee bats are 80 million times lighter than the largest mammal, the blue whale. The creature is native to caves along Thailand’s Khwae Noi river as well as to Myanmar. Given their small stature, bumblebee bats rely on a diet of even tinier creatures such as itty-bitty spiders and moths.

There’s an argument to be made that the tiniest mammal is actually the Etruscan shrew (Suncus etruscus), which Guinness considers the smallest mammal in terms of total mass (while the bumblebee bee bat is the smallest by body length). These creatures are native to parts of the Mediterranean and South Asia and are slightly longer than bumblebee bats, measuring an average of 1.4 to 2 inches. While the smallest bumblebee bat may weigh 0.0599 ounces, however, some Etruscan shrews have been measured at 0.0529 ounces — a relatively substantial difference, even if on a tiny scale.

Bird: Bee Hummingbird

The tiniest bird in the world is yet another creature with an apian nickname: the bee hummingbird. Also known by its scientific name Mellisuga helenae, this airborne critter is native to Cuba and the nearby Isla de la Juventud (Isle of Youth). Bee hummingbirds measure around 2.24 inches long, and more than half that length is composed of the bird’s bill and tail. Females are slightly larger than males, though both are infinitesimally small at an average weight of just 0.056 ounces. According to the Audubon Society, these petite birds are roughly half the weight of a standard hummingbird.

Despite their small size, bee hummingbirds work hard and fast, with wings that beat 80 times every second. (That number increases to 200 times per second during courtship flights, which are performed to attract mates.) You can tell a male bee hummingbird from its bright red throat, whereas females have more of a bluish-green and gray coloring. If you ever happen to be birdwatching in Cuba, keep an eye out for bee hummingbirds in rainforests, mountain valleys, and rural gardens — essentially anywhere there’s nectar for them to feed on.

Fish: Spinyhead Seadevil

It may not be a trophy fish, but the Spinyhead Seadevil (Photocorynus spiniceps) holds the Guinness record for the world’s smallest fish. A relative of the anglerfish, this compact creature has an average length of just 0.24 inches, while the female is substantially larger at 1.8 inches, according to research conducted by Professor Theodore W. Pietsch of the University of Washington. Pietsch collected samples from the Philippine Sea, where the creatures live at a depth of around 4,675 feet.

That said, there’s some debate over how fish should be measured, and some newly discovered species have been deemed worthy competitors for the title of smallest fish. When it comes to female fish specifically, the record may go to Paedocypris progenetica, or the dwarf goby. Mature female dwarf gobies measure just 0.31 inches long and can be found in the swampy forests of Sumatra in Indonesia. 

Australian scientists William Watson and H.J. Walker Jr. posit another theory, claiming the world’s smallest fish may actually be the stout floater (Schindleria brevipinguis). In studying these fish, which are native to the Great Barrier Reef, Watson and Walker found the females measure around 0.27 inches long and males around 0.25 inches long. But the researchers also believe we should take weight into account when determining the tiniest fish. They suggest that stout floaters are more slender than the Spinyhead Seadevil and the dwarf goby and are therefore likely to weigh less than both species, though they lack conclusive evidence.

Reptile: Nano-Chameleon

Of the roughly 11,500 known species of reptile — a number that continues to climb — the tiniest one of the bunch resides on the African island nation of Madagascar. This small reptile is a dwarf chameleon known by the scientific name Brookesia nana, though it’s also referred to as the nano-chameleon. The discovery of this tiny creature was made in 2021 by a team of German researchers, who successfully collected two specimens: one male and one female. The team found the male to be much smaller, clocking in at a record-setting 0.53 inches from snout to vent, plus another 0.33 inches if you include its tail. However, as noted by Guinness, reptiles are typically measured sans tail, “as tail lengths can vary depending upon injury and other external factors.”

As this record was only confirmed in 2021, there may very well be other reptiles we’ve yet to discover that are even smaller. For now, the nano-chamelon reigns supreme, having taken the record from the 0.62-inch Jaragua dwarf gecko of the Caribbean. Unlike a stereotypical chameleon, Brookesia nana is incapable of changing color and always appears to be a shade of brown.

Amphibian: Brazilian Flea Toad

The name Brachycephalus pulex may sound like a towering dinosaur, but it’s actually a scientific name for the world’s smallest amphibian: the Brazilian flea toad. These little hoppers are native to the Serra Bonita mountain range along the Atlantic coast of Brazil and were first discovered in 2009. Ironically, the Brazilian flea toad isn’t a toad at all, but rather a frog. (They were initially believed to be toads, which accounts for the misnomer.)

It wasn’t until 2024 that scientists confirmed the record-setting size of these creatures, stripping the superlative from another frog, the Paedophryne amauensis of Papua New Guinea. Male Brazilian flea toads average 0.27 inches in length, though the smallest known example measured just 0.25 inches — smaller than a green pea or a housefly. Females are a bit larger, measuring 0.32 inches.

Invertebrate: Myxozoa

While the other five main animal groups are made up of vertebrates, invertebrates are frequently much smaller owing to their lack of skeleton. And it doesn’t get any tinier than myxozoans, which are the smallest animals of any kind.

Myxozoans are a class of animal considered to be obligate parasites, meaning they can’t survive without a host from which to get nutrients. Tens of thousands of these species are estimated to exist, and they’re often found in marine or freshwater environments. Of the thousands of myxozoan species that have been studied, Myxobolus shekel may be the smallest. Zoological professor Nicola Di Girolamo says this species grows to be no more than 8.5 micrometers, which is equivalent to 0.0003 inches. But most other species of myxozoa aren’t much bigger, generally reaching lengths between 10 and 20 micrometers (0.00039 to 0.00078 inches).