Kangaroos or roos as they are sometimes called, are members of the animal kingdom endemic to the continent of Australia.
They are found widespread from north to south, east to west and throughout the mainland part of Australia and are most notable for possessing extendable pouches in front of their abdomens which contain four squirting teats for suckling their joeys.
In this article, we’ll be discussing something rather bizarre about kangaroos, whether or not they are mammals. Keep reading to find out if you haven’t already.
What is a mammal?
Before we go straight into the answer of whether or not kangaroos are mammals, (which is stated clearly in the next section), it is very important that we know what mammals are so that we can easily relate as to why kangaroos are classified the way they are. So, what are mammals?
Mammals are simply members of the animal kingdom that belong to the class of animals known as ‘Mammalia’ — a term derived from the Latin word of “mamma” which translates into the English word for ‘breast’.
Mammals have a variety of autapomorphies or distinct features that can be used to identify them, but worth noting though, is that not all of these features are present in every member species.
Some may have them while other won’t, or will have them in a reduced or vestigial form. But all the same, these characteristic can only be pinpointed in members of the mammalian group and not in birds, reptiles, amphibians, fishes, or invertebrates that form the remaining five classes of the animal kingdom.
Some of the distinct characteristics or autapomorphies of mammals include:
- A neocortex region of the brain: The neocortex, neopallium or isocortex is a portion of the brain involved in higher order brain functions such as sensory perception (being able to respond to physical stimuli), cognition, generation of motor commands, spatial reasoning and language. This portion of the brain is a feature observed only in mammals.
- Mammary gland: Mammary gland is a modified apocrine sweat gland responsible for the production of milk which is used for feeding offspring. This feature and its function is majorly pronounced on the female species of mammals, although males can have non-milk producing mammary glands and sometimes even have a fully functional milk producing gland, thereby taking over the task of feeding their young ones after they are given birth to by the females; e.g the male Dayak fruit bat. The mammary glands can be located in breast for primates, udders for ruminants, and dug for other animals such as dogs and cats. The mammary gland can have nipples or teats for squirting out the milk to young, or lack them at all. So while all young derive sustenance from the mammary gland during the early stages after birth, not all of them are able to suckle milk. Some like primitive monotremes, lick or catch the milk using their tongue.
- Sweat glands: Sweat glands are tubular structures on the skin that produces sweat. Only mammals have these structures and some of these gland have been modified to form features like the mammary gland, ciliary glands and the ear wax producing ceruminous gland.
- Body hair: All mammals posses body hairs in at least one lifecycle stage of their lives. The hairs can be of various sorts and serve different purposes such as: whiskers for sensing, quills and horns for defense and thick coats for protection, insulation, camouflage and social signaling.
- Only mammals have a single bone in their lower jaw or mandible called the dentale. This bone articulates or fixes to the skull and allows for efficient and strong bite necessary for grinding, cutting and chewing.
- Only mammals have three bones in their middle ear.
- Only mammals have nostrils that open at a common stricture called nose. Some mammals like the cetaceans however, have nostrils that lack an external protective organ called the nose.
- Only mammals have large four chambered hearts with the left aorta being persistent. Birds have four chambered hearts, but their right aorta is persistent instead of left aorta.
- Only mammals have a muscular diaphragm.
- Only mammals have voice organ in the larynx with several pairs of membranous muscles.
- Only mammals have molar teeth.
- Only mammals can change teeth twice: from milk or deciduous teeth to permanent teeth.
Note: The features from above are only part of the numerous traits, characteristic and features that presents the fine line between mammals and other classes of animals.
Other prominent features also exist which are observed widespread amongst the majority of mammals, but these features are in no way unique to only mammals. Other classes of the animal kingdom from birds, amphibians, fish, reptiles and invertebrates may also have members that possess these features. Examples of such traits include.
- Both mammals and birds have a four chambered heart.
- Mammals and birds are endothermic and can be homeothermic as well.
- Many mammals have high metabolic rates and so do many species of birds.
- Most mammals walk on four legs similar to the way many species of reptiles do.
- Most mammals give birth to their young ones alive similar to the way some reptiles and even birds do.
- All mammals are vertebrates and so are birds and reptiles, fish and amphibians.
Are kangaroos mammals?
Yes, kangaroos are mammals because they fulfil all the necessary criteria required for an animal to be considered a mammal.
Kangaroos belong to Class; Mammalia, Order; Diprotodontia, Family; Macropodidae and Genus; Macropus.
Under this genus, four distinct species of kangaroos are extant which are distributed in huge numbers across the landmass of Australia.
Some of the features that justify the placement of kangaroos into the mammalian group includes:
- Kangaroos have short coarse body hair which can vary from soft light grey in the antelope kangaroos to blueish gray or a reddish tan as seen in the species of red kangaroos. The coat helps confer them camouflage and insulation.
- They have three middle ear bones.
- Kangaroos have a neocortex region of the brain.
- Kangaroos have a mammary gland with four teats for nurturing their young at different age groups. The mammary gland is built inside the pouch located on their abdominal area.
- Kangaroos are endothermic, homeothermic and have four chambered heart with the left aorta persistent.
- Kangaroos have molars, and have been observed to switch indelibly from deciduous to permanent teeth.
All these characteristics alongside the many many more that we’ve not mentioned above, helps scientist to comfortably classify kangaroos as mammals and not birds, reptiles or amphibians to mention but a few classes.
What type of mammals are kangaroos?
In the previous section, you learnt about the traits that justified the identification of kangaroos as mammals. In this section, we’ll be discussing exactly what type of mammals kangaroos are, because obviously, not all mammals are the same. It might be that obvious to you though.
Kangaroos belong to the marsupial clade of the mammalian class. This clade forms one of the three major clades or groups of the mammalian class, the other two being the placental mammals and the monotreme mammals. Let us briefly look at these group one after the other in order to fully understand what they mean.
What are marsupial mammals?
Marsupial mammals are mammals that give birth to their young ones at an underdeveloped state.
They have a relatively brief period of gestation or pregnancy compared to placental mammals and must nurture and protect their young in a pouch or a flap of skin on the surface of their body in order for the young to grow into a precocial one.
In kangaroos for example, mother gives birth to joey at around 32 to 36 days after mating with a male. That’s the equivalent of a human giving birth at around two months of pregnancy. As expected, the joeys birthed are in the early stages of fetal development and are not well equipped to survive the harshness of the Australia wilderness.
Kangaroo joeys as well as the joeys of all other marsupials, basically crawl out of their mothers underside at the expiration of their gestation period and work their way into her abdominally positioned pouch where they enter and immediately attach themselves to one of the four teats located within.
The teat selected instantly swells to fasten and keep the joey (which barely has enough energy to suckle on its own) in position. There and at that position, the blind, deaf and naked joey nurtures and grows into a fully furred and perceptive individual (while developing enough jaw muscles to unfasten itself at around one month of age to suckle at will).
Other animals that belong to the marsupial group include the koalas, tasmania devils, moles, wombats, opossums and potoroos.
What are placental mammals?
Placental mammals are mammals that give birth to a fully developed young after a relatively long period of gestation.
The young so born can be precocial (able to feed itself immediately after birth) or altricial (unable to feed itself immediately after birth), but have fully developed organs and external features after birth.
Placental mammals use a special organ called the placenta to supply nutrients, allow for waste exchange, and also provide immune protection to their developing embryo. The name of the group is derived from this special organ.
Marsupial mammals also develop a rudimentary type of placenta during the early stages of their embryo development, but because their systems have not evolved to prevent immune rejection of the young by the mother, the placenta is unable to protect the young and it therefore the embryo has to be expelled at the early stages of gestation in order to compete postnatal development in a secondary nursing home called the pouch.
Placental mammals include humans, monkey, lions, dogs, cats, cattle, horse, etc.
What are monotreme mammals?
Monotreme mammals are mammals that lay eggs. Yes, you heard that right! Monotremes lay eggs similar to reptiles and birds, although their eggs are more leathery, and the young so born still fasten to or depend on it mothers milk for sustenance, unlike in birds and reptiles.
Two species of monotremes exits today and they include the echidnas and the duck looking platypus.
Kangaroo taxonomic classification
- Domain = Eukarya.
- Kingdom = Animalia.
- Phylum = Chordata; Sub-phylum = Vertebrata).
- Class = Mammalia; Sub-class = Marsupialia.
- Order = Diprotodontia; Sub-order = Macropodiformes.
- Family = Macropodidae.
- Genus = Macropus.
- Species = Macropus rufus, Macropus bernarnus, Macropus fuliginosus, Macropus giganteus.
Four distinct species of kangaroos exist today and are found strictly and mostly occupying different regions within the Australian continent. The four species include:
- The red kangaroo (Macropus rufus)
- The Antilopine kangaroo (Macropus bernardus)
- The easter grey kangaroo (Macropus giganteus)
- The western grey kangaroo (Macropus fuliginosus)
More interesting articles
- Are kangaroos rodents?
- Baby Kangaroo: Everything you should know
- Inside of a kangaroo pouch: What does a kangaroo pouch look like?
Cite this Article ” (APA Format)
Bunu. M. (2020, July 25). Are kangaroos mammals?. Retrieved from http://emborawild.com/are-kangaroos-mammals/