Monday 2 November 2015

Mammals 101

Some of you may know that I at one time I was a science teacher - I was a paid member of that honourable profession for over 15 years.

My posts about echidnas seems to have generated both interest and confusion - so I will try to sort this out!

Mammals are a very familiar group of animals - many of our domesticated animals are mammals.  All mammals have fur (or hair), produce milk and are 'warm blooded'.  However, mammals are split into 3 groups based (more or less) on the way they reproduce.

The largest of these three groups are the placental mammals - these mammals are probably the most familiar of the mammals, and in most parts of the world they are basically the only mammals to be seen.  The young of this type of mammal undergo a reasonable period of development inside the female and are nourished through a placenta.  This type of mammal includes cows, cats, dogs, bats, seals, deer, whales and us.  It also includes hedgehogs and porcupines.  I'm a bit short of pictures of this sort of mammals, as I live in the only part of the world where they are not the dominant type of mammals.  So - here are a few placental mammals.

Domestic cat


Grey Seal

Humans (red-headed form!)
You can see that although all these mammals have fur or hair - the degree of furriness varies a lot between species!  (And not all mammals have red hair either!).

The next group of mammals are marsupials - with very few exceptions marsupials occur in the Australian region.  Opossums in America are a well known exception.  These mammals give birth to tiny, underdeveloped young that continue to grow in a pouch after they have been born.  Here are some marsupials.

Marsupials are a very diverse group - there are carnivores, omnivores and herbivores.  In the not too distant past there were marsupials the size of small cars and ones that were similar in behaviour to lions and wolves - living in Australia today is probably a lot less risky then when these mega marsupials were alive.

The final group are the monotremes.  These are egg laying mammals.  Once the egg hatches the young animal continues its development in a pouch.  The platypus is probably the best know monotremes,  but there are also two species of echidna - only one of which, the short beaked echidna, lives in Australia.  The other species of echidna is found in Papua New Guinea.

Short beaked Echidna
So, thats a quick tour through mammals - and the final point I'd like to leave you with is this - we, as humans, are more closely related to hedgehogs and porcupines that echidnas!  The fact that echidnas, hedgehogs and porcupines all have spines does not mean that they are closely related - although they probably all have them for similar reasons.

Hope you did not mind a quick burst of biology - once a teacher, always a teacher - just to show how unusual the echidna really is!


  1. Hello, Stewart

    I enjoyed your Mammal post and the images. happy Monday, enjoy your new week!

  2. That was great....loved my little lesson..... of course, here in Canada...we have only the porcupine variety.... no Echidnas.... they'd probably freeze to death..... our winters get to minus 40C .... today is our first snow of the season... although, it is only -5C today .... but,'s coming.
    I wish my poor limpy crow would go south ..even if he can only make it a few hundred miles it would be better.... if he stays, I will try to feed him...but, he'll have to fight with dozens of savvy magpies ...poor guy.

  3. This human is also the red headed form :-) Diane

  4. I knew this stuff but could not have explained it so succinctly and well. The mark of a great teacher.

  5. Still a science teacher! Thanks for the refresher. Enjoy your week.

  6. Still a science teacher! Thanks for the refresher. Enjoy your week.

  7. Brilliant post and well explained and wellillustrated with greast images Stewart.

  8. Thanks for the well done biology lesson.

  9. Brilliant pictures and enjoyable post Stewart. Your kids are very cute.

  10. Thanks for the refresher, Stewart, although I can't decide if those "red headed" ones even know that they are now used as examples...LOL! Oh, one more thing...learning never ends, "teach."...:)JP

  11. Well done teach! Now do one on reptiles that have live born babies.

  12. Hello Stewart!:)Many thanks for this lesson which was so well explained and illustrated.Good job!:)

  13. Very interesting!
    Hope you are having a wonderful day!

  14. You live and learn ! - and then you get old and forget!

    Enjoyed this one imensely, Stewart!

    Greetings from a cold and misty-damp UK - - - Richard

  15. I'm always open to learning new things. Believe me, Echidnas are new to me!

  16. Oh I loved this post! I want to show it to my grandson...he is very much "into" animals of all kinds. Thank you for clarifying the subspecies of mammals for me!