The birds do. Also bees. Especially the bees.
But common rats pollinating plants? In a study published in June in the journal Ecology, two researchers report that in Colombia, brown rats, the same ones that feast on garbage and steal pizza slices in cities around the world, may be the main pollinator of feijoa in urban settings. plant, which produces a fruit that is widely consumed in the country.
“I was very surprised because, at first, I knew the stories but never really paid much attention,” said Carlos Matallana-Puerto, a plant biologist at the State University of Campinas in Brazil, whose comments were translated by João Custódio Fernandes Cardoso. , co-author of the report. “Then when I started studying, I started to get excited because I started to realize that the thing makes sense.”
In Matallana-Puerto’s hometown of Duitama, Colombia, residents—including her father and brother, and even the elderly woman who lives down the street—had long reported seeing typically nocturnal rats walking and perching on the trees in broad daylight.
But when he began studying the science of pollination in college, the stories took on a new meaning: Could the rats have been pollinating the trees?
It wasn’t a leap to wonder if rats could be pollinators. It is estimated that 343 species of mammals are pollinators. Bats, which some people call “winged mice,” are well known for pollinating bananas, avocados, mangoes, agaves, and durians. Elephant shrews, honey possums, lemurs and other rodents have also been seen helping plants perform their reproductive tasks.
To test his hypothesis, Mr. Matallana-Puerto did what any good naturalist would do: he observed and observed that rats were attracted to feijoa plants. They produce a sweet fruit that tastes like a mixture of pineapple and guava.
From the vantage point of his bedroom terrace, in the same neighborhood his grandmother once lived in, Mr. Matallana-Puerto surveyed 22 feijoa trees with a camera and binoculars to see what rats and any other visitor and if they could pollinate the plants.
From his bedroom window, Mr. Matallana-Puerto saw that the brown rat accounted for 88 percent of all animal visits to feijoa flowers. The birds visited only a handful of times during their 60 hours of observation.
If the rats are pollinating feijoa plants, their behavior is a bit unusual. Most pollination by rodents occurs at night at ground level, on plants that have strong odors and offer nectar as a reward.
In Colombia, feijoa flowers are found in the treetops, without nectar or scent; instead, the rats feed on the petals, feeding during the day when the flowers are open and fertile. This may be the first case of rat pollination in which flower petals are the draw, according to the scientists.
“They are sweet,” Dr. Cardoso said of the petals.
Importantly, the rats do not appear to damage the reproductive parts of the flowers when they feast on the fleshy white petals. Instead, the rodents rub against the dozens of scarlet stamens, which carry pollen that could then stick to their fur coats before being transferred to another feijoa tree.
“It’s very unusual for a plant to have petals as a resource, and it’s quite surprising that rats realized they’re nutritious,” said Jeremy Midgley, emeritus professor of biology at the University of Cape Town in South Africa, who was not involved. in the study.
However, Dr. Midgley had some reservations about the hypothesis.
While the research showed that the rats did visit the plants, there was no information on how many of the flowers produced fruit as a result, he said. “It would be great if they had shown that rats really work.”
When Mr. Matallana-Puerto and Dr. Cardoso reviewed the scientific literature, they found earlier reports that the feijoa plant was pollinated by birds. The researchers hypothesize that in the city, rats may be more frequent guests due to reduced bird activity, highlighting how pollination systems may change with urbanization.
The story of the rats and feijoa found in the city, and possibly elsewhere, is an unlikely love affair: neither is native to Colombia.
Rats arrived from Europe, probably hundreds of years ago as a result of colonization; feijoa trees spread north from their native Argentina, Uruguay, and Brazil.
“And these two met in Colombia,” said Dr. Cardoso. “So, they don’t co-evolve. They do not share a natural history. But they meet, and their morphology, physiology and behavior allow them to interact.”