JRBP Ant Survey

Argentine ants are a worldwide invader. Native to Argentina, they were first recorded in the US around 1890 in New Orleans. They arrived in California approximately 15 years later and have spread throughout much of the state. They are considered a pest in agricultural and natural systems.

Graduate student Katie Human and advisor Stanford Professor Deborah Gordon started the Jasper Ridge Argentine ant survey in 1993 to track the invasion of Argentine ants into Jasper Ridge. Twice a year, volunteers search for ants at survey sites throughout the preserve, so researchers can map the spread of the Argentine ant and native ants. This survey is now the longest continuous fine-scale study, in our knowledge, of an insect invasion in progress.

This long-term study has made important contributions to understanding invasions in space and time and numerous publications have emerged. Early on in the survey, Argentine ants were invading new areas of the preserve rapidly. As they advanced, native ants disappeared. The spread of the Argentine ants increases during years of high rainfall. But since about 2000, when the current drought began, the invasion has stalled. The native winter ant, Prenolepis imparis , competes with the Argentine ant for access to the scale insects whose sugary excretion is food for both the ant species.  As the drought has deepened, the winter ants seem to be moving into areas where the Argentine ant used to prevail, and even displacing them.

Some of the questions we can ask are:

• How will climate change, bringing drought and decreased biodiversity, affect ant distributions?
• How do native ants coexist with Argentine ants? What determines which species gets the food?

The ant survey provides essential information on the micro scale habitat requirements of the Argentine ant, which is  critical to managing Argentine ant populations. Long-term data provides the opportunity to learn more generally how the area occupied by a species can change, and how this shifts the web of interactions among species.

A group of dedicated volunteers, the Gordon Lab,  and Jasper Ridge have established an ongoing survey program to ensure continued monitoring each year. 

• Survey members include researchers and volunteers from the local community.
• The survey takes place on a Saturday morning, twice a year, once in the spring and again in the fall.
• A brief training session to teach basic skills in ant identification and data collection is offered prior to each survey. Then volunteers work in pairs.

For more information, please contact the antsurveyJRBP [at] gmail.com (Ant Survey main email) or Ant Survey Coordinator, Angie Nakano