UV markings in Budgies, Gouldian Finches, Platypuses, Wombats, plus Lichens. © Don Burke.
Ultraviolet pigment and markings occur in many animals. When you put them under Black UV light they Glow. Why?
Recently, Platypuses, Wombats and other marsupials have been found to have UV pigment under black UV light. See New Scientist magazine 8th May 2021.
When I wrote my research article entitled ‘Ultraviolet Colours in Budgies’ in 2009, I put forward a theory as to what purpose these markings serve, which was that they are like Airport runway lights in a dark nesting hollow. They help mum & dad find the babies and vice versa. I wrote (in bold, below):
As any budgie breeder knows, budgies can’t see very well in low light conditions. Visit budgie aviaries in low light at dusk, when we can still see very well, and they will panic, flying into walls etc. So how do they find their babies to feed them in a dark nesting hollow?
Well it turns out that while budgies have poor vision in low light in general, they do have very good vision in low Ultraviolet light. All wild budgies have UV pigment on their cap (ie forehead) and a UV pigment stripe on their mask parallel to and next to each cheek patch (see photo). And so do their babies in the nesting hollow or box (see photo of a baby). This proves that budgies have good UV vision, whereas we have almost none.
Under black UV light, I photographed both adults and babies and found that they had similar facial UV pattern, with the adults having slightly more intense UV pigmentation and the babies a wider spread of UV (see baby photo above).
I also tested budgies in a very poorly lit room lit only by a very weak fluorescent light, and they couldn’t really see me at all, even though I could see well. Then I turned off the weak light and turned on a weak fluorescent UV Black light. Now I couldn’t see much, but the budgies could see my every move.
So parents presumably locate the circle and two broad areas of UV colour on each baby in the dark nesting hollow and feed it. Likewise, the babies beg the slightly more intense circle and two stripes of each parent for food.
The critical importance of UV pigment in budgies almost certainly lies in the precise ability of adults and babies to locate each other for the regurgitation and exchange of food in dark nesting hollows.
Baby Gouldian finches also have UV mouth markings, visible mostly when they are gaping for food from their parents.
Now. what links the Budgerigars, the Gouldian finches, the wombats and the Platypuses together? Simple, they all nest in dark burrows or dark hollows in trees. Platypuses and Wombats are also nocturnal. As I mentioned above, although budgies have very poor vision in low natural light, they see very well in low UV light, where we humans are pretty much blind. Thus, in hollows and holes, they have useful amounts of vision if they possess amounts of UV pigment.
In the recent article in New Scientist, the author said, in animals: “Biofluorescence is typically used for communication or camouflage, but that makes no sense in a nocturnal species. Scientists are completely baffled by what this is all about”. The answer to this was in my 2009 article.
Standing alone under our house, with almost no white light, then with just weak black UV lighting, the answer was clear. Animals which have UV light vision, can see in low levels of UV light, if UV fur, feathers or skin are present. We humans can’t see UV light or pigment unless a black UV light is shined upon them to make them fluoresce in our visible white spectrum.
New Scientist magazine said: “The platypus’ pelt glows in UV light, which makes no sense for a nocturnal animal.” Platypuses and Wombats live in long, dark tunnels and are nocturnal, so they almost never see the light of day. They do however see UV light.
I have been selecting for greater UV Glow in budgies for many years now.
Some lichens also reflect UV glow under black UV lights. It is hard to explain why this could be an advantage to this hybrid group. Lichens are a symbiotic relationship between an alga and a fungus.
© Don Burke.