Fighting Invasion With Invasion

When I was but a child growing up in Puerto Rico, visits to El Yunque rainforest were more or less a regular occasion for me and the family. In between nature hikes and dips into freezing cold rivers, as per the norm, I would always notice the same usual signs scattered along the forest paths… “No Littering”, General Safety Info, blocky geometric maps of the forest, etc. But one in particular would always catch my attention: Beware of Mongoose.

Now I’d never heard of or seen any mongoose at that point in my life, but signs advertising the dangers of ravenous mongoose were *everywhere*. I remember asking my parents about them and getting a very parent-like answer on the matter, and that was pretty much that on the subject, but it was continually perplexing to me that there were so many signs warning people of the dreaded small Indian mongoose when I’d never actually seen one. What I didn’t know at the time was that mongoose were indeed all over the place because they were a particularly aggressive invasive species, and had been for more than a hundred years.

The small Indian Mongoose was imported to Puerto Rico by the Spanish in 1877 from the Malay Peninsula in an attempt to control the plague of Black Rats infesting the island’s sugar cane plantations. These Black Rats, coincidentally, were also an invasive species brought over accidentally on Spanish ships during the colonization of the island. I.e. introduction of mongoose into the island’s ecosystem was a failed attempt by the Spanish at rectifying an already serious invasive species problem that they had caused and the irony here is just palpable.

Thanks to the lack of foresight in this very, very ill-conceived plan, the mongoose did indeed prey on the out of control rat population… but their diets consisted of more than just small mammals. They also fed on frogs, snakes, insects, birds, and other small reptiles, and these voracious eaters have to date caused the extinction of at least 12 endemic Puerto Rican reptile and amphibian species. The poultry industry on the island also suffers consistent setbacks, with mongoose causing the island about $50 million dollars in damages a year. Puerto Rico lacks any sort of predators to control the mongoose population, thereby offering them a safe haven in which to breed and consume uncontested. And female mongoose get busy fast, producing up to 36 individuals in a typical four year life span, and being ready to breed at just ten weeks. Adding to this is the fact that a very large number of mongoose are infected with rabies and leptospirosis, so its just a bad time all around.

Today, I don’t visit the rainforest nearly as much as I used to, but I have gone back a number of times since and I still have yet to ever catch sight of the slippery things. Ignoring my own burning childhood curiosity, this should be a good sign, since not spotting any would seem to indicate that they are less populous now than they used to be. But the IUCN has the small Indian mongoose listed as one of the top 100 world’s worst invaders for a reason. Those warning signs are still up and still everywhere, so it might very well take another hundred years for nature to rectify itself and for the forest to finally be rabid mongoose free.



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