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The Butaan Project - Foraging behaviour Print E-mail

butaan7.jpgWe use feces to investigate diet and activity areas of butaan. In total we have examined more than 1500 samples, possibly the largest ever collected for a single population of reptiles.  Butaan and their relatives are huge specialised frugivores, much bigger than any other specialised frugivorous animal in  the Philippines. They need a constant supply of fruit but lack the wings that allow other frugivores to forage in different forest fragments. Large and immobile, the butaan depends on a very narrow range of foods.



Butaan on Polillo eat fruit and snails. Sometimes they eat crabs and another animals, but this is rare. Butaan require a mixture of fruit species that are taken either simultaneously or consecutively
The most abundant fruits are only eaten when preferred fruits are not available. Many plant species important in the diet do not show a clear fruiting cycle. Although there are hundreds of fruits in the forest that have the potential to be food, butaan only feed on a very narrow range of mainly large-seeded species. The seeds pass through the lizards without damage and so the lizards act as seed dispersers for the plant. There are few competitors for most of the fruits eaten by butaan. Some of these fruits seem to have evolved to attract large animals, such as elephants, which no longer exist in the Philippines. The butaan has been able to exploit these resources and has evolved a unique ecological niche. At the same time it has provided a very unusual method of seed dispersal for plants that have very limited dispersal strategies, such as Pandanus
700+ species in Africa, Asia and Australasia. 40+ species in Philippines.
Mainly distributed along coasts and waterways.
Exclusive microhabitat of many endemic species of vertebrates, invertebrates, plants and fungi.
Most species are dispersed by water, others by crabs, turtles, rats and by butaan in the Philippines.
We suspect that butaan has a marked effect on the understorey of forest throughout its present range by dispersing Pandanus seeds. This results in high densities and unique distribution patterns of Pandanus on ridges and slopes - clumps of seedlings uphill of any possible parent plant.

This also suggests that areas where the animals were present in the recent past may still show unique patterns of Pandanus distribution.

In recent years we have mapped the distribution of Pandanus and other species in different forest patches and are measuring the seed shadows produced when butaan feed from a tree. The results will shed light on the butaan's role as a seed disperser and how it can alter the dynamics of the forest understorey.





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William Oliver. Champion of biodiversity and its students. So many of us benefited from his advice and expertise. What a character. RIP.


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The Butaan Project
The Butaan Project - Background and History
butaan2.jpgThe butaan was first described to science in 1845 from a juvenile specimen collected by Hugh Cuming. It was labelled only "Philippines". It was named Varanus grayi.  No other specimens came to light for over 120 years. In the 1970s Walter Auffenberg found another specimen with a location in Luzon, established that its correct scientific name was Varanus olivaceus, and undertook a 22 month study of the species based in Bicol. His study revealed that butaan occupy a unique ecological niche and have a lifestyle quite unlike any other monitor lizard. Auffenberg used local hunters with dogs to catch the animals. Of 126 butaan caught during his study, 116 animals were killed.


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