Studying Ants in Crystal Cove’s Backcountry

Take a sneak peek at ecological research happening in Crystal Cove State Park!

In December 2019, we began working with Dr. Wallace Meyer, an insect ecologist from Pomona College, and ten high school interns from Dana Hills High school to determine how the use of mulch in restoration affects the distribution of ants.

Mulch — which usually made of organic material that is spread around the base of planted seedlings — is used in restoration because it helps retain water, blocks non-native weeds from germinating, and adds nutrients to the soil as it decomposes. But Dr. Meyer has found that the use of mulch leads to higher populations of non-native Argentine ants in the inland areas where he’s previously conducted research.

Argentine ants are usually found in urban and agricultural areas because they need more water to survive than our semi-arid climate generally allows for. When they make their way into our coastal sage scrub habitat, they form large colonies that can force out native ants, such as the harvester ant. Harvester ants are important to our ecosystem because they are the primary food source for another Crystal Cove resident, the horned lizard, which is listed as a “Species of Special Concern.” Without harvester ants, the horned lizard doesn’t have enough food to survive.

To determine whether mulch impacts the presence of Argentine ants in coastal areas like Crystal Cove State Park, our interns worked with Dr. Meyer to set up an experiment at our Project Crystal research site in Moro Canyon. The high school interns have been working with us over the past year to collect and analyze data on ant populations, as part of an internship program supported by the Foundation for Sustainability and Innovation.

Now, you’re invited to go behind the scenes with Erick Valdez, one of Crystal Cove Conservancy’s Education Coordinators, as he shows you the process that we go through to collect and analyze our samples!

First, we set up pitfall traps!

Dr. Meyer first set up tube housings for our pitfall traps in our mulch research site last fall. Since then — aside from a brief interlude due to COVID — we’ve been working with the high school interns to put out sampling containers once a quarter in the three treatments being studied: woody much, straw-like mulch, and no mulch. 

In the video above, Erick will show you how we put out traps at the start of a collection interval!

Then, we collect the traps!

Once the traps have been out for two weeks, we collect the samples and see what we’ve found. Erick will show you how the pitfall trap samples are collected in the video above, and show you a sneak peek of some of the specimens that we observed in our most recent samples!

After that, it’s time to sort the ants!

In the final video above, Erick will show you the process we use to analyze and sort the samples!  This lets us see if there was any increased presence of Argentine ants in the mulched plots compared to the non-mulched plots. 

We’re not done with this research yet!  Dr. Meyer is hoping to continue collecting and analyzing samples for another year, and despite restrictions due to COVID-19, our high school students are still hard at work sorting pitfall trap samples from home. But every sample we take gives us another data point to help us understand how mulch affects the distribution of ants in coastal areas.

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