Gerbils haven’t taken to the air and started buzzing, but scientists now have
evidence that they spread pollen as bees do.
In southern Africa, the hairy-footed and the short-tailed gerbils poke into a
ground-hugging lily, slurping nectar and emerging dusted with pollen, says Steven
D. Johnson of the University of Natal in Petermaritzburg, South Africa. In one
sandy area tested, the gerbils do most of the pollination for the plant, his team
reports in the October American Journal of Botany. In rockier terrain, at least
two other rodents transfer pollen, too.
Bats are the champion pollinators among mammals, but scientists have reported that
at least 59 species of nonflying mammals, mostly marsupials and primates,
pollinate plants in 19 families. Only three plant families, none closely related
to lilies, have confirmed rodent pollinators, Johnson says. Yet the lily flowers
resemble others that rodents pollinate. “The heart of the story is that we got the
idea [of testing for rodent pollination] from the similarities,” he says.
The lily, Massonia depressa, grows in the dry region called the Succulent Karoo.
In the same family as garden-variety hyacinths, the African plant forms two large,
flat leaves. “Imagine water lily leaves spread on the ground,” says Johnson.
The flowers, tufts clustered in a bristling pom-pom, also sit at ground level.
Starting each evening, they secrete gobs of nectar as thick as jelly.
The nectar’s accessibility for nocturnal rodents caught the researchers’ attention
because some Protea shrubs pollinated by African mice also bear low flowers. Like
the Protea, the lily produces unusually sturdy blooms, which withstand rodents’
verve.
The researchers assumed that they were looking for a nighttime visitor, so they
set soot-covered cardboard and catch-and-release traps near blooms. The cardboard
picked up rodent paw prints, and the traps caught three mouse and two gerbil species. The five gerbils–classified as Gerbillurus paeba and Desmodillus auricularis–belong in sister genera to the one that includes the common pet.
When Johnson checked his captives’ snouts, 7 of 13 animals carried telltale lily
pollen. The researchers released the trapped gerbils into an enclosure around a
plant, and the rodents dove for nectar, leaving the flower intact but their snouts
gilded with pollen. “They prize the flowers open with their front legs and push
their faces in,” Johnson says.
In another field test, researchers covered flowers with mesh that admits insects
but not gerbils and mice. Seed number plummeted in these caged lilies compared
with unencumbered plants.
The lily work stemmed from the notion that unrelated flowers converge on rodent-attracting traits, says Johnson. However, he acknowledges that such patterns have
proved controversial. Challengers have published long lists of disparate
pollinators visiting flowers supposedly specialized for only some of them.
Finding which flower visitors pollinate well and which just loiter needs a lot
study, says Susan Carthew of the Adelaide University in Roseworthy, Australia.
Despite all the reports of nonflying mammal pollination, Carthew says, “we really
don’t know a lot about it.”
