Saturday, 12 September 2015

Colours in Nature; orange - other vertebrates

In the last posting we talked about orange in animals, focussing on birds. I raised there the problems of precisely defining orange, and I think that becomes even trickier in mammals. For instance by what colours would you define this antelope and tiger?
Impala Aepyceros melampus, Lake Mburo NP, Uganda

Sumatran Tiger Panthera tigris sumatrae, Adelaide Zoo
(and how I wish I could tell you I'd photographed it in Sumatra!)
I think that both could arguably be described as orange (indeed Wikipedia uses a tiger to illustrate its article on orange) though I'd probably think of them as rusty red/chestnut and will deal with this shade thus in a future posting. 

An important difference between orange pigment in birds and in most other animals is in the nature of the pigments themselves. For instance while mammals certainly absorb carotenoids from their food and metabolise them, few if any mammals use them for colouration. Instead yellows and oranges and rusty tones in mammals (including in red-haired humans) are due to a class of melanins (normally thought of as brown or black) called pheomelanins. These can be synthesised in the body, unlike carotenoids. 

When I started looking into it, I discovered that most of the mammals I'd call orange - as opposed to chestnut etc - are primates. The most obvious of these are Orangutans. (And of course the name comes from Malay, and has nothing to do with 'orange'.)
Bornean Orangutan Pongo pygmaeus, with baby, Sepilok, Sabah.
Venezuelan Red Howler Monkeys Alouatta seniculus, Manu NP, Peruvian Amazonia.
Despite the name, this is the common red howler of the western Amazon; three species are now recognised.
Red Leaf Monkey Presbytis rubicunda, Gomantong Caves, Sabah.
This beautiful monkey is restricted to Borneo and nearby islands.
Golden-mantled Tamarin Saguinus tripartitus, Napo Lodge, Yasuní NP, Ecuadorian Amazon.
And maybe that is really gold rather than orange, but I'm not entirely convinced...
This lovely little monkey also has a limited range, in Ecuador and north-eastern Peru,
and Napo Lodge is probably the best place to see it.
Primates don't have the orange mammal certification entirely to themselves though.
Northern Amazon Red Squirrel Sciurus igniventris, Yasuní NP, Ecuador.
In other vertebrates the story is different again. The class of chemicals known as pterins was first described from (orange) butterfly wings, but they have since been discovered in a range of other groups, including reptiles and amphibians (and other invertebrate groups, but we'll visit them next time). Like melanins, but unlike carotenoids, they can be synthesised by animals. 
Poison Dart Frog Ameerega bilinguis, Yasuní NP, Ecuador.
(Do not ever try this; the hand belongs to an indigenous man who's been doing it all his life and
has developed an immunity to the frog's poisons.)
Cinnamon Frog Nyctixalus pictus, Batang Ai NP, Sarawak.
This is a climbing shrub frog of the family Rhacophoridae; and yes you've seen this picture
in a recent post, but it was integral to both that one and this...

Basking Land Iguana Conolophus subcristatus, North Seymour, Galápagos.
Like the frogs, this somnolent fellow almost certainly employs pterins to brighten himself up.
And there we'll leave if for today, returning soon (when I'll be preparing it 'live') to look at orange invertebrates.



Susan said...

For the first two animals I would switch to French if at all possible and describe them as fauve, a word that means basically 'wild animal colour'. It applies especially to big cats. The best English translation is 'tawny' although it is often translated as 'fawn', which I think is misleading.

Ian Fraser said...

Thanks Susan - that really does raise all sorts of fascinating questions about how different cultures see colour. (I'm pretty I read somewhere that in Russian what we'd call dark and light blue are regarded as different colours?) Your fauve fits the bill much more adequately than any English word I can find, though tawny is good!