Why can't brown Treesnakes be poisoned or trapped in the same manner as rats?

There are a number of difficulties associated with attempting to poison brown Treesnakes partially because of the way they forage in the wild.  Snakes are very selective about what they eat.  They will often refuse to eat real bird eggs if they have been refrigerated, have been washed, or are below a typical body temperature of a bird.  All of this suggests that the snakes use more than the appearance of potential prey when considering their next meal.  Also, evolution has helped snakes develop natural defenses against consuming potentially harmful substances: they will often regurgitate or pass indigestible materials if they are accidentally consumed.

Another difficulty in poisoning brown Treesnakes involves the type of substance that needs to be used to attract snakes.  Snakes are quite particular about their food and are usually not fooled by fake baits, so poisoned prey items such as eggs, meat, or other attractants would be needed.  The problem with this idea is that many other organisms include the same food items in their diet, and in targeting snakes in this manner, birds, mammals, other non-target reptiles, and even household pets could be put at risk.  However, research is ongoing in this area as behaviorists, physiologists, and chemists work to develop substances that will attract snakes without putting other animals at risk or perhaps to deliver a kind of snake birth control to keep those already in place on Guam from further breeding.

Trapping is ongoing on Guam in areas that require low snake densities such as cargo loading docks for air and ship traffic and endangered wildlife enclosures.  This tactic works well for limited areas, but requires constant monitoring and on a greater scale is next to impossible.  To effectively trap the snakes, traps must be set approximately 15 m apart and require daily monitoring.  Since an artificial snake attractant has not yet been identified, live lures must be used, requiring stores of food and water and protection from the elements such as direct sunlight and rain, which cause further limitations.  Certain areas, such as limestone cliffs, are largely inaccessible for humans maintaining traps but are prime snake habitat.  Restricted military areas and private property cause additional difficulties.  Finally, besides the cost involved in creating, setting, and maintaining traps, vandalism frequently disrupts efforts in populated areas.