As It Happens

New study shows when it comes to bee tongues, size matters

It's a bit of buzzkill. A new study shows that the tongues of alpine bumble bee are getting shorter as a result of climate change, leaving the bees, and deep flowers, longing for more.
Queen bumble bee foraging on Oxytropis sericea flowers on the alpine tundra of Pennsylvania Mountain. (Candace Galen/University of Missouri)

Evolution is leaving alpine bumble bees a little short-changed.

Recent studies suggest that the population of long-tongued alpine bumble bees is in decline. To better understand why, a team of researchers studied two species of the bees in Colorado. They measured changes in the bees' tongue length, and found that their tongues have been getting shorter over the past five decades.

Nicole Miller-Struttmann is a biology professor at SUNY College at Old Westbury in New York. She is the lead author on the study, which is published today in Science Magazine. As she tells As it Happens host Carol Off, the change is significant.

"We found, on average, about a 24 per cent decrease in tongue length, which is pretty substantial," says Miller-Struttmann.

Tongue length is important for bees because they use their tongues to get food, which gives them the energy to fly and collect pollen. She cites changes in flower species as a reason for the decline in bee tongue length.

"We've seen declines in flowers on Pennsylvania Mountain at about 60 per cent. And with that, these bees have to now visit a whole bunch of different kinds of flowers because they need to visit any flower they can in order to get resources. Whereas in the past, they could specialize, and they could say 'ok, you're my favourite flower. I get everything I need from visiting you. You have the most nectar', and then they'll specialize on those flowers."

The bees used to prefer deep flowers, such as clover, which require a longer tongue to extract all the nectar. But as clover has declined due to warming temperatures, the bees now feed on a diversity of flowers, including shallow flowers, which could be a reason for the shortening of their tongues.

But the change in tongue size does have some benefits.

"Long tongues are expensive. If you think about the length of these tongues, in one species they're about 8 mm long, and a bee isn't that big, so that's a pretty large proportion of the body size. So that takes a lot of resources to grow a tongue that big. So if there isn't any major benefit to having that long tongue, then it'd behoove the colony to have bees with shorter tongues that can visit the greater diversity of things that are out there."

Miller-Struttmann says it is encouraging that the bees are changing to cope with the changes in their food supply, but says "what the future holds, remains to be seen."


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