On Friday I gave you two pictures of a specimen from the Horniman Museum and asked you what it was:

Some good answers popped up but three of you managed to identify it as a howler monkey – so well done to Jim, SmallCasserole and Jake! It is indeed a howler – a Venezuelan red howler (Alouatta seniculus) to be more precise (N.B. it’s actually from Brazil, not Venezuela but most wildlife has little respect for human boundaries or classification).

The robust mandible on this specimen hides the most characteristic feature of a howler monkey – the hugely enlarged hyoid bone in the throat:

This bone acts as a resonating chamber that amplifies sound, making howler monkeys amoung the loudest (if not the loudest) terrestrial animals, with a call that can be heard for about three miles (guess where they got the name “howlers”…). This is a useful mechanism for communicating over long distances in rainforests, where visual and scent cues are easily missed by the complexity of the canopy. This is handy for keeping groups together and warning other groups off.

I’ll see if I can get away from bones for the next mystery object!