Chandima Fernando
Ecolgist/GIS Specialist
SLWCS

In Wasgamuwa, Sri Lanka, the dominant forest type is “Dry Mixed-Evergreen Forests” which are characterized by having various fruiting trees. Amongst them, Palu (Manilkara hexandra) and Weera (Drypetes sepiaria) are the most dominant fruiting trees. Generally in tropical forests, 50-70% of trees bear fleshy fruits that are consumed by a large variety of animals.

The Palu or Ironwood is a hard wood tree. The trunk is generally blackish grey and vertically furrowed. The leaves are small and dark green. The shape is broadly obovate. Flowers are yellow, with numerous in leaf axils. Weera is also a hard wood tree with the trunk often twisted or fluted. Flowers are axillary clusters of short racemes.

Both species have some medicinal values. Palu has been used to cure oral diseases such as gum diseases and Weera used as an antioxidant especially by some tribal communities in South India to treat scorpion bites and is also used to reduce rheumatic inflammation.

The fruiting season of both trees is between May and July. The shapes of the two fruits are different. The Weera fruit is spherical in shape while the Palu fruit is more elongated. Fruits of both species are in green colour when they are unripe. The cryptic green colour of immature fruits is an evolutionary adaptation by the plants to reduce the chances of getting consumed specially by non-disperser species before they are fully ripe. When Weera fruits are fully ripe they become glossy red-orange whereas Palu fruits become bright yellow. In general, bright colours increase the attention of the frugivores which is an evolutionary adaptation of the trees for effective dispersion. It is very obvious that Palu and Weera trees have an extra advantage over other fruiting trees in the area, by having bright coloured fruits to attract a lot of frugivores belonging to different taxas, such as birds, civets, monkeys and bats in Wasgamuwa.

Unlike Weera that bears fruits annually, Palu does not fruit annually. In some areas, fruits happen every two years. The exact reason for this phenomenon is not yet known.

This year, in Wasgamuwa, almost all the mature Palu trees started to blossom in late April hinting a good Palu fruit season. By mid-July, the Palu trees became very noticeable since every twig in the branches was laden with bunches of yellow coloured fruits.

I have tasted Palu fruit several times previously, but not in Wasgamuwa. So, I waited eagerly to climb a good Palu tree to taste some of the fresh succulent fruit.

In Wasgamuwa there is a place called “Palu Pitiya” meaning the field of Palu trees since it is a large area predominantly dominated by Palu trees. I was lucky enough to go to this area this year. So for the first time this year as luck would have it, we were at Palu Pitiya on June 23rd and as expected, every tree in Palu Pitiya was festooned with yellow fruits. When we got there, we could not help climbing the trees to pick some of these fresh fruits. After satisfying our cravings with hundreds of sweet Palu fruits and spending more than an hour for that, we suddenly realized that we had to re-focus on our main work, setting up our remote cameras. Palu fruits are very sweet and hence a very good energy booster especially during the hot weather. So, we tool some fruits to snack later.

Throughout that day, we stopped at several different Palu trees to taste the fruits. This is because the villgers in Wasgamuwa say, the taste of the fruits vary from place to place. They were right of course, the sweetness of the fruits differs from place to place. All of us unanimously agreed though that the best Palu fruits are from the trees at Palu Pitiya.

During this time, Weera trees were also laden with fruits. However, compared to Palu fruits, Weera fruits are not that sweet, sometimes an “over dose” of Weera fruits, can make your throat very dry.

No surprise that we were not the only ones attracted to these wild fruits! The huge amount of bear scat that we came across with the Palu and the Weera seeds clearly indicated that the sloth bears were actively exploiting such a bountiful harvest.

It is well known that the Sloth Bears love both the Palu and Weera fruits. During the fruiting season in places like in Yala, Willpattuwa, Bundala and Kumana National Parks, you can easily observe bears feeding on Palu and Weera fruits during the day time. However, in Wasgamuwa, even during the Palu and Weera season, sloth bears seem shy to come out during the daytime and seem to be feasting mostly during the night time since we never came across them during our forays into the jungle during the Palu season.

Over ripe Palu fruits get fermented quickly and it is known that the bears get intoxicated after eating those fruits. Mind you, we also felt a little tipsy after consuming over hundreds of those Palu fruits!! In some parts of the country, bears are called “Weera Muththa” in Sinhala because of their fondness towards Weera fruits.

Sloth bears are mainly myrmecophagous, feeding on termites, ants and other insects. However, during the fruiting season, they become more frugivorous, and fruits like Weera and Palu form a major component of their diet. Data from our remote cameras show an increased level of activity patterns of bears closer to Palu and Weera trees.

Apart from Palu and Weera, sloth bears also love to eat the seed pods of the Ehala (Cassia fistula) tree. Ehala seeds are bitter for human taste but it appears that the bears enjoy the bitterness. A camera that we had set up on an Ehala tree provided us with clear evidence of that. A mother bear came to eat fallen Ehala pods with her three cubs for several consecutive days.

The sloth bear is an omnivore that feeds on both insects and fruits, we can use the information on the foraging habits of bears as bio-indicators to the monitor the changes in the forest patches that they inhabit. Hence, we need to conduct scientific research to understand the food habits of the bears and how it changes spatially and temporally. Being a mobile and far-ranging frugivore, sloth bears could play an important role as seed dispersers in forests like Wasgamuwa but again we do not have sufficient information about that and hopefully our Carnivore Project will help us to understand these habits of the illusive sloth bear.

Photo Credits:

Chandima Fernando/SLWCS
S.P.C.I.E.S.E/SLWCS Carnivore Project

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