Biology subjects

Burrow, J. K.

Publications and source records attributed to Burrow, J. K..

3 recordsLinked to original sources

bioRxiv2025

Bees attend primarily to costs, not benefits, to avoid exploitation by floral mimics

Animals are expected to weigh costs and benefits when making foraging decisions. Flowering plants often offer floral food rewards to pollinators, but also frequently deceive pollinators into visiting without providing rewards. Although floral mimicry, in which rewardless flowers mimic rewarding (model) flowers is common, it remains unclear whether pollinators evaluate the relative costs and benefits of visiting each. Using a signal detection theory (SDT) framework, we investigated how bumble bee decisions respond to experimental manipulations of costs and benefits within an intersexual floral mimicry system in which unrewarding female flowers imperfectly mimic pollen-rewarding male flowers (models). Using a fully factorial design, we increased the cost of visiting mimics (by adding quinine), increased the benefit of visiting models (by adding pollen), increased both simultaneously, and made no changes (control). As predicted by SDT, increasing mimic costs led to a conservative bias: bees made more correct rejections, but fewer correct detections. Contradicting SDT predictions, enhancing model reward did not elicit a liberal bias and decision performance remained unchanged. Our findings suggest that bees prioritize avoiding costly errors under uncertainty, even when this limits potential gains. Such conservative foraging decisions may help stabilize deceptive systems by allowing mimics to persist despite moderate costs.

animal behavior and cognition↗

bioRxiv2025

Take it or leaf it: bees learn leaf shape as a cue when flower color is easily learned

Over a century of research has demonstrated that pollinators, such as bees, associatively learn diverse flower cues, including tactile, visual, and olfactory cues, to find food rewards. However, floral cues are not always reliable, as flowers of different plant species often differ in terms of the qualities of their food rewards, even when flower types resemble each other. At the same time, some non-floral traits, such as leaf shape, differ reliably among plant species and might be associatively learned by bees to improve foraging success. In this laboratory study, we tested whether generalist bees (Bombus impatiens) can (1) associatively learn differences in leaf shape to discriminate rewarding from unrewarding flowers and (2) rely more on differences in leaf shape when a flower color cue is harder to discriminate. We therefore assigned bees to either of two treatments: in one treatment, rewarding and unrewarding artificial targets ( flowers) differed greatly in petal color, and in the other treatment, they differed little; each treatments targets differed in leaf shape in the same way. As expected, bees learned significantly faster when flower petal colors were more dissimilar and thus relatively easier to discriminate. These bees also learned and recalled the correct combination of petal color and leaf shape. Yet when petal colors differed relatively little, bees had a much harder time learning petal color and did not show evidence of having remembered leaf shape. Our results demonstrate that leaf shape is a cue that foraging bees can learn to associate with a pollen food reward. However, leaf shape may be learned secondarily to, or only in combination with floral cues (such as petal color). We discuss evidence of compound learning and overshadowing and implications of our results for pollinator-mediated selection on non-floral plant traits.

animal behavior and cognition↗

bioRxiv2024

One for the road: Bumble bees consume pollen at flowers

Bees are the primary consumers of pollen in many ecosystems, but pollen consumption by adult bees is rarely studied, leaving a gap in our understanding of the nutritional ecology of collective foraging and pollination biology more generally. For example, while eusocial bees feed upon pollen from colony stores, whether they also consume pollen directly from flowers to meet their own needs or to assess its quality for the broader collective is unknown. We therefore captured wild bumble bee colonies (B. bimaculatus and B. griseocollis) and tested whether individual workers consumed pollen directly from flowers in a lab-based foraging assay. After confirming presence of floral pollen in worker crops (i.e., consumption at flowers), in a field setting we tested alternative hypotheses for the function of this behavior using information about the composition, abundance, and diversity of pollen found in the crops vs. pollen baskets of three species of pollen- and nectar-foraging bumble bees (Bombus bimaculatus, B. griseocollis, and B. impatiens). Consistent with the hypothesis that consuming pollen at flowers reflects sampling, total pollen quantity in crops was consistently smaller than in pollen baskets, and basket pollen tended to be a subset of that found in crops. Further, pollen foragers consumed more and different kinds of pollen than nectar foragers. Pollen consumption at flowers is thus unlikely to be purely incidental, or to substantially benefit workers nutritionally. Instead, consuming pollen directly from flowers likely allows foragers to quickly assess pollen quality before collecting it to feed the colony as whole. SIGNIFICANCE STATEMENTWhile nectar-collecting bees are classic models for the study of foraging behavior and plant-pollinator interactions, little is known about how bees assess pollen while foraging. Pollen is a critical source of protein and lipids, offered by many plant species alongside or instead of nectar. Though variation in pollen macronutrient content and secondary chemistry affect bee reproductive performance and health, whether and how foragers evaluate pollen quality is not known. We show that foraging worker bumble bees consume pollen at flowers and suggest this behavior may allow them to sample its nutritional quality. This sheds new light on the nutritional basis of plant-pollinator interactions and adds to our understanding of how bees regulate their collection of this critical resource.

animal behavior and cognition↗