Juliana’s Golden Mole (Neamblysomus julianae) Photo by Craig R. Jackson (DOI: https://doi.org/10.11647/OBP.0177

Dear Readers, for some time now we’ve known that some mammals have iridescent fur – in particular the golden moles of Sub-Saharan Africa glint most attractively, These unusual mammals are blind and deaf to airborne sound, but have very well-developed organs in their ears for picking up seismic vibration – as they spend most of their time underground, this is a useful adaptation. But why is their fur iridescent?

A recent study by scientist Jessica Leigh Dobson at Ghent University has picked up iridescence in the fur of a further 14 mammal species, including 10 rodents and the otter shrew (neither an otter nor a shrew). All showed glints of green or purple in their fur when viewed from a certain angle – this effect is seen most commonly in birds such as hummingbirds, and a number of insect species.

Even a common species such as the Vlei Rat turns out to shimmer – you can see an image of the fur here.

But why? The jury is out, but the commonest explanation is that the iridescence is a side-effect of the smoothing of the cuticle of each individual hair. All of the mammals found with this phenomenon so far either live in the soil, or spend a lot of time in water – they theory is that the smoother hairs help the animal to travel through their chosen medium more easily, and that the structure also helps to keep the fur clean.

Some have suggested that the iridescence could be used for communication, as it definitely is with male hummingbirds, who display the changing colours of their feathers to attract mates and to scare off rivals.

Anna’s Hummingbird (Photo by James Marvin at https://www.flickr.com/photos/mandj98/54172229556/)

However, I find this less convincing, when you think that the golden moles can’t see, and they are the group with the widest range of iridescence. However, many of the mammal species with iridescent fur so far discovered can see, and as Dobson points out, there are 2500 rodent species, and only a handful have so far been assessed for iridescence. It will be interesting to see if more species are found, and what conclusions are reached. In the meantime, it appears that even the humblest of mammals are turning out to have a whole range of new characteristics.