Nov 19
You can already find ARKive on Facebook, Twitter and Tumblr and now you can find us on Google+ as well!
If you are already part of Google+, you may have noticed the +1 icons on each species pages – you can now pick your favourite pages on ARKive and share them.

As Google has decided to work in circles, we decided to put together a collection of some of the best circles in nature.

Vicious circle

Circles make strong defensive positions, leaving no individual exposed. Take this characteristic muskox behaviour – the herd huddles together, encircling vulnerable calves inside a protective wall of adult bulk and sharp horns. These young are certainly no easy target for a hungry wolf, bear or any other predator.

Photo of muskoxen in defensive circle

Muskoxen in defensive circle

Fairy rings

A ‘fairy ring’ is a naturally occurring circle of mushrooms. The visible part of this mushroom is the fruiting bodies, arising from a singular spore in the centre. They are also places where elves gather to dance, apparently!

Photo of field mushroom ring

Field mushroom ring

 

Water circles

The humpback whale fluke print – a perfect circle of calm in a choppy ocean. As the humpback dives, it arches its back (hence humpback), raising its tail above the water. This print is all that’s left on the surface. Top marks for this dive.

Humpback whale fluke print, photo

Humpback whale fluke print

 

Rear rings

It’s obvious where this subspecies gains its name – the Ellipsen waterbuck (Kobus ellipsiprymnus ellipsiprymnus) is easily identified by the broad, white ring encircling its rump.

Ellipsen waterbuck with characteristic white ring on rump

Ellipsen waterbuck with characteristic white ring on rump

 

Circles of ages

Perhaps the most famous example of circles in nature – the rings of a tree trunk. New rings of cells are laid down annually, meaning it’s possible to work out how old the tree is. Unfortunately this means telling the age of a tree involves cutting it down.

Scots pine close-up of cut log, showing growth rings

Scots pine close-up of cut log, showing growth rings

 

Hygiene circles

Birds are great at keeping the nest immaculately clean, and this leads us to our next natural circle: a circle of guano. Marking the edge of this blue-footed booby’s nest, this is one circle I wouldn’t want to join…

Blue-footed booby incubating eggs on nest, surrounded by ring of guano

Blue-footed booby incubating eggs on nest, surrounded by ring of guano

 

Cold circles

Hidden in the coldest and driest continent on earth is a fantastic landscape of ice. About 99% of Antarctica is covered by an ice sheet, reaching over 4 kilometres thick in some places. Making our list of natural circles is this eroded iceberg – stunning!

Eroded iceberg at Cape Hallett, Antarctica

Eroded iceberg at Cape Hallett, Antarctica

 

So if you’re on +Google, come and join +ARKives circle where you can learn all about our new App, get updates from the blog and see what the team are up to.

 Lauren Pascoe, ARKive Media Researcher

  • Luckyrat (November 24th, 2011 at 4:57 pm):

    Do you really need to cut down the tree?

    Can’t electromagnetic waves of some description read the number of circles without needing to pierce the bark?

  • Lauren (November 25th, 2011 at 1:23 pm):

    Good point Luckyrat – you don’t always have to cut the tree down to determine its age! Techniques using MRI (magnetic resonance imaging) could be used to tell the age of a tree, although a cheaper and easier method is to use an increment borer – a hollow drill that takes out a small core of wood, so the rings can still be counted! Lauren