Sundaland, a wider landmass linked to Asia has once had islands like Sumatra, Borneo, and Java, but unique species to each island as for example the two species of orangutan, were studied and suggestions as to what kept them apart were created. The study included looking at ancient poo samples.
Sundaland was wider when the sea had its lowest level, and it was larger than today’s Europe. This was approximately 20,000 years ago, at the spike of the last ice age; this meaning that Sundaland was unveiled above sea levels for approximately 90% of the time during the last few million years, and it seems like, currently, it does about 10% of that time.
Bird and bat disposals can explain the Southeast Asian ancient environment
When the sea level was at its lowest, study sites findings conclude that savannas or rainforests existed during that time, as well as the Molengraf rivers, originally recognized from prior bathymetric surveys in 1921.
To find out what the landscapes looked like back then, thick accumulations of bat and bird poo had to be studied from caves within the region. Every night, the bats and the insect-feeding birds would leave their shelter to feed on insects from the regions around the caves.
After returning to sleep, the bats and birds would defecate on the cave floor, acting like mini-scientists, sampling the insects from around the cave: the piles of excrement were mostly composed of insect skeletons, thousands of years old. Their chemical fingerprints can show what sort of plants they were eating.
These accumulations can conclude on what type of vegetation the environment had, and how it changed with time. However, as there aren’t many sources of data, there is no knowing how the Sundaland landscapes were like in the past. Some would say that tropical forests covered the region, just like we see on today’s islands, but there’s also the idea that savannas existed through Sundaland from north to south, flanked on east and west by tropical rainforests, serving as a refuge for animals and plants during ice ages.
Weird species pattern
The Indonesian area is a biodiversity dilemma because lots of species are found only on certain islands and nowhere else, for example, two species of orangutan were found one in Sumatra and the other in Borneo. Also, two species of Sunda clouded leopard, one species in Borneo and the other in Sumatra. This fact is curious and brings forward lots of questions such as ‘how did the species evolve in a separate manner if, mainly, they should have been able to move from Borneo to Sumatra and vice-versa through rainforests, considering that the islands were a whole land’.
The answer seems to have implications for the preservation of many breeds in the area. Christopher Wurster presented in their latest study the conclusions from a pile of ancient excrement dating back to about 40,000 years, found inside the Saleh Cave, located on the southeastern part of Borneo, and at the southern equatorial end of a savanna passage, of one ever existed.
The study concluded that tropical grasses were a main part of the habitat during the ice age, until recently, speaking from a geological point of view. The results also make possible the idea that savanna existed int he north of the equator and tropical forests did retreat and it did not coat Sundaland during the ice age.
The savanna passage acted as a bridge for species adapted to the non-forest landscapes from the north and south parts of the equator, and a fence to the species who wanted to move across Sundaland. This then explains clearly the weird patterns of animal, insect and bird disposals all over the area.