About 87% of flowering plants are pollinated by animals. These include wild flowers and those used by people for food and medicine. Thousands of bee species are pollinators for a huge variety of plants, and many other insects – flies, wasps, beetles, butterflies – are all vital for the transfer of pollen from one flower to another.
Plants and animals have been co-evolving for millions of years. Some flowers are generalists and are visited by many species, while others are specialists, having adapted to co-exist with specific animals.
So what species are some of nature’s more unusual pollinators?
They're often overlooked, but about 9% of mammals and birds are thought to pollinate plants.
Most recently, Cape grey mongooses and large-spotted genets, which are both carnivores, surprised researchers in South Africa when they were captured on remote video visiting – and pollinating – sugarbush plants (Protea).
The scientists’ findings are published in the African Journal of Ecology.
“The fact that they’re part of the Carnivora [an order of mammals that mainly eat meat] was surprising,” says Dr Sandy-Lynn Steenhuisen, a researcher from the University of Cape Town, who worked on the study. “They’re [usually] going after lizards and frogs and insects – not really flowers.”
The stubby plants’ open bowls of nectar – which give off a cheesy, sour-milk like perfume – are frequently visited by rodents. Mongooses and genets are probably only occasional visitors, but these larger mammals might help spread the pollen much further across their expansive ranges.
The discovery that these meat-eating mammals help pollinate sugarbush plants comes not long after news that, around the world, mammal and bird pollinators are heading towards extinction.
Exactly what attracts mammals to these plants still needs to be investigated, says Dr Steenhuisen.
But the nectar is probably a “sweet treat” for the otherwise carnivorous mongooses and genets. “They don’t rely on [nectar]”, she explains. “It’s kind of like offering candy to a kid.”
Unlike baboons, which also love nectar but which simply pick the flower, take a bite and throw it away, genets and mongooses definitely appeared to be pollinating the plants.
“On the cameras we could actually see their faces covered in pollen – they are definitely picking up pollen.”
“The [flowers’] stigmas actually just stick straight up. So anything pressing against the flower will deposit pollen.”
Another smaller South African mammal with a taste for nectar is the Cape Rock sengi (Elephantulus edwardii) – a member of the strange-looking elephant shrew family.
They have been shown to prefer nectar over other food, even though they are primarily insectivores.
The animals – which are more closely related to elephants than to shrews – extract the sweet liquid from flowers of the Pagoda lily plant (Whiteheadia bifolia) in rock crevices with their long, slender tongues while their faces become covered with pollen.
I have always loved the thought of this intimate relationship having been developed between the iconic traveller’s palm and the black lemur
While many ground plants benefit from small mammals’ pollination, some flowering trees rely on similar relationships with tree-dwelling or flying mammals.
One of these animals is the lemur – which is among the world’s largest known pollinators.
Black lemurs (Eulemur macaco) in Madagascar have been recorded dipping their paws into the flowers of the traveller’s palm and other trees to extract nectar, or pushing their snouts into the centre of flowers to drink from nectar chambers. They also lick pollen from plants’ stamens.
Anne Yoder, director of the Duke Lemur Centre in Durham, US, says: “I have always loved the thought of this intimate relationship having been developed between the iconic traveller’s palm and the black lemur.”
The ruffed lemur (Varecia variegata) is thought to feed at traveller’s palms too. And one study suggests the tree is specialised for large, non-flying animals. Its large flowers are surrounded by tough leaves that take strength to open, and they provide copious nectar to sustain a large animal.
Bats are probably the best known mammal pollinators. Hundreds of plants rely on these busy, flying nectar lovers to spread their pollen at night, especially in tropical and desert environments.
Bat pollination, known as chiropterophily, occurs in flowering plants including cocoa, mango, guava, banana and agave – the plant used to make tequila. And the baobab tree relies almost solely on bats for pollination. As the furry mammals seek a sugary nectar drink, their faces become covered in pollen, which they transfer to the next flower.
Bats are lured in to these large, pale flowers that open at night, not by how they look, but by the fruity smell they give off. Some species show extreme adaptations for nectar collections, such as the tube-lipped bat in Ecuador, which is the owner of an extraordinary tongue that’s over one and a half times its body length, used for reaching into deep petals.
In reptiles, around 40 lizard species are known pollinators, including skinks, geckos and wall lizards. This type of pollination is usually associated with island ecosystems, where resident reptiles tend to include nectar and fruit as part of their diets.
In Fernando de Noronha, an archipelago off northeast Brazil, the 25cm-long Noronha skink or “little dragon” (Euprepis atlanticus) laps nectar collected in the base of flowers in the leguminous mulungu tree.
Researchers suggest the lizard – which enjoys a varied diet that also includes animal corpses – is attracted to the liquid for its energy-giving diluted sugars and water content, possibly because the island has no natural fresh water during the dry season.
As the lizards lap up nectar, pollen from the flowers’ anthers (the part of the stamen where pollen is produced) sticks to their scales. Nectar is probably a bonus for this species as there is usually plentiful other food available.
In birds, hummingbirds are famed for their pollinating role but perhaps more surprisingly, parrots visit and pollinate flowers too.
The swift parrot (Lathamus discolour) depends on flowers from the Tasmanian blue gem tree (Eucalyptus globulus) – migrating hundreds of miles across Australia to breed around the trees in Tasmania.
The colourful birds have evolved to become specialist nectar and pollen feeders and are thought to be more effective pollinators than insects at these trees, transferring large amount of pollen on their head feathers and bills.
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Swift parrot (Lathamus discolor) by Ernst Vikne.