The astonishing memory of monarch butterflies

You wouldn’t think it to look at them, but insects have impressive cognitive abilities. Long-term memory, number skills and facial recognition are just a few examples. Among Lepidoptera, research has demonstrated that certain moths remember their lives as caterpillars.¹What about monarch butterflies? What do we know about their cognitive capacities?

Memory testing

Scientists have taken an interest in this question in recent years. They’ve attempted to assess the ability of migrating monarchs to retain both olfactory and visual information.² So that these cognitive skills could be observed, the monarchs were subjected to a short training period. That training consisted in creating a positive association with an olfactory and visual stimulus. For instance, when the scientists presented the color orange, it was associated with a sweet reward, whereas the color blue was not. The same principle was applied for olfactory stimuli.

Surprising results

Now, time for the real challenge! Twenty-four hours after the training period, the monarchs were put to the test through a repetition of the exercise, but this time without a sweet reward. Result: 80 percent of the monarchs had the right answer!²A right answer was obtained when the monarch chose a smell or a color that during the training period had been associated with a sweet reward.

These results suggest that monarchs assimilate knowledge at a surprising speed. More astonishing still is the capacity of monarchs to retain that information over the long term. In fact, seven days after the training period, more than half the individuals still remembered what they’d learned!²

A highly useful memory

These experiments demonstrate that monarchs have a form of long-term memory. Even more, this would be the longest retention period for visual and olfactory information recorded among insects.²

For the monarch, olfactory memory and memory of colors would minimize the time and energy spent on looking for nectar-producing flowers during their fall migration.² That saving allows the butterfly to conserve more lipids, an energy reserve essential to its survival during the winter.

Speaking of memory, don’t forget to take part in the International Monarch Monitoring Blitz, being held from July 29 to August 7, 2022. Add your observations to those made by thousands of other participants in North America. It’s your chance to be part of the three-nation monarch conservation efforts!

References

1. Blackiston, Douglas J. et al. (2008), “Retention of Memory through Metamorphosis: Can a Moth Remember What It Learned As a Caterpillar?” PloS One, 3(3), doi:10.1371/journal.pone.0001736
2. Gegear, R.J. “Exploring the Role of Cognition in the Annual Fall Migration of the Monarch Butterfly (Danaus plexippus).” Insects 2021, 12, 760. https://doi.org/10.3390/insects12080760

Also read:

• What’s the monarch’s favorite milkweed?
• Monarchs and milkweeds, a complex relationship
• Monarchs know how to take care of themselves
• Monarchs don’t like heavy metal!