How do Guatemalan beaded lizards use scent to locate food?

Scientists at Zoo Atlanta recently published a study conducted in collaboration with students and faculty from Georgia State University and Georgia Tech. The study investigated how Guatemalan beaded lizards (Heloderma charlesbogerti) use two different mechanisms of scent detection to find their prey.  

Most vertebrate species (including humans) sense chemical signals in their environment through olfaction of airborne scent molecules. But a great many animals use a closely associated, but nonetheless distinct, mechanism called vomerolfaction. Humans lack the ability for vomerolfaction, so it is difficult for us to interpret how such animals sense their world. 

In many lizards, including beaded lizards, and all snakes, the tongue is used to gather usually scent molecules and then deliver them to the sensory organ (sometimes called the Jacobsen’s Organ) on the roof of the mouth. The tongue itself does not accomplish smell; it simply gathers the scent particles and moves them to the sensory organ. 

We placed lizards in an eight-arm maze that was partially blocked to form a simple T-maze where one arm was baited and one arm was left empty. This was designed to investigate if lizards could locate food from a distance via olfaction of airborne scents. The bait was their usual diet of frozen-thawed baby mice. It turns out that the lizards were unable to smell the food from a distance, strongly suggesting that they were not getting cues via olfaction.  

However, when the food was dragged to create a scent trail on the ground, the lizards were successful at following the trail to find food. This research helps us understand how lizards use their senses in the wild: likely by following scent trails to find prey like bird eggs and small animals, hidden in trees or underground. 

But don’t worry, none of the lizards were ever denied their food! All the lizards got to eat their mouse treats at the end of each trial. 

The Guatemalan beaded lizard is a critically endangered species that is native to only a portion of a single valley in Guatemala. Zoo Atlanta maintains the largest conservation-breeding group of this species in the world and has been collaborating with Guatemalan conservation organizations for over 20 years to develop conservation programs that include breeding programs, habitat protection programs, and local outreach-education programs in its native valley.  The species is threatened by habitat loss, poaching for the pet trade, and, historically, fear-based persecution by local persons. Fortunately, our collaborative programs are working well, and the status of the species is slowly improving. It is estimated that between 500–600 lizards exist in the wild. Zoo Atlanta has hatched more than 40 of these amazing lizards.  

• Haseltine, E. L., M. D. Englund, J. L. Weed, M. J. Beran, H. Tao, S. Paschal, and J. R. Mendelson III. 2024. Guatemalan beaded lizards (Helodermatidae: Heloderma charlesbogerti) navigate and follow a scent trail in maze tasks. Journal of Comparative Psychology. https://dx.doi.org/10.1037/com0000394