Wasp moms manage multiple nests with remarkable memory

Digger wasps exhibit remarkable memory skills when managing their nests. These wasps create separate burrows for each egg, storing food inside and returning after a few days to provide more.

They can remember the locations of up to nine nests simultaneously, despite the chaotic surroundings filled with hundreds of other females’ nests. The wasps rarely make mistakes, ensuring that each offspring receives adequate nourishment.

Digger wasps manage multiple nests

Mother wasps feed their young in age order, adjusting the sequence if one larva dies.

They can also delay feeding larvae that received more food during the first visit. This intricate scheduling prevents starvation and ensures all larvae get sufficient food.

“Our findings suggest that the miniature brain of an insect is capable of remarkably sophisticated scheduling decisions,” said Professor Jeremy Field, from the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“We tend to think that something so small couldn’t do something so complex. In fact, they can remember where and when they have fed their young, and what they fed them, in a way that would be taxing even to human brains.”

Episodic memory in wasps

Humans use episodic memory to recall past actions and adjust future plans. Professor Field suggests that wasps may use a similar mechanism to remember where and when they last fed each larva.

Although the exact process remains unknown, the study indicates that these wasps can track multiple nests, the food given, and the timing of each feeding.

Caterpillar hunting and feeding strategy

Digger wasps hunt caterpillars on heather plants, paralyzing them before placing them in burrows with eggs. The larva consumes the caterpillar as its first meal.

Mothers then seal the burrow entrance and leave to either start a new burrow or continue feeding existing offspring. They return after two to seven days to check on the larvae.

If a larva is dead, the mother lays a new egg and reorders the feeding schedule.

Navigating hundreds of nests

Despite nesting in nearly featureless sand with hundreds of other nests, mother wasps maintain exceptional spatial awareness.

They use visual landmarks like stones to locate their nests with impressive accuracy. The study recorded just 1.5% of 1,293 food deliveries going to the wrong nest, emphasizing the precision of their navigation skills.

The researchers also tested the wasps by swapping caterpillars as mothers prepared burrows.

Wasps given larger caterpillars waited longer before providing more food, indicating a flexible feeding strategy based on larval needs. This adaptability helps manage resources effectively and supports the survival of the young.

Wasp memory, nests, and scheduling

Professor Field noted that memory is energetically expensive, requiring neural machinery to store and process information.

While many lab-based studies explore memory in controlled settings, this study demonstrates the ecological relevance of memory in the wild, showing why natural selection may have favored these capabilities.

The researchers used various experiments to explore wasp memory and scheduling. One experiment involved replacing food items in nests, testing whether wasps adjusted feeding schedules based on food size.

Mothers given larger prey items delayed further feeding, initiating new nests sooner. This behavior allowed them to increase reproductive output without compromising larval survival.

How wasps adjust after losing a nest

Mothers could remember up to nine active nests and adjust feeding schedules without revisiting nests.

However, when larvae died, mothers replaced them with new eggs, moving these nests to the back of the feeding order. This strategy minimized energy loss and prevented resource wastage.

Fieldwork at Witley Common, UK, revealed that digger wasps evolved cognitive strategies to counter parasitism and food scarcity.

Parasitic flies pose a significant threat, laying eggs on wasp larvae. To minimize exposure, mother wasps avoid revisiting nests unless parasitism risk is low. This reduces the chances of parasites accessing vulnerable offspring.

Additionally, food scarcity prompted wasps to develop efficient nest management. By remembering up to nine nests, mothers allocate food based on larval age without resampling, conserving time and resources.

Evolution of cognitive traits

Researchers suggest that these memory and scheduling abilities may have laid the foundation for social behaviors seen in more advanced insect lineages.

Managing multiple offspring, tracking nest locations, and adjusting feeding schedules align with the caregiving patterns observed in social insects like ants and bees.

The study highlights how ecological pressures can drive the evolution of complex cognitive traits even in insects with tiny brains.

The study is published in the journal Current Biology.

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