Here in the South we get our share of troubling wildlife: fire ants, black widows, brown recluses, the occasional scorpion, and all four types of North American poisonous snakes. Then there are the gators, black bears, and other predators in the hinterlands. Of course, the assortment out west is sobering, too: grizzlies and brown bears are nothing to sneeze at.
Still, in the suburbs where I live the species that cause the most headaches are mundane. Cockroaches are a nuisance, but rats take the prize. The rodents show up inside gardens, crawl spaces, walls, ceilings, attics, and woe to you if rats get into your ductwork. After a while, everything starts to look like a rat. There’s Rattus rattus (ground rats), squirrels (tree rats), bats (air rats), children (rug rats), athletes (gym rats), politicians – no, no, let’s keep this edifying, though I note that Germans refer to their town hall as the Rat•haus.
Recently I learned that plantings may contribute more than food to our rat population. A study found that drinking a water extract from the fruit of either fig (Ficus carica), cinnamon, or fumitory (also known as earth smoke; poppy family) can double or triple the likelihood that adult rats will try to make little ones. The fig nearly matched the best-known synthetic drug for that purpose (sildenafil/Viagra®), used by humans. I suspect the rat study was less interested in animating rodents than in gauging the potential effects on humans. Research is sneaky that way.
So, this gives me a new criterion for which plant species get inflicted upon my yard. You see, three Ficus carica trees have materialized on my lawn since the study was first published, because the effect wasn’t on our personal radar until now. Hopefully one of the neighborhood red-tailed hawks will spot any fig-loving rats yet leave foolhardy small terriers alone.
Now if you’re like me – and I won’t pretend that’s a good thing – you’re wondering which molecules inspire a rat. After a high-level analysis, the authors vaguely credited the flavonoids in each of the three plant species. You remember flavonoids. They’re antioxidants, made famous in chocolate. Oddly, no one knows the molecular source of chocolate’s charm for Valentine’s Day, though its efficacy is never in doubt. In light of flavonoids’ oft-studied drug effects and thousands of structural variants, they were a fair guess as to rats.
So how can I leverage these insights? I’ll keep cinnamon at bay. That’s easy; it’s mainly East Asian. And don’t drop cinnamon sticks on my property; the spice makes elderly rats frisky. The fumitory is also distant – mainly in North Africa, West Asia, and continental Europe. It turns out sycamore fig trees are okay, but my family is already committed to F. carica.
Which other plants should I ban from my yard? Many species have never been tested for their effects on rats, but happily a cottage industry is trying to close the gap. And those researchers publish plausible data on rat behavior, no matter what the doubters tell you. So here are two tips. Skip the date palms. They’d clutter up your lawn, anyway. And skip plants that have a certain reputation for human behavior – e.g., tongkat ali – as rat physiology is similar.
Of course, rat problems may fall off if a bear takes up residence. My online searches for natural products to manage a bear’s mood have turned up only meals and pepper spray. Hmm.
Food for Thought
G.Z. Mukhtar et al., “Cinnamomun cassia, Ficus carica and Fumaria officinalis possesses aphrodisiac activity in male Wistar rats,” Annals of Experimental Biology, 3(3):14-17 (2015). https://www.scholarsresearchlibrary.com/articles/cinnamomun-cassia-ficus-carica-and-fumaria-officinalis-possesses-aphrodisiac-activity-in-male-wister-rats.pdf
U. Tijjani et al., “Aphrodisiac effect of aqueous stem bark extract of Ficus sycomorus on female Wistar rats,” Nigerian Journal of Basic and Applied Science, 26(1): 70-79 (June, 2018). https://www.ejmanager.com/mnstemps/97/97-1505123814.pdf?t=1551055379
S. Kotta, S.H. Ansari, and J. Ali, “Exploring scientifically proven herbal aphrodisiacs,” Pharmacognosy Reviews, 7(13):1-10 (2013). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3731873/
Circling-V ™ 