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The Butaan Project - Research Print E-mail
butaan3.jpgThe only obligate fruit-eaters among reptiles are three species of monitor lizard that live in the Philippines. Frugivorous vertebrates tend to be able to fly (almost all are bats and birds) and so these lizards have a unique ecological role as highly specialized and relatively immobile fruit eaters. Before this project started, the only studies of this unique giant and endangered lizard had involved killing the animals. We have developed a set of techniques that allow us to learn about these animals in a completely non-destructive way.

ImageThe only obligate fruit-eaters among reptiles are two species of monitor lizard that live in the Philippines. Frugivorous vertebrates tend to be able to fly (almost all are bats and birds) and so these lizards have a unique ecological role as highly specialized and relatively immobile fruit eaters. Before this project started, the only studies of this unique giant and endangered lizard had involved killing the animals. We have developed a set of techniques that allow us to learn about these animals in a completely non-destructive way.

Fruit eating monitors require foraging strategies that are unlike any other reptile. They require constant supplies of at least two types of fruits from within a very narrow range of types. Some of its food trees are very common but have unpredictable fruiting patterns, others are very rare or have a very short fruiting season. Individuals must develop spatial maps in order to remember the location of important food resources within a very complex forest environment.Image

Using thread (and camera traps) we have been able to demonstrate that lizards remember the position of food trees at least two or three hillsides away, that young animals will revisit important resources more often than they feed there, that that even old animals (perhaps 30 years old) have an imperfect knowledge of key resources in their activity areas and that social facilitation plays an important role in location of some resources. We hope to develop this study to investigate how lizards develop spatial maps in intact and severely fragmented habitats. The butaan is an ideal study animal for this subject because it is relatively immobile (i.e. a frugivore that cannot fly), its food resources are relatively easy to map and its fruit requirements can be predicted to a large extent.

We study the diet of the butaan by finding its droppings on the forest floor, and use them to determine seasonal and spatial changes in diet and variation between years. In total we have found almost 1000 fecal samples on Polillo Island, one of the largest samples for any single population of lizards, and are able to identify the critical food resources that the animals depend upon. We study the fate of seeds dispersed by the lizards to understand the effects of the butaan on forest structure and its importance as a seed disperser.Image
    
To learn about animals movements scientists usually track individuals with transmitters or GPS devices. Both methods usually provide spot data showing the animals position at a particular point in time rather than information on actual movement. Furthermore both methods are expensive, prone to equipment failure and present considerable problems when it comes to getting the devices off the animals. Some animals can also be tracked by observation, but not many, and the butaan is definitely not one of them! On the occasions we are able to rescue butaan from traps or hunters we release them with ingenious spool and line devices that let us track their exact movements over several miles. Image

Because butaan are shy and very easily disturbed there is no easy way to count animals and monitor changes in population sizes. We rely on camera traps and hides to record visits to critical trees and monitor individual animals over time. In total we have monitored trees for almost half a million hours and recorded visits to some trees over three years. Certain trees are critical to butaan survival and we are able to identify these resources and take steps to protect them.

 
 

 

About Mampam
Bye Bye Butaan

 butaan1.jpg

Butaan start to visit fruiting trees before they are large enough to swallow the fruits. They make repeat journeys to trees, perhaps to reinforce memory of the position of the tree. If the youngster survives it may continue to use this tree for many decades. Fruiting trees like this are a vital resource for entire populations of butaan. Learn more >


 
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The Butaan Project
Monitoring Individuals 3
The best way to monitor individual butaan would be to extract DNA from fresh feces found on the forest floor. We can find the feces but we cannot afford the analysis!
 

 

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