Mammals rank high in the animal popularity contest for a variety of reasons: (1) we belong to the same group as them, (2) they are some of the most complex organisms on the planet (in terms of both anatomy and behavior), and (3) they are almost always at the top of every food chain they exist in. Here are five of the most popular mammals in the world.

Dogs

Photo by Jes Mahnke

• Considered to be man’s best friend, they are the world’s number one choice for a house pet. This is probably why they are the most popular mammals in the world. 
• They are believed to be direct descendants of gray wolves. 
• Apart from feral dogs and mixed breeds, there are currently 200 dog breeds recognized by the American Kennel Club (see the list here). If you want to get one for yourself, there is no shortage of options to choose from.
• Dogs are often kept as pets, service animals (for therapy or for helping the disabled), military and police assistants (sniffing drugs, bombs, living targets, and chasing after criminals or enemies), protection (guard dogs), or just for plain old companionship. 

Cats

Photo by Mustafa ezz

• House cats are almost as popular, if not more popular, than dogs (especially in some countries). 
• Their genetic sequence is more than 90% similar to the tiger, which is probably why they also share a lot of physical and behavioral traits with their bigger cousins in the jungle. 
• They have excellent peripheral and night vision, allowing them to hunt small critters at night – birds, mice, small insects, and reptiles.
• They can climb up trees easily but not down because their claws are all curved downward. The only way for them to get down from trees is if they jump or they learn to back down (hind legs first). 
• Unlike in the case of dogs where breeds are clear-cut and easier to distinguish, cats are harder to classify by breed. Estimates put 95% of domesticated cats as non-pedigreed. However, according to the Cat Fanciers’ Association (CFA), there are 45 recognized breeds in existence. Check the list here.

Bats

Photo by HitchHike

• They are the only mammals who have mastered true flight. 
• Their bodies have evolved drastically for flight, replacing forelimbs with featherless wings, and even shortening their hindlegs (which are now mostly used for hanging onto roosting areas).
• They use a sound-based strategy called echolocation to navigate through the obstacles in their flying space so they can fly safely even on pitch-black nights. 
• Some bats, like vampire bats, drink blood.
• They have a very active immune system which keeps them safe even in virus-infected colonies. Deadly viruses like the Ebola virus, Marburg virus, Nipah virus, Hendra virus, severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory coronavirus (MERS-CoV) and SARS-CoV-2 (which caused the COVID-19 pandemic), have been linked back to various bat species.

Whales

Photo by Elianne Dipp

• They are not just the biggest mammals on the planet, but they are also the biggest animals in the world.  
• These mammals are built for underwater life – forelimbs turned front flippers, huge rear-facing blowholes, rich myoglobin concentrations for higher Oxygen reserves in the muscles, enormous tails that provide energy-efficient propulsion, and a low surface area-to-volume ratio that allows it to retain body heat even in the most frigid marine conditions. 
• They regularly build up a huge fatty blubber for reserves, allowing them to survive for 4 straight months without eating (fasting). They then replenish their energy by feeding for the next 8 months and restoring their blubbers in preparation for the following months of fasting. 
• On average, they can stay underwater for 60 minutes. However, some species of whales like the Sperm Whale can hold their breath for 90 minutes. The longest record though is held by the Curved Beak Whale, staying underwater for 138 minutes on a single breath of air.
• They were born with hairs (sensory hairs) along their jaws and heads. They get shed off by most species after some time. 

Elephants

Photo by FUTURE KIIID

• They are the biggest animals on land. Even the baby elephant can weigh as much as 120 kg at birth. 
• Despite their size, they are very good swimmers.
• Their trunk (which is an extended nose fused with the elephant’s upper lip) can do so much more than just smell. It also functions as a hand (grasping, lifting, feeling, picking, squeezing, prying open stuff, and more), a snorkel, a vacuum cleaner, a water pump, a towline, a trumpet, and a communication device. 
• Their tusks, which are evolved overgrown teeth, are used for protection, digging, stripping tree barks, lifting objects, and competing with other elephants. They also fetch a high price in the market which is why poachers are still hunting down these animals despite government protection. They are also the main reason why these animals are now close to extinction.
• There are dedicated organizations to saving these endangered magnificent animals. You can visit some of them here (international) or here (Asian).

Frequently Asked Questions

How many types of elephants are there? 

Currently, there are 3 types of elephants around, two of them are from Africa – the African Forest Elephant and the African Savannah Elephant – while the last one is the Asian Elephant. Currently, African elephants have had great success in rehabilitation and repopulation after extensive conservation efforts. They are now back to half a million in the wild – considerably better but still vulnerable. However, the Asian elephant population continues to decline. Estimates suggest that there are only 40,000 – 50,000 of them left in the wild, putting them on the endangered species list. 

How many types of whales are there?

Based on gross morphology, people generally classify whales into two types – Baleen whales (those who filter food from the water using keratin-based bristles called baleen) and Toothed whales (those who chomp down on prey using teeth). Taxonomically speaking though, there are 90 different species of identified whales. 

Do bats bite humans?

No, at least not unprovoked. Bats generally avoid contact with other animals – humans or otherwise. However, when captured or handled, they can resort to biting as they try to free themselves or discourage you from getting closer. Even vampire bats, (who received such a bad rep from vampire movies) will rarely approach humans for a blood meal. Instead, these blood drinkers will often go for cattle, pigs, horses, or chickens. The biggest danger they pose is not turning you into vampires, but passing on viruses that they might be infected with (rabies, SARS, SARS-CoV-2, and possibly even more).