The Tortoises of Aldabra

Aldabra is an isolated atoll in the Indian Ocean, with a human population of 15 and a giant tortoise population of 100,000, the largest giant tortoise popultion in the world. The largest wild-living tortoise is currently over 360kg (almost 800lbs), and still growing. The tortoises on Aldabra will often wallow in freshwater pools when such water is available, even dozing with their heads underwater. Unfortunately, they also see nothing wrong with defecating in these pools, which eventually get somewhat... whiffy...

Fast-forward 11 months on from the previous photo, and the cool pools in which the tortoises could rest have become a treacherous quagmire. It's not rained now for five months and the water that has not evaporated has become a thick mass of mud, algae, bird faeces and tortoise dung. It is undrinkable and the rains - a month late this year - will not arrive for another two months.
This is the start of the hardest time of year for Aldabra's giant tortoises, and many die of dehydration. The increasing length of the dry season appears to be a trend, possibly associated with anthropogenic (human-caused) climate change. As Aldabra's animals live on such a knife-edge, this trend could spell ecological disaster.

Almost two months later, and it's now been 7 months without rain. Even the muddy quagmires that provided, if not drinking water, at least some respite from the burning sun, are gone.
The only reachable plants have no nutritional value and the tortoises are starving. Desperate, these lumbering herbivores resort to cannibalism; they begin to eat those fellow tortoises that do succumb to the drought to recover any nutrition they can. They are nearing breaking point, and if the northwest monsoon season doesn't start soon they will start to die in droves.

Rain! Two days after my previous photo, and the northwest monsoon has arrived. Two days after that, the grass is growing again. Within weeks, the tortoises will be breeding and producing the next generation, which will still be walking the atoll many years after we're all dead and gone. Now is a frantic time; a time for mating, fighting, and replacing lost water and fat reserves.

After the initial flurry of post-rain activity, life is good. There's plenty of food, plenty of water, and the pools have again refilled. The tortoises will spend hours resting during the heat of the day, and have been seen apparently napping with their heads underwater for up to 15 minutes.

In a few short months, water levels will begin to dwindle, and the cycle will start again.

Until then, they still continue to crap in their pools.

I spent just over a year as one of the fifteen, as a researcher on Aldabra Atoll World Heritage Site. If you have any questions, just send me a message or tag me in the comments.

Tiny tortoise tax! Sorry cat lovers (i.e. All Of Imgur), we don't have cats here; they eat baby turtles and tortoises...