Monkeys and Marsupials – Indonesia

An interesting phenomena occurs in Indonesia in regards to the animal life found in the country. Have you ever heard of the Wallace Line? What about the Weber Line or the Lydekker Line?

Most people would answer no to these questions. What if I was to mention that all of the above names belong to prominent biologists? The Wallace Line was named for one of the preeminent biologists of the 19th century, Alfred Russel Wallace, who wrote his life’s work “The Malay Archipelago” based on studies of Indonesian fauna. Along with Charles Darwin, Wallace is one of the founding fathers of the Theory of Evolution.

Monkeys and Marsupials

So what do these lines actually mean and what do they have to do with Indonesia? Simple, these are lines of demarcation that separate Asian animals from Australasian animals. Let’s put it this way, one of the more popular questions we receive when visiting Raja Ampat is: “What kinds of monkeys will we see in these forests?” The islands of the Papua area are covered in primordial forest and jungle which looks like the perfect habitat for monkeys. With the sound of raucous bird calls heard while cruising on a kayak or paddle board, guests often mistake their screeches for the call of monkeys. Needless to say, guests are surprised to hear that there are no monkeys to be found for hundreds of kilometers. “But why?” they ask, suprised that they would not be living in such perfect habitat.

Fauna and Flora and Boundary Lines

This is where it all comes back to the Wallace, Weber, and Lydekker Lines. You see, from a host of observations over many years Wallace was the first to theorize that there was a distinct difference of speciation between the eastern and western sides of a line that runs from the east coast of Borneo south through the channel between Bali and Lombok. West of the line there is an incredible array of Asian animals, but as soon as you cross the “Wallace Line” the numbers dwindle. The line itself marks the boundary of where the ocean itself was too deep for most animals to cross during an ice age where the sea level was much lower.

You see, a lot of the population of humanity and animals moved west from Asia toward Papua and Australia during ice age times when a “land bridge” made movement easier. However, deep channels that did not have “land bridges” stopped many animals from moving any further east.

Moving the Line East

Although the theory behind Wallace’s Line are sound, he was not quite correct on the boundaries. Many species of monkey, deer, pigs, and others are also found further east. With further study, Max Carl Wilhelm Weber established a line west of Halmahera and east of the Tanimbar islands which proved a more precise boundary between the mammals of Asia and the marsupials of Australasia. Later work by Richard Lydekker moved the boundary further east and included Halmahera to the Asian boundary.

Australia is home to very few natural true mammals. Famous animals of Australia include wombats and kangaroo which are in fact marsupials. The same is true for the island of Papua, the native animals are mostly marsupials. In fact, the only native mammals for both Australia and Papua are bats. Even the rats, mice, and dogs (dingos) have been imported with man.

No Monkeys in Raja Ampat

And of course this is why you won’t find monkeys in Raja Ampat! In other areas of Indonesia that we visit, including Komodo, we find the infamous crab eating macaques. In the island of Sulawesi, we also find several other species of macaque. Java, Sumatra, and Borneo are home to a wide variety of monkeys but very few marsupials.

If you are interested in observing monkeys while in Indonesia, or visiting the incredible Orangutans, we are happy to assist. We work with sustainable operators who conduct nature tours throughout Indonesia. These are great additions when planning a private yacht cruise with Samata. Extending your trip either a week before or after the cruise is a wonderful way to maximize your visit to Indonesia.