Honey bees preferentially consume freshly-stored pollen

Authors: Carroll, Mark; Goodall, Craig; Brown, Nicholas; DOWNS, ALEXANDRA - University Of Arizona; Sheehan, Timothy; Anderson, Kirk

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2017
Publication Date: 4/21/2017
Citation: Carroll, M.J., Goodall, C.R., Brown, N.J., Downs, A.M., Sheehan, T.H., Anderson, K.E. 2017. Honey bees preferentially consume freshly-stored pollen. PLoS One. 12(4):e0175933. doi: 10.1371/journal.pone.0175933.

Interpretive Summary: Honey bees collect and store pollen in cells in a preserved form known as stored pollen, or beebread. Bees add nectar and honey to collected pollen to form stored pollen. Bees eat stored pollen from a wide selection of pollen cells that have been stored for different lengths of time. We examined the feeding preferences of honey bees for different-aged stored pollens. We monitored the addition and removal of individual pollen cells from 18 brood frames in 6 colonies over 8 days time. Despite a greater number of older pollen cells on the frames, bees preferred to consume freshly-stored pollen cells instead of older pollen cells. Newer pollen cells were eaten more often than expected, while older pollen cells were eaten less often than predicted. Similar preferences were observed in choice tests where caged bees were given a choice between two equal-sized blocks of different-aged pollen cells. Bees consumed 1 day-old pollen three times as much as 10 day-old pollen and two times as much as 5 day-old pollen. These feeding preferences for freshly-stored pollen occurred despite a lack of clear advantages to bee development. Young adult bees reared for a week on 1 day-old, 5 day-old, or 10 day-old pollen cells did not differ in body mass or feeding gland nutrient amounts. Our results do not support a commonly held idea that stored pollen improves in taste or nutritional value with time. Rather, pollen cells that are not eaten in the first few days build up as extra pollen cells on colony frames. Bees’ preferences for fresh stored pollen may be due to leftover odors produced by microbes or the pollen grains before preservation. This study may be used to improve the taste of supplemental feeds to bees.

Technical Abstract: Honey bees collect and store pollen in cells in a preserved form known as stored pollen, or beebread. To preserve pollen, bees add nectar and honey to collected pollen to form stored pollen. Bees eat stored pollen from a wide selection of pollen cells that have been stored for different lengths of time. We examined the feeding preferences of honey bees for different-aged stored pollens. We monitored the addition and removal of individual pollen cells from 18 brood frames in 6 colonies over 8 days time. Despite a greater abundance of older pollen cells on the frames, bees preferred to consume fresh pollen cells rather than older pollen cells. Two to five day-old pollen cells were consumed more often than expected by random feeding alone, while 8 day-old pollen cells were eaten less often than predicted. Similar preferences were observed in caged bee experiments where bees were given a choice between two equal-sized blocks of different-aged pollen comb. Bees consumed 1 day-old pollen three times as often as 10 day-old pollen and two times as often as 5 day-old pollen. These feeding preferences for fresh stored pollen were observed despite a lack of clear advantages in bee growth and development. Young adult bees reared for 7 days on 1 day-old, 5 day-old, or 10 day-old pollen cells showed no differences in body mass or hypopharyngeal gland protein content, suggesting that these pollens have similar dietary value to bees. Our results do not support a commonly held hypothesis that stored pollen improves in palatability or nutritional value with time. Rather, pollen cells that are not eaten in the first few days accumulate as excess pollen stores in the colony. Bees’ preferences for fresh stored pollen may be due to leftover odors produced by microbes or the pollen grains before preservation. These feeding preferences may be used to improve the acceptability of supplemental feeds to bees.