What a Difference Rain Makes

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Clouds and fog in the normally dry mountains near Cerro Venado.

Russ is studying wild Andean (or spectacled) bears in the Lambayeque region of Peru and sharing his adventures with us. Read his previous post, Finally, a Little Bit of Rain.

Wow, what a difference a little rain makes in the dry forest! When I woke up this morning, I walked away from the base camp to look at the clouds and fog rolling through the valleys. It was just before dawn, and at first I thought it was still raining. Then I realized that what I thought were raindrops falling on me were actually flying ants!

A swarm of flying ants congregating and competing to mate after two days of rain.

After some rain, in this dry forest and in many dry habitats around the world, reproductive flying ants leave their colonies and aggregate in an attempt to mate and reproduce. Most ants in any colony do not fly, and these swarms do not last long. They tend to occur near high points, at least in the dry forest, and our base camp is located along a ridgeline. So, there are several large clouds of flying ants rising up over our camp, and near our camp. Each of these swirling clouds of insects is at least 2 meters (6.6 feet) wide, and up to 10 meters (33 feet) tall. They’re amazing!

As the light of the sun seeps through the dark clouds, I can see that the color of the landscape is changing. Instead of being brown, as it was only a day or two ago, it’s becoming bright green! There are thousands of tiny plants at my feet, each shorter than the width of my little finger. I have no idea what kind of plants these are, but it is impossible to walk anywhere without stepping on them. I knew that arid habitats often have an abundant number of seeds waiting in the soil for just a little moisture to trigger germination and growth, but it is one thing to “know” that something happens and another thing to see it right in front of your eyes. I can almost hear the plants growing…

Russ Van Horn is a senior researcher with the San Diego Zoo’s Institute for Conservation Research. We’ll be posting more about his trip every few days!