Mammals are vertebrates – animals that have a backbone. This means that all mammals have a bony skeleton inside their bodies, which gives them a strong frame. They usually have two pairs of limbs, and organs such as a heart, lungs, stomach and intestine. They come in all shapes and sizes and live in a huge variety of places, from the frozen Arctic wasres to the hottest deserts on Earth.

Of all the different types of animals, mammals are the ones that humans can relate most closely to. This is because humans are just one of the many species of mammals. So what are their characteristics? How are they alike and what are their differences?

They Produce Milk

All mammals have mammary glands, which are used to provide milk for their young. Mammary glands are made up of glandular tissue and ducts and develop from the sweat glands. While many have nipples that allow their young to nurse, one family of mammals, known as monotremes, secrete milk through ducts rather than nipples.

In nearly all mammals, the female is the only one who feeds the young. This means that the nipples of the male, while present, are underdeveloped. In a few species of mammals, such as the Bismarck masked flying fox and Dayak fruit bat, both the male and female are capable of producing milk and both will help care for the young.

They Are Warm-Blooded

A warm-blooded animal is better able to regulate its internal temperature, making it more resilient to outside threats. While a cold-blooded reptile requires a certain external temperature to function, warm-blooded mammals can maintain their body temperature through diet and other methods.

They Have a Four-Chambered Heart

One characteristic of mammals that you cannot see is their four-chambered heart. Reptiles and amphibians have three-chambered hearts, while fish have hearts with two chambers. Birds and mammals are the two classifications of vertebrates that have four chambers.

With a four-chambered heart, the body can easily keep the deoxygenated blood heading to the lungs separate from the oxygen-rich blood heading away from the lungs. This means the animal has fully oxygenated blood available at all times. By having constant access to a well-oxygenated supply of blood, mammals are able to physically exert themselves more fully and without the need for frequent breaks.

Most Replace Their Teeth Once Over Their Lifetime

With the exception of a few mammals, such as kangaroos and manatees, mammals replace their teeth once over their lifetime. Born with deciduous teeth, these fall out to make room for the primary teeth. If they lose a primary tooth, it doesn’t grow back. This contrasts with animals such as alligators and sharks, that can replace teeth throughout their life.

Their Lower Jaw is Made of a Single Bone

In other classes of vertebrates, the lower jaw is made up of several bones and is not attached to the skull. The mammal’s jaw is made of a single bone, attached to the skull. This solid structure gives the mammal’s jaw tremendous power.

They are Protected by Hair

All mammals have some form of hair or fur during some period of their life. Some, like dogs and cats, are covered in fur throughout their life. Others, such as dolphins, have a light covering of hair early in development.

Hair can provide camouflage, protection from the weather, and aid in exploring their environment.

Credit : A-Z Animals 

Picture Credit : Google


The largest of all the turtles is the leatherback, which can grow up to 1.6 m long and weigh about 360 kg - almost as heavy as a horse. Unlike other turtles, its shell is not hard but slightly flexible with an almost rubber-like feel. It can stay underwater for over an hour and dive to a depth of about 1280 m.

The leatherback sea turtle is the most unique of all sea turtle species. As the only living member of the family Dermochelyidea, they are the largest living turtle species and have the greatest migratory distribution of any reptile on the planet. Its distinguishing feature is its carapace, which has a smooth, leathery skin that covers a flexible matrix of bone. This carapace is highly specialized for diving to extreme depths of up to 4,000 feet (1,219 meters). In addition, a unique thermoregulatory adaptation allows leatherbacks to maintain core body temperatures at these extremely cold depths.

Adult leatherbacks have few natural predators, but their eggs and newborns are preyed upon by many animals, including birds, raccoons, and crabs. Female leatherbacks tend to return to the same nesting area to lay their eggs. Their large size makes them opportunistic in selecting a nesting beach. Like most reptiles, temperature determines the gender of the offspring—if it’s warm inside the nest, females will be born. Likewise, if temperatures are cooler, males develop. Once the eggs hatch, they’re on their own—the baby sea turtles must make it into the water and learn to fend for themselves without any care from their parents. Leatherbacks reach maturity at approximately 16 years old. Their average lifespan is unknown, but it’s thought to be at least 30 years.

Leatherbacks are found in tropical and temperate marine waters all over the world. They live off both the east and west coasts of the United States, and also in Puerto Rico, the Virgin Islands, and Hawaii. Leatherbacks spend most of their lives at sea and sometimes look for prey in coastal waters.

Jellyfish make up the biggest portion of their diet, but they also eat seaweed, fish, crustaceans, and other marine invertebrates. Leatherbacks have downward-pointing spines in their throat, which allows jellyfish to be swallowed, but prevents them from coming back up.

Credit : The National Wildlife Federation

Picture Credit : Google 


The hawksbill gets its name because its mouth resembles the sharp beak of a hawk. The turtle, which has a beautifully coloured and patterned shell, lives among the coral reefs of the Pacific, Indian and Atlantic Oceans. It can grow to about 1.14 m, more than half the length of a full-size bed, and weigh almost 70 kg.

Hawksbill turtles often nest in small numbers, and usually on remote beaches. The largest populations of hawksbills are found in the west Atlantic (Caribbean), Indian, and Indo-Pacific Oceans.

The largest nesting populations of hawksbill turtles occur in Australia and Solomon Islands. Approximately 2,000 hawksbills nest annually on the northwest coast of Australia and 6,000 to 8,000 nest annually in the vicinity of the Great Barrier Reef. The largest rookery for hawksbill turtles in the South Pacific Ocean is in the Arnavon Islands of the Solomon Islands, where approximately 2,000 hawksbill nest each year. Arnavon hawksbills have been heavily exploited for their shell for centuries, but two decades of conservation and monitoring efforts are showing encouraging signs of recovery. Around 2,000 hawksbills nest each year in Indonesia and 1,000 in the Republic of Seychelles. 

In the Atlantic, the greatest number of hawksbill nests are laid in Mexico, Cuba, and Barbados, but nesting occurs throughout the Insular Caribbean. The most significant nesting within the United States occurs in Puerto Rico and the U.S. Virgin Islands. Each year, about 500 to 1,000 hawksbill nests are laid on Mona Island, Puerto Rico and another 100 to 150 nests on Buck Island Reef National Monument off St. Croix. In the continental United States, nesting is rare and is restricted primarily to the southeast coast of Florida and the Florida Keys. 

In the U.S. Pacific, hawksbills nest primarily in Hawaii where 10 to 25 females nest annually on beaches along the south coast of the island of Hawaii and the east coast of the island of Molokai. This population may constitute one of the smallest hawksbill nesting populations in the world, but is the largest in the Central North Pacific Ocean. In the Eastern Pacific, approximately 700 females nest annually from Mexico to Peru.

Credit : National oceanic and atmospheric administration

Picture Credit : Google 


This native of South Africa not only closes its hinged shell after pulling its head inside, it also releases a foul smell from its musk glands to keep predators away.

Cool Facts About The Hinged Terrapin

  • The Serrated Hinged Terrapin is the largest of the hinged terrapins.  They can grow between 30 and 50cm in length where females are usually larger than males
  • Found throughout tropical East Africa, the Serrated Hinged Terrapin is one of the most common hinged terrapin species.
  • Not selective about basking locations, the Terrapins lounge mostly on logs and rocks, but they also been found hitching rides on the backs of hippopotamuses!
  • Serrated Hinged Terrapins are so named because they have a hinge in their shell that they are able to close after pulling their head and front legs inward.

Hide ‘n’ Seek

Serrated Hinged Terrapins are carnivores that feed on a variety of creatures, including snails, mollusks, insects, frogs, and fish.  They will also consume carrion if available and have been known to eat ticks and parasites off of wallowing water buffalo.  Occasionally, they may also eat fruit. They may look cute and cuddly (for a amphibian) but you need to be careful of their incredibly sharp claws, which come in handing for hunting and defending against predator attacks. Typically they will only use this defensive strategy when hiding in the shell doesn’t seem to be working. These interesting creatures need to be on the lookout for numerous predators. During their lifetime, the Terrapins are preyed upon by crocodiles, monitor lizards, and the mongoose.

Long Walk To Water

Serrated Hinged Terrapins lay their eggs between October and January near water although they can sometimes be as far away as 500m.  The female will deposit between 7 and 25 eggs by burying them as deep into the ground as possible.  Burying the eggs not only protects them from predators but also prevents the eggs from drying out in the sun.   Hatchlings will appear between March and April and grow rapidly.

Stable and Happy

Luckily, with a widespread range and a stable population trend, the Serrated Hinged Terrapins are abundant and not listed as protected by any agency.  Although they are sometimes caught by fisherman and consumed by various peoples, overall, human activity has not harmed the population. It is always nice to hear that a population is doing well, so I always try to share these stories (I just wished it occurred more frequently).

Credit : Google 

Picture Credit : Google 


Female turtles lay their eggs in holes they dig on sandy beaches and then return to the sea. The eggs hatch in about 60 days, usually at night to give the tiny babies the best chance to avoid predators as they scurry down the beach and into the sea.

Sea turtles hatch throughout the year but mostly in summer.

Hatchlings use a carbuncle (temporary egg tooth) to help break open the shell.

After hatching, the young turtles may take 3 to 7 days to dig their way to the surface.

Hatchlings usually wait until night to emerge from the nest. Emerging at night reduces exposure to daytime predators. Studies have shown that some nests will produce hatchlings on more than one night.

For most sea turtle species, undisturbed nests can have more than 90% of the clutch successfully hatch. Nests disturbed by humans or animal predators tend to have a 25% or even much lower success rate.

Reaching the ocean

There are several theories as to how hatchlings find the sea.

  • Hatchlings may discriminate light intensities and head for the greater light intensity of the open horizon.
  • During the crawl to the sea, the hatchling may set an internal magnetic compass, which it uses for navigation away from the beach.

When a hatchling reaches the surf, it dives into a wave and rides the undertow out to sea.

  • A "swim frenzy" of continuous swimming takes place for about 24 to 48 hours after the hatchling enters the water.
  • This frantic activity gets the young turtle into deeper water, where it is less vulnerable to predators.
  • There have been reports of swimming hatchlings diving straight down when birds and even airplanes appear overhead. This diving behavior may be a behavioral adaptation for avoiding predation by birds. 
  • Past the surf zone, hatchlings use their internal magnetic compass for orientation.

The"lost" years.

After entering the ocean, the hatchlings of many species of sea turtles are rarely seen for 1 to 3 years. These are referred to as the “lost years.”

Researchers generally agree that most hatchlings spend their first few years living an oceanic existence before appearing in coastal areas. Although the migratory patterns of the young turtles during the first year has long been a puzzle, most researchers believe that they ride prevailing surface currents, situating themselves in floating seaweed where they are can find food.

Research suggests that flatback hatchlings do not go through an oceanic phase. Evidence shows that the young turtles remain inshore following the initial swim frenzy. Most remain within 15 km (9.3 miles) of land.

Credit : Sea world parks & entertainments 

Picture Credit : Google