Thursday, July 29, 2010 at 4:51PM
When you want to learn about the biology of a charismatic species, any species really, sometimes you end up learning about the grosser side of life too. Thats kind of how I came to take this picture last week in Mexico, where I and several others from the team at Georgia Aquarium have been doing research on whale sharks lately (see several other blog posts heareabouts). It was taken during an aerial survey we did from an altitude of 1,500 ft in a Cessna 206 and shows a whale shark that has just defecated. Now, whale sharks tend to do everything on a giant scale, so perhaps we shouldn't be too surprised, but I estimate the animal to be between 8 and 11m (25-35ft) in length and so, based on that estimate, thats a cloud of poo behind him thats over 30ft in diameter! Its unusual to see wild sharks in the act of pooping, but this group of animals was so numerous and feeding so heavily, that you could actually see several clouds like this at any given time. Whats feeding heavily got to do with it? Well, unlike mammals, which tend to have a relatively fixed gut passage time for food, a lot of cold-blooded critters can, well, sort of push it out the back end, simply by pushing more in the front end.
Far from being a trivial observation of one of life's less savoury moments, it could actually become a really important research opportunity if we can manage to catch some of that magical egesta in a container of some sort, for analysis back at the lab. Scientists can do all sorts of stuff with poo, like looking for parasite eggs or other pathogens, sequencing the DNA of both the shark and its prey species, or comparing nutrient values of food (from plankton tows) and comparing them to values from faeces to work out how much nutrition they are gaining from their food. Its a great way to learn a lot in a short time and do it in a totally non-invasive way.
Mostly though, its a cool photo to gross people out at parties...