Bridging the Bumblebee “Hungry Gap”: Innovative Strategies for Pollinator Planting (Ep. 43)

In the vibrant tapestry of our ecosystem, bees play an indispensable role. Yet, these industrious pollinators face tremendous challenges, particularly during critical periods of their life cycles. Today we discuss the “hungry gap,” a pivotal time in early spring when bumblebee larvae face a scarcity of resources. The term refers to a challenging period in late winter and early spring, from March to April, when bumblebees struggle to find enough protein-rich resources. 

Dr. Matthias Becher is an Ecological Modeller and Affiliate at the Environment and Sustainability Institute, University of Exeter. You can read the study we discussed here and learn more about the bee computer model Matthias’ and his colleagues used to study bumblebee colonies here.

Good to know

Matthias mentioned the importance of adding early-flowering plant species to seed mixes to support bumblebee queens during this vulnerable time. Dr. Sara Leonhardt talked about these pollinator seed mixes in episode 31 where we looked closely at the nutritional needs of bees. 

Transcript

[00:00:00] Welcome to The Bee’s Knees. I’m your host, Jacy Meyer. The Bee’s Knees is a podcast wild about native bees. Wild and native bees are under threat worldwide. In each episode, we look at actionable things we can do to support these adorable little guys whose pollination work is crucial for maintaining biodiversity.

Thanks for being here.

It’s autumn in the Northern Hemisphere, but it’s never the wrong season to talk about what bees need when. Today, we’re looking at the seasonal needs of bumblebee colonies and how resource scarcity during critical periods can dramatically affect their survival and queen production. Dr. Matthias Becher shares with us his findings on the hungry gap, a crucial time in early spring when bumblebee larvae face a shortage of protein rich resources.

Matthias is an ecological modeler and affiliate at the [00:01:00] Environment and Sustainability Institute at the University of Exeter. We kicked off our conversation by talking about pollinator planting. So pollinator planting is basically the idea to provide resources to pollinators, for example, bees, but it can also be hoverflies, butterflies, and other insect pollinators.

And pollinator planting is then the idea to have a number of flowers around. More or less at the important times of the year to support certain pollinator species. So you used the agent based model, Bee Steward, with two bumblebee species. Can you tell me about this model and why you chose these two species for your research?

So this is a quite complex computer model where we basically simulate the life cycle of bumblebees. So we simulate what the individual bees are doing, where they are going to forage, how much nectar and pollen they bring [00:02:00] back, but we also simulate the development of the colonies. And the how the population will grow or decline over time, depending on the resources available in the landscape.

And we chose Bombus terrestris, so the buff tailed bumblebee, and Bombus pasquorum. And Bombus terrestris is a very common bumblebee species, relatively large. It has a short tongue. It emerges early in the year. So the queens emerge early in the year and they form relatively large colonies. And Bombus pasquorum emerges a little bit later in the year.

They have longer tongues and smaller colonies. So they’re a bit contrasting types of bumblebee species. And we were interested in how they perform and how they differ. So you identified a critical hungry gap for bumblebees in March and April. Can you elaborate on what this gap entails and how it affects the bumblebee colonies during this [00:03:00] period?

Yeah, maybe I quickly explain what we were actually doing. So we were running the model in a simplified setup. So in a landscape that always provides nectar and pollen and Then we added a two weeks gap where all the resources were artificially removed. And then we looked when this hungry gap or forage gap had the most impact on the population over time.

So we basically started the hungry gap either on the 1st of January, on the 14th of January and so on throughout the year. And we then looked when it has had the most negative impact on the bumblebee population and the results clearly show that. Obviously, in winter when there are no bumblebees around, obviously the forage gap doesn’t matter because bumblebee queens are in hibernation.

But the most critical period of time was in late winter, early spring, [00:04:00] around March, April, maybe early May. And that was the period when the colony was in its founding stage. So in contrast to honeybees, which overwinter as a colony, the bumblebees only overwinter as, or only the queens overwinter. So the queen then, in spring, needs to found her own nest, she needs to find a nest place, and then collects

resources, nectar and pollen before she then can raise a first generation of worker brood. And this founding stage seems to be really a critical point in the development of the colony where they really rely on resources. So what do you think are the broader implications of this finding for bumblebee populations and then thinking about pollinator conservation efforts?

So I think the most interesting result is that additional resources are most important during the founding phase of the colony. And that is [00:05:00] actually when you don’t see a lot of bees flying around. So that is the phase when mainly the queens are around and foraging. So maybe you don’t really notice that there are bumble bees already around, but that’s really the critical point where they need.

resources. And later when the colony is growing, when there’s a worker generations as adults helping the queen to raise the brood to collect nectar and pollen, then the colony is already more robust and can better deal with forage gaps and lack of resources. So given the ongoing global decline in pollinator populations, where would you like to see the research go in this area?

Um, so For my personal interest, I’m very much interested in, on the one hand, the foraging decisions and foraging activities of the bees on the individual level and how they decide actually where they go to, which plants they [00:06:00] go to, when they think, okay, this plant doesn’t provide enough nectar resources to another one, which plant species they choose.

So that would be interesting for me, but Also important would be to fill some dramatic data gaps we have on nectar and resource availability. So nowadays it’s, we are quite good at mapping areas and define which habitat types there are. What is growing there, but it’s hard then to link this to actual nectar and pollen production of that area, because for that we would actually need to know which exact species is there and what is nectar and pollen production basically in each flower, and that’s, of course, it’s extremely difficult to get, so at the moment it still needs to be done manually, so people need to get out At the right time, extract nectar from the flowers, which is very tedious and time consuming, collect the pollen and analyze the results.

So more data on resource [00:07:00] availability, I think that would really help to improve our model predictions. Do you have any recommendations for policymakers or conservationists or even you and I to develop more effective pollinator protection strategies? So what we actually found is that seed mixes, which should provide nectar and pollen resources to the bees, often miss those early flowering plant species.

And one recommendation from that study would be really to add early flowering species to those seed mixes. The most interesting and most important result of this study is that according to our study, the bumblebees need resources most when they’re in the founding phase of the colony. So this is basically when you have the queens You can basically compare them to single moms having to care for the family, rear the brood, but at the same time have [00:08:00] a job and collect nectar and pollen.

So they are super busy with all the work. And also it’s then important to not only provide in general resources, but they should also be relatively close to the colony because Foraging is quite risky, and the more time the bees need to spend outside, fly to a place where there is forage available, fly from flower to flower to collect nectar and pollen, the more time that takes, the higher is the risk that the bee might die because of a predator, because she gets lost, loses orientation or whatever.

So having high quality food sources close to the colony is also really important. So why do you do what you do? Why bees? Why bees? Um, well, when I started to work on bees, that was when I started my PhD and I wanted to work with social insects. To be honest, I would have preferred ants, but then I got a PhD with bees and in hindsight, I [00:09:00] would say that was lucky and they’re just super cool and interesting and exciting insects.

My thanks to Matthias for sharing his work on the critical relationship between pollinator planting and bumblebee survival and stressing the importance of addressing the early spring hungry gap in conservation efforts. Please consider adding early blooming plants into your gardens and make sure you have some food resources scattered about

so these hardworking queen bees don’t need to fly so far. Thanks as always for listening to the Bees Knees. I appreciate your support and thanks for sharing the Bees Knees buzz. Together we can make a difference. Until next time, be early.