Why bees choose the same flowers again and again

In spring and summer, gardens explode with floral variety. Yet, watch a bumblebee closely, and you’ll notice something strange. Despite the buffet of colors and scents, the bee often sticks to one flower type per trip.

It might move from one lavender bloom to another, ignoring daisies right beside them. This selective foraging, called flower constancy, has intrigued naturalists for centuries.

Charles Darwin proposed a simple explanation. He believed bees chose the same flowers again and again because switching would require more memory effort. This idea held weight for a long time. After all, remembering different flower shapes, colors, and nectar rewards does demand mental work.

But new research from the University of Tsukuba offers a more refined view. It shows that bees don’t just aim to avoid thinking too much. They make smart, strategic choices based on their surroundings.

How bees choose flowers

The study, led by Kentaro Takagi and Kazuharu Ohashi, shows that bees weigh two key costs: how much time it takes to remember a flower and how far they must travel to reach the next one. Their behavior results from balancing these two demands.

“We found that pollinators do not simply avoid memory effort but rather choose a strategy that minimizes the total cost of memory use and travel,” explained Professor Shoko Sugiura.

This shifts our understanding away from passive behavior. Flower constancy is not just about bees lacking the mental power to switch. It’s about making the best of what they have – adapting their strategy in real time as flower arrangements change.

Why bees switch flowers

The researchers tested this theory using artificial flowers in controlled indoor cages. Some flowers had high color contrast – blue and yellow. Others had subtle differences – yellow and golden yellow.

They also varied how flowers were arranged. In some cases, flower types were thoroughly mixed. In others, each type was grouped in clear clusters.

In mixed arrays, bees faced a choice. If they kept visiting only one species, they had to fly farther between flowers. This raised travel time. But if they switched flower types, they had to recall a different memory. The bees often chose to switch, especially when flowers looked similar and the memory cost was low.

In this setting, bees behaved like economists. They balanced the time spent flying with the time spent thinking.

When travel costs went up, they tolerated memory costs. When the mental load increased, they minimized flights. The shift in constancy wasn’t random. It was logical.

Similar flowers make switching easier

One striking observation came from the trials involving subtly different flowers. When bees foraged among yellow and golden yellow blooms, they treated them almost as one type.

Even though bees can tell these colors apart, the difference wasn’t strong enough to require separate memories. This helped them switch more freely and saved time.

But memory plays a second, subtler role. As bees visit one flower type repeatedly, they begin to forget the other. The information in short-term memory fades back into long-term storage. This “memory decay” increases the retrieval cost if the bee later wants to switch.

“Pollinators are more flexible than previously assumed. They assess costs and make efficient choices,” said Professor Takuya Kameda.

In clustered arrays, this decay worked in favor of constancy. Bees stuck to one type, moved short distances, and avoided memory shifts. But in spaced-out arrays, decay had the opposite effect. By the time a bee reached the next flower, memory had already faded. Switching became easier.

Bees adapting smartly

To test their ideas further, the researchers built a computer model. They simulated bees moving through different flower arrangements. In these simulations, the experts removed memory retrieval costs. The model only considered how bees would behave if they cared only about distance.

The result matched real-world bee behavior in several cases. Especially in arrays with low visual contrast or large spacing, real bees acted like the simulated ones.

This confirmed that travel distance alone can push bees to switch. Only when flowers were tightly packed and visibly different did memory costs dominate and lead to stronger constancy.

These results challenge the traditional view that flower constancy is just about bees being creatures of habit. It is not about a mental cap. It is a trade-off. The bee calculates, perhaps not consciously, but clearly effectively, the best path through a sea of choices.

Why this matters for plants and evolution

This new understanding has important consequences for plants, too. When bees switch flowers frequently, pollen may land on the wrong species. That’s bad news for reproduction.

So, many ecologists thought that having flowers look different from neighbors was a strong evolutionary pressure. But the data haven’t always backed that up. Some flower communities are highly diverse. Others are not. Sometimes, co-flowering plants look nearly identical.

The findings from this study explain why. It’s not just about color differences. It’s about spatial layout. If different species grow in patches, bees will stay constant regardless of color. If they grow all mixed up, bees will switch more unless there’s a strong visual cue to stop them.

So, flower constancy isn’t fixed. It’s flexible. And that flexibility changes the selective pressures plants face.

Mixed communities may need stronger visual traits to keep bee visits clean and efficient. Clustered species may rely more on positioning than petals.

What bees teach us about smart foraging

Ultimately, this research gives us a new way to look at bee intelligence. These insects make highly effective decisions. They don’t act from instinct alone.

The behavior of bees is shaped by their environment, their memory, and their spatial awareness. They save time and avoid waste. They change plans when the layout changes. That’s not limitation – it’s strategy.

Bees teach us that loyalty to a single flower isn’t about habit. It’s a calculated choice in a world full of options.

The study is published in the journal Functional Ecology.

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