Why are boobies’ feet blue?
One of the most charismatic and famous inhabitants of the Galapagos Islands, the blue-footed booby, is an almost cartoon-like character. Its most obvious feature is its bright blue feet, which really make them stand out as one of the main Galapagos Islands tourist attractions.
In answer to the question ‘why do they have blue feet?’, like all great biology questions, the response depends on the way you look at it. From a simple causal point of view, they have blue feet because of the carotenoid pigments, which they obtain through their diet. The concentration of the pigments depends on the exact dietary makeup, with higher concentrations of certain foodstuffs leading to bluer feet.
Carotenoids also have anti-oxidant properties and stimulate the immune system but since they are absorbed into the feet, in this case, they can’t be accessed by the body in a conventional sense, and therefore not used for immunity or detoxification.
So why don’t the boobies use these beneficial pigments for other means? Charles Darwin’s theory of evolution, that is so inextricably linked to the Galapagos Islands, would seem to suggest that the blue footedness has some other beneficial cause. Otherwise, the blue-footed gene would have died out long ago. So what could this be?
Another reason the blue-footed booby is such a popular Galapagos Islands tourist attraction is because of their unique mating ritual, which involves a hot-stepping dance. So, we can assume that the blueness of their feet has something to do with attractiveness to members of the opposite sex. But what could it be about the blueness of the feet that females find so appealing?
Research has shown that the blueness of the feet is a very reliable indicator of the health and strength of the bird. This is because the bird has more spare antioxidants to store in the feet. So, a mate with bluer feet will produce stronger offspring and offer greater protection. Blue feet are the yardstick by which potential mates measure the trade off between immune function and display.
Science backs this up too, with those chicks raised by parents with bluer feet growing up faster and stronger than those with dull feet. So, it seems like one of the Galapagos Islands tourist attractions has a very Darwinian reason for being – how very apt.
Spotting blue footed boobies on your Galapagos tours, on liveaboards such as the Eden yacht, is a highlight of any tour.