What is the Bumble Bee Recovery Program? Since the 1990s, bumble bee numbers have been plummeting, and that spells ecological disaster. Ninety per cent of all flowering plants — including most of the fruits and vegetables in your fridge — need these pollinators in order to reproduce.
Until the causes of these declines can be reversed, conservation breeding and reintroduction is the only way to safeguard at-risk bumble bees. Today, WPC is the only organization in Canada rebuilding wild bee populations through conservation breeding. Thanks to recent breakthroughs, we’ve figured out how to dramatically increase the number of queens we produce. Once they’re released into the wild, they can establish their own colonies, producing hundreds of pollinators to sustain the ecosystems around them.
Pollinators come in many different sizes and shapes. Bees, butterflies, moths, beetles… the list goes on! Even non-insects like bats and hummingbirds contribute to pollination. Despite this huge diversity among pollinators, the process of insect or animal-assisted pollination remains largely the same no matter who does it: pollen grains, which are the genetic material of male flowers, are transferred to the stigma of female flowers. Once attached to the stigma, the pollen grains are moved to the ovules, which are the genetic material of female flowers. The fertilized ovules then develop into seeds, allowing the plant to reproduce.
When we outline the process of pollination, it becomes abundantly clear that there is a deep relationship between the insects and animals that facilitate pollination, and the plants that rely on them to reproduce. It is estimated that approximately three-quarters of all plants in North America require an animal or insect to carry out their reproduction. But what do the pollinators get out of this?
Pollinators don’t pollinate out of the goodness of their own hearts (though they are all very sweet in our eyes!). The reality is that pollination, when done by an animal or insect, is an unintended consequence of the foraging behaviours of those animals and insects. Let’s take bees for example. From flowers, bees forage pollen, which acts as their source of protein, lipids and other crucial nutrients. They also forage nectar, which acts as their source of sugars. Bees visit male flowers for pollen, the pollen is dusted onto their bodies and is then transferred to the stigma of female flowers that they subsequently visit for additional nectar. In this regard, the relationship between pollinators and plants is a mutualistic transaction.
So, we know that many plant species need assistance from pollinators to reproduce, and we also know that these pollinators gain important nutrients when pollinating these plants. However, not all pollinators can pollinate as well as others!
Differences between insect groups affect both the variety of plants they can pollinate and how effectively they do it . Let’s first consider two insect groups, both pollinators, that are wildly different from each other: butterflies and bumble bees.
Butterflies use their incredibly long tongues to slurp up nectar from flowers, but their long legs keep their bodies away from the flower itself, making pollen less likely to stick to them (but they still pick up some!). Butterflies are also solitary insects, meaning they only need to forage enough to sustain themselves. On the other hand, bumble bees have shorter tongues and legs, resulting in their bodies coming into more direct contact with the flower. Bumble bees will often, very cutely, insert their bodies into flowers to reach pollen and nectar – I always love seeing a bumble bee’s bum sticking out of a flower while it feasts! The bodies of bumble bees are also extensively hairy, readily picking up pollen when they grasp onto a flower. Since they are a eusocial species (a species living in colonies with divisions of labour and cooperation) with an entire colony to care for, bumble bees will forage farther and longer than solitary species, packing their leg pouches full of pollen from many different plants before bringing it back to their nest.
Left: butterfly foraging from flower (by nola.agent on flickr, CC BY 2.0). Right: yellow-banded bumble bee foraging from willow catkins (by Tiffani Harrison). Notice the length of the butterfly’s tongue and the distance between its body and the flower! Contrast this with how close the bumble bee gets to the flower in order to access pollen and nectar. Though both of these organisms are considered pollinators, this one difference alone makes bumble bees much more effective. The yellow glob on the bumble bee’s leg is pollen that she’s packed to bring back to her colony. Bees must visit many flowers to collect this much, while butterflies only need to visit as many flowers as is necessary for their own nectar needs.
Let’s now consider two insect groups that are fairly close in their evolutionary relation. They are both bees (belonging to the family Apidae); both are eusocial, with colonies of workers that serve a queen; and both are generalist foragers that pollinate a variety of plants. However, only one of these two bees makes honey, and that same bee is both not native to North America and is incapable of performing buzz pollination…
That’s right! I am of course talking about our beloved bumble bees and the well-known honey bee. There are approximately 46 species of bumble bee native to North America, such as the yellow-banded bumble bee (Bombus terricola, listed as Special Concern in Canada) that we work with in our Bumble Bee Conservation Lab. Unlike the European honey bee (Apis mellifera), which was brought to North America by 17th century colonial settlers, bumble bees cannot produce honey. But what they can do is buzz pollinate – something that honey bees cannot do effectively.
So, what is buzz pollination, and why is it such a big deal that bumble bees can do it? Buzz pollination is a specific method of pollination that uses intense vibrations to dislodge pollen from flowers that hold onto it rather tightly. ‘Dislodge’ might not be as accurate to describe what is essentially a pollen explosion, with pollen grains forcibly bursting from the flower. This burst coats the pollinator’s body with enough pollen to ensure that it fertilizes a female of that same plant species if it is subsequently visited. The evolved reluctance to give up pollen is how these plants maintain energetic efficiency. If they readily give up pollen to less effective pollinators, like the butterfly example we discussed earlier, then they must waste additional energy to produce more pollen and hope that enough insects visit them to ensure their reproduction. Instead, plants that evolved the need for buzz pollination require only a single visit from a capable pollinator to be sufficiently pollinated. The trade-off for these plants is of course that not all pollinators are able to pollinate them.
A common eastern bumble bee buzz pollinating spotted knapweed (by Tino Breuer, a dedicated volunteer of our Pinery Provincial Park Community Science Program). Note the white specks covering the legs and head of the bee. Those are pollen grains that the bee dislodged through vibrations! The pollen burst from the flower and coated the foraging bee. Some pollen will be stored in the pollen pouch of the bee, but some will fertilize female knapweeds.
What makes a bee capable of buzz pollination is a combination of their anatomy and behaviour. On the anatomical side, it is the flight muscles that are involved in buzz pollination. Flight muscles are generally divided into two different types: direct flight muscles, which connect to the wings to make them beat, and indirect flight muscles, which connect to the inside of the thorax. When indirect flight muscles contract, the shape of the thorax itself begins to change, which in turn forces the wings to move up or down. Indirect flight muscles are larger and can generate a lot more force than direct flight muscles. It is this force, produced through the rapid contraction and relaxation of indirect flight muscles, that creates the “buzz” necessary for buzz pollination. All bees have indirect flight muscles; however not all bees have indirect flight muscles large enough to generate the force needed to expel the pollen from these flowers. Honey bees are technically able to vibrate their wings via their indirect flight muscles, but they cannot do so at a frequency as high as bumble bees, which makes buzz pollination quite difficult for them.
Left: a European honey bee visiting a flower (by Bernard Spragg on flickr, CC0 1.0). Right: an American bumble bee foraging from viper’s bugloss (by Cole Blair). The larger bodies of bumble bees, particularly in the thorax, allows for bigger and stronger indirect flight muscles compared to honey bees. This allows bumble bees to buzz pollinate a wider variety of plants.
The foraging behaviour of honey bees also makes them ineffective as buzz pollinators. As with most foraging animals, a bee will seek out meals that are easy to access, while avoiding meals that are hard to secure. Honey bees may shake loose some of the tightly-held pollen from these flowers, but not much, and often not enough to make up for the time and energy spent acquiring it. As such, honey bees will often avoid flowers that require buzz pollination in favor of flowers that do not. In contrast, bumble bees will happily seek flowers that need buzz pollination, despite the energetic toll. This is because not many other insects can access that pollen, so the likelihood of securing a big meal is quite high!
Buzz pollination is critical due to the sheer number of plants that require it. Many have wild and cultivated varieties, such as blueberries, cranberries, tomatoes, pumpkins, zucchinis and potatoes. Wildflowers that need buzz pollination include lupins, nightshades, mints (including catnip!), orchids and many others. All of these plants – and, by extension, all of the animals that rely on them, including us – need buzz pollinators. Several solitary native bees including mining bees, digger bees, sweat bees and leafcutter bees can also perform buzz pollination, but none do it quite as well as the bumble bee!
And they need our help!
While honey bees often take the spotlight due to their role in agriculture and honey production, they are not native to North America. Some headlines tell us that honey bees are in decline, however as an agricultural animal, they are not at risk of extinction in Canada. In fact, honey bees do so well that they often outcompete our native bees for food and can spread diseases to wild populations, especially when in high densities.
Although some bumble bees are also used commercially in agriculture, such as the common eastern bumble bee (Bombus impatiens), the unfortunate reality is that about a quarter of North America’s bumble bee species are in decline. Without them, our delicate ecosystems, along with our food production, are jeopardized.
We all want to save the bees, but it is important that the bees we save are actually in need of saving. To help native bees around you, consider planting pollinator-friendly native flowers, leaving parts of your property unmanaged, leaving the leaves in your yard, and please refrain from spraying pesticides.
Two bumble bee species federally listed as Endangered in Canada: the rusty-patched bumble bee (left) and the Ashton cuckoo bumble bee (right) (photos by Sheila Colla). The rusty-patched has not been recorded in Canada since 2009, and the Ashton cuckoo has not been recorded in Ontario since 2008. Five other Canadian species and subspecies have been assessed as either Special Concern or Threatened by the Committee on the Status of Endangered Wildlife in Canada.
What you need to know:
What you can do to help: plant native flowers and allow parts of your outdoor space to naturalize!
We need your help
