Maccabees beautiful Bag of bones from Colour It In, i think this is right, the high 
on bass sound like they could be guitar but it fits in so why not :)

riff 1:
G:-----14--13--16--13--14----|
D:--14-----------------------|
A:12-----12--12--12--12------|
E:---------------------------|

riff 2
G:---11------11----13-----|
D:-11------11----13-------|
A:9-------9----11---------|
E:------------------------|

riff 3:
G:21-21--18-18-------------|
D:------------21-21p19-----|
A:-------------------------|
E:-------------------------|

riff 4
G:-----------------|
D:--------------14-|
A:-12--------------|
E:-----------------|

and the basically cycles through these riffs, the 4th one being played during the verses 
other during the choruses
message me if you find mistakes enjoy!