(Roughly) Daily

In addition to being home to men with questionable decision-making skills, Florida also seems to have some issues with bizarre animal behavior, whether it’s freezing iguanas dropping from trees or alligators battling pythons in the Everglades. When it comes to those animals, however, Floridians can truly put the blame on non-natives. Neither pythons nor green iguanas made the Sunshine State their home until we brought them there as pets.

In fact, there are lots of problematic invasive species that have spread through the pet trade, from predatory fish that can drag themselves between bodies of water to a crayfish that clones itself to reproduce. Those high-profile cases lead to some obvious questions, like whether pets really are more likely to be invasive and, if so, why?

Two Swiss researchers, Jérôme Gippeta and Cleo Bertelsmeier have now attempted to answer these questions. And their conclusion is that yes, our pets are more likely to be problems.

To answer the question of whether pets really are problematic, the researchers generated some basic statistics for different groups of animals (mammals, birds, reptiles, amphibians, and fish). These included estimates of the total number of species, as well as the number of those that are classified as invasive and the number that are part of the pet trade.

If pets were no more or less likely to be invasive, you’d expect to see the invasive ones occupy similar fractions of both the pet trade and the total number of species in that group. But that’s not what we see in any of the groups. Invasive mammal species were present at five times the rate in the pet trade as they are in the wild around the globe. There was a similar result in birds; for amphibians, invasive species were eight times more common in the pet trade and about 10 times more common in fish.

Overall, invasive species were 7.4 times more likely to be kept as pets than you’d expect based on their frequency among vertebrate populations.

But cause and effect can be difficult to disentangle. Do we choose species that are more likely to be invasive as pets? Or have pets ended up with more opportunities to invade new environments because we transport them around the world?…

Spoiler alert: it’s the former… A new study finds the factors making them easier to keep also help them spread: “Unfortunately, we like pets that are likely to be invasive species.”

* Mickey Mouse

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As we ponder proliferation, we might recall that it was on this date in 1964 that a different kind of “invader,” the Beatles, set a record: they became the first artists to hold all top 5 spots on the Billboard Hot 100 on the same week, on April 4, 1964. 
#1. Can’t Buy Me Love
#2. Twist and Shout
#3. She Loves You
#4. I Want to Hold Your Hand
#5. Please Please Me. 
More Beatles on the Charts that week: #31 – I Saw Her Standing There, #41 – From Me To You, #46 – Do You Want To Know a Secret, #58 – All My Loving, #65 – You Can’t Do That, #68 – Roll Over Beethoven, #79 – Thank You Girl

At the time, the best-selling piece of Beatles merchandise was the “I Love Ringo” button.

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