Ant Invasion: How Pets Become Pests

When I was a teenager, I volunteered at the rainforest exhibit in an aquarium. A few times a week we got a call from someone who wanted to donate a pet that he could no longer care for. Mostly turtles and frogs. Occasionally a parrot. Once upon a time, a retired dancer wanted to find a new home for two boa constrictors who were part of her act.

But the aquarium couldn’t handle all the animals on offer and I often wondered what happened to all those unwanted pets. Many have probably found new homes, but unfortunately some have probably been released into local parks or ponds.

This four-foot, 43-pound Burmese female python was discovered a few feet from an upscale residential neighborhood in Naples, Florida. Most experts believe that released pet pythons established a breeding population in the mid-1990s.

A recent study by researchers at the University of Lausanne warns that the pet trade is contributing to the spread of invasive species around the world. The study, published in the Proceedings of the National Academy of Sciences (PNAS)found that traded pets are often invasive species, meaning they establish natural populations in new places.

These pets are not just larger animals that are sometimes released into the wild when they outgrow their cages, such as the Burmese pythons that have invaded the Florida Everglades, but even a relatively new and apartment-friendly pet: ants.

Ants are popular pets

I study ants, which makes me a myrmecologist, and I sometimes keep live ant colonies for research purposes in my lab. At one point, I had nearly 100 live ant colonies for a study comparing invasive and native ants as seed dispersers.

I collect wild ant queens and workers from a biological station near me and house them in test tubes, which I wrap in aluminum foil and partially fill with wet cotton. This keeps the test tubes moist and dark, and usually the queen and her workers get in right away.

A test tube with ants and closed with cotton balls.
A queen ant and others in an ant farm test tube.

Because ants are easy to care for and downright fascinating to watch, they are quickly growing in popularity as pets. According to the PNAS study, at least 65 websites now sell and ship ants around the world.

As a myrmecologist, I love that others find joy in ants. Ants have complex social lives, play an important role in ecosystems and are capable of truly remarkable things.

Some ants join their bodies into floating rafts or bridges to cross water or other obstacles. Others are smart enough to think of and remember the most direct route home.

One of the ant species I’m studying creates huge gardens of its host plants in the Amazon rainforest by poisoning all other plants with formic acid. There are more than 15,000 species of ants on Earth and they live on every continent except Antarctica. There have even been ants in space.

I love ants, so I can’t blame people for wanting ants as pets.

Ants have complex social behaviors and can work together to solve problems, including building a bridge to carry food across an open space.

House ants are often invasive species

But some ant species are also very serious pests.

Five ant species — Argentine ants, red imported fire ants, yellow mad ants, little fire ants and big-headed ants — are among the top 100 worst invasive species in the world because they can have devastating effects on local ecosystems. Invasive ants often outnumber native insects, harm birds that nest in the ground and in burrows, and help spread other pest species.

The PNAS research found that 520 species of ant are traded as pets, of which 57 species (or 11 percent) are known to be invasive, compared to just 1.7 percent of ants overall. Interestingly, the pet ant trade is new enough that those 57 invasive ant species probably haven’t been introduced to new parts of the world by pet owners.

Instead, the new research highlights that the same traits that make animals good pets often make animals good invaders. For example, invasive ant species usually have colonies with more than one queen, and multi-queen ant species are also more commercially successful pets.

Ants crawling over a pale gecko
Yellow mad ants attacking a gecko in India.

Because some of the ants I study in my lab are invasive species, my lab members and I take extra care to make sure our ants don’t escape. We place the ants’ test tube nests in plastic Tupperware containers that we coat with a special substance called Fluon, a milky-white resin that makes the walls of the containers so slippery that ants can’t climb into them. Then we put the containers on shelves with legs that stand in small dishes with mineral oil. When a wayward ant runs towards it, she gets trapped in the oil before she can get to the door.

But people who keep ants or other invasive animals as pets may not be so careful.

Fortunately, there is an easy solution: do some homework when looking for a new pet and consider choosing a species that is native to your area.

Ant lovers can even collect a colony locally. Ants are so diverse and abundant that there is a good chance that you will be able to find an interesting and suitable native ant species near you no matter where you are in the world. Remember that you have to find a queen to keep the colony going. Then sit back and enjoy your love for ants.

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