Despite sharing some key characteristics—such as warm bloodedness, milk production, and more—mammals can look and behave quite differently from one another. Their extreme differences are often a result of evolving in isolation in extreme environments. While their adaptations make them well suited to their habitats, they can also be quite susceptible to disturbances, including climate change and more.
Take a look at a few surprising modern mammals, learn more about the challenges they face, and discover what Field Museum scientists are doing to protect them!
When breeding populations become isolated, evolution can take some surprising turns. Striking examples of island evolution are the unusual mammals of Australia, Madagascar, and South America, each of which was isolated from the rest of the world for tens of millions of years.
Native to South America, spectacled bears are placentals—their babies develop for a long time inside the mother’s womb. But these bears have a unique adaptation: mothers can delay embryo implantation so that they give birth only when the food supply is abundant.
© AMNH/R. Mickens
While the vast majority of mammals are placentals—meaning their babies develop for a long time inside the mother’s womb—marsupials give birth to extremely immature young that continue to develop outside the womb in a pouch, a fold of skin, or attached to a nipple.
Many people refer to koalas as “bears,” but these marsupials are more closely related to kangaroos. Adult koalas are fairly large, but a newborn baby koala weighs less than 1/10th of an ounce (2 grams)—so small, it would easily fit in a teaspoon.
© AMNH/R. Mickens
Native to Tasmania and New Guinea, echidnas are mammals known as monotremes. Unlike most other mammals, monotremes never evolved live birth, but instead lay eggs like their earliest mammal ancestors.
Monotremes produce milk for their young, but they lack nipples; their milk oozes out of ducts in their mammary glands onto specialized patches of skin. When a nursing baby begins to grow spines, it leaves its mother’s pouch, but it comes back to nurse at her milk patches for several months.
© AMNH/D. Finnin
The last known Tasmanian “wolf” died in a zoo in 1936. Neither a species of wolf, nor a dog, it was the largest carnivorous marsupial in recent times. Its habitat, which once stretched throughout mainland Australia, was reduced to the island of Tasmania by the 19th century.
Humans believed that this nocturnal animal, sometimes called a “tiger” because of its stripes, preyed upon sheep and poultry (in fact, it preferred birds and small mammals), and hunted it intensively—the main reason the species became extinct.
© AMNH/J. Beckett
Hunting and habitat loss have contributed to the endangered status of proboscis monkeys, which live on the coasts and near rivers of Brunei, Malaysia, and Indonesia. The nose of the male can grow up to 7 inches (18 centimeters) and is believed to attract females.
During the past 500 years, at least 75 mammal species are known to have become extinct, with many more barely hanging on. Today, about 25 percent of living mammal species are threatened with extinction.
© AMNH/D. Finnin
While mammals are disappearing at an alarming rate, did you know that there are still undiscovered species around the globe? In the past 20 years alone, Field Museum researchers have identified 90 new living mammal species as well as 24 fossil mammal species.
In 2007, Dr. Lawrence Heaney and his team found this new species, which still awaits a name. The team has also helped to develop conservation plans that protect the unique ecology of the Philippines—one of the most severely deforested tropical countries in the world.
© The Field Museum/L. Heaney
Most insectivorous (insect-eating) bats like this yellow-winged species use ultrasonic signals called “echolocation calls” to locate and capture their prey. Dr. Bruce Patterson’s Bats of Kenya project uses bat calls to help identify bat species and document their crucial roles in nature and in controlling crop-eating insects.
By exploring, studying, and safeguarding habitats and species worldwide, Field Museum researchers are helping to understand and conserve the diversity of life on Earth.
© The Field Museum/B. Patterson