I saw a recent report saying scientists have estimated the number of Emperor penguins in Antarctica by using satellite images to identify rookeries. These can be seen as brown smudges on the ice – each the result of thousands upon thousands of penguins poo-ing. Higher resolution images are then used to assess numbers of individual birds at these sites.
It’s probably impractical – as well as far too costly – to use satellite imagery to count elephants here in our environment in Cambodia. But in passing through the forests, it’s not uncommon to come across the football-sized dung balls that show us where the elephants have been.
So how do you count elephants? Elephants are large animals but in these forests they’re often surprisingly difficult to see, and they are spread over an area of 6000km2. It’s like looking for needles, albeit very big needles, in a quite enormous haystack. Elephants also move around, so how is it possible to know we’re not counting the same animals more than once? It does help that they often move in groups – our team members have seen herds of up to 15 individuals – but each group is still only a small proportion of the total number.
Like the penguins, the answer lies with the elephant dung.
Over many years the rangers patrolling these forests have noted each time they see elephants, and so over time we have built up a map of where they live.
Specifically targeting these key areas, the research team went out over the late dry season (when elephants tend to stay in a restricted area so they can access water) and in a systematic way collected 270 samples of elephant faeces. These were sent to a specialist lab in India where, by looking at the DNA, it was possible to determine that these came from 98 different elephants.
The data was then treated with some clever statistical package (to take account of the fact that we probably didn’t find all the dung, that we didn’t collect from every part of the forest and so on) and the results showed that, in total, there are about 136 elephants in Phnom Prich and a minimum of 21 in Mondulkiri Protected Forest.
Rather excitingly, the DNA results also showed clearly that at least one elephant had migrated between the two forests – and so all the more reason to make sure the forest corridors between these two remain intact.
Similar work has been done in these forests for an animal that is probably even harder to find – the leopard.
In this case we combined information from camera traps – leopard spots make it easy to identify individuals – with information on DNA from leopard droppings. This was no easy task – their droppings are small, and break down fast in the tropics.
This time we turned to sniffer dogs, like the ones that are used to find drugs at airports, and which can be trained to specifically sniff out leopard poo. Two dogs (called Scooby and Sadie) walked 585km with their handlers and found 151 droppings which were good enough for analysis.
These turned out to come from eight different leopards (plus quite a few from other species, so the system isn’t entirely foolproof!). Importantly, all this information allows us to estimate that there are 3-4 leopards for every 100km2 of forest.
The elephant and leopard surveys are good examples of the realities of working in these forests. So much of what we know does not come from sitting and watching the animals we want to know more about, but rather from the meticulous collection of indirect evidence.
But why does it even matter that we know how many animals live here? In the elephant case, we had the pleasant surprise that we could show that these forests support the largest population of elephants in Cambodia – further strengthening our argument for their protection.
Perhaps more importantly, it also gives a measure of how healthy the environment is – and therefore how effective the protection is being. By periodically repeating these studies we can determine whether populations are declining, have stabilised or, as we would hope, are increasing.
Working in an environment where it is difficult to see many of the animals that we care about, research is often the only way of letting us know whether we are being successful or not – even if it means spending a lot of time, as one of our wisecracking colleagues said, going through the motions…