Do Honeybees Sleep?

All the bees at Brookfield Farm, in Maple Falls, Washington are tucked up in their clusters in their hives.  Some are probably asleep, some awake.  It depends on their age and their job.  But none are getting a good 40 winks, unless a “wink” is a second.  Bees sleep in small naps, but some sleep more regularly than others.  What follows is what I have gleaned from my readings.

The most complete study I found on-line is at http://jeb.biologists.org/cgi/content/full/211/18/3028.  This study by Barrett A. Klein, Kathryn M. Olzsowy, Arno Klein, Katharine M. Saunders and Thomas D. Seeley was first published on-line in September 2008, in the Journal of Experimental Biology.  This quite fascinating and elegant study is called: Caste-Dependent Sleep of Worker Honey Bees.

WHAT IS SLEEP? (As defined by the above study)

Sleeping bees are immobile bees whose bodies and legs hang in the direction of gravity.

The researchers then decided on three different forms of sleep: immobile; immobile with twitching antennae; and immobile with immobile antennae.

Sleep can occur in many places: in a cell, hanging off comb, on the hive wall, or even on the floor.

Where and when bees sleep is determined by their age and their jobs.

THE YOUNG ARE “WHENEVER”, THE OLD LIKE A LITTLE REGULARITY

Young bees tend to sleep inside cells in the center of the hive.  They don’t have regular sleep cycles, but catch a quick nap (we’re talking 30 seconds here) whenever they can.  These young bees tend to wake up for a few hours, then go back to sleep.

Older bees tend to sleep on the outer edges of the hive.  They sleep in longer increments and at more regular intervals, usually at night.

How sleep patterns changes as the bees age:

Cleaners (up to 3 days old) sleep in the shortest “bursts”, but they usually sleep in the cells

Nurses (4-12 days old) sleep in longer time spans, and fewer sleep in cells

Storers’ (13-20 days old) naps are even longer, only a few sleep in cells

Foragers sleep for the longest durations mostly at night, but seldom in cells

LOCATION, LOCATION, LOCATION

The locations make sense:  Young bees work as cell cleaners and nurse bees.  They are walking and working in the heart of the hive.  It is speculated that catching a quick nap in a cell protects them from being bumped and nudged by the other bees working around them, plus it is warmer in there.

Older bees are packing stores and working as foragers.  The foragers tend to sleep outside the cluster.  Again, this is speculation but the location would provide for a bit a peace from the hustle and bustle of the hive.  In fact, if they do catch a nap in the day, they may crawl into a cell, where it would be calm and quiet.  The tendency of foragers to sleep on the outside of the cluster would also keep any diseases or parasites that they might have picked up, out of the brood area of the hive.

HOW SLEEP CHANGES WITH AGE

The difference in time slept makes sense to me: When creatures are young they simply have more energy. A quick nap here is just fine before they bustle off to their jobs.  Jobs which  involve dealing with the eggs and larvae, whose demands have no fixed schedule.

Foragers are under a lot of stress and expending a lot of energy on their collection rounds.  They, as many older creatures do, need to get some sleep on a regular basis. It is not surprising that foragers and food storers tend to sleep at night.  Their work is daylight dependent.  Even if their job is to put the food away, there is no food coming in at night.  At least 50% more foragers catch their sleep in the night than in the day.

WHAT HAPPENS WHEN BEES DON’T SLEEP

Dr. Klein has just completed a study on this as well.  He got bees into little metal harnesses (the thought boggles the mind), and then woke them up using magnetics when they tried to sleep.  The result was a decline in their communication skills: they couldn’t dance as well. Not a loss in the human world, but dancing is how bees tell each other where the honey, pollen, or new hive locations can be found. The drop in communication skills by tired bees is not terribly surprising, but, to me, it is an incredible study.  It can be found, in short form at: http://www.utexas.edu/news/2010/12/13/biology_bees/

You can watch tired bees doing a failed dance at: http://www.youtube.com/watch?v=rOPz7C88LgU

STUDYING SLEEP

Caste-Dependent Sleep of Worker Honey Bees: Barrett A. Klein, Kathryn M. Olzsowy, Arno Klein, Katharine M. Saunders and Thomas D. Seeley  http://jeb.biologists.org/cgi/content/full/211/18/3028

Sleepless Honey Bees Miscommunicate, Too, Research at The University of Texas at Austin Shows: Dr. Barrett Klein and Dr. Ulrich Mueller.

The Buzz About Bees a book by Jurgen Tautz (there’s an umlaut, I just can’t make one here)

Differences in the sleep architecture of forager and young honeybees (Apis mellifera) Journal of Experimental Biology (2008) by Ada D. Eban-Rothschild and Guy Bloch

Do you have any insights about how and when bees sleep?  Do share, learning is a life-long experience.

That’s the news this week from Brookfield Farm Bees and Honey in Maple Falls, Washington.