Chewing the Fat

What does it take to get through winter? Bay of Plenty beekeeper 'Aimz' checks on fat stores and varroa sores as the days get shorter.

Surviving winter comes with its own challenges.

In my experience, a year beekeeping has revealed the strongest, fittest version of myself to date. But sometime, just recently, the world has turned cold and dark, and I have neglected to lay on my winter fat stores. Be that as it may, I believe my survival rate would still be pretty good.

What about the bees?  

Fat bodies are crucial for the longevity of overwintering bees. Not a fat body as such, but specialised cells in the body, an organ that has a dual-purpose function, acting both like a liver, by filtering toxins, and a protein storehouse, converting bee bread into a useable fuel.

Fat bodies are situated along the length of a bee’s abdomen and change in size throughout its life. Once emerged from its cell, a young bee is fed by nurse bees while its fat bodies are developing. After a few days the young bee, now physiologically mature, begins its own duties as a nurse bee, consuming large amounts of protein to be able to feed other members of the colony.

Having ‘fat’ stores means not only a greater chance of winter survival for the individual honeybee, but stimulates colony-wide benefits.

Now things are about to get really interesting, in the name of vitellogenin.

Vitellogenin is a jelly-like substance, described as an egg yolk protein precursor. Bees consume protein, in the form of pollen (bee bread), which is converted into vitellogenin and stored in the bee’s fat body. These stores are transported to the hypopharyngeal and mandibular glands, where it is used to create brood food and synthesize royal jelly.

Effectively, and collectively, the fat bodies of bees can be viewed as a communal food pantry, and the vitellogenin they store holds a vital key to the health of the colony.

As well as conveying immunity and regulating hormones and pheromones, vitellogenin levels can determine the longevity of bees, with large healthy fat bodies allowing bees to live longer. Bees are unique in that they can speed up or slow down aging, called plasticity in ageing, to regulate colony population in response to growth or contraction. When a bee’s vitellogenin levels are depleted, the fat body is used up and the bee dies.

Ensuring a honey bee colony has adequate pollen through the autumn months is essential to generating enough ‘bee bread’ to feed the brood which are destined to become long-lived over-wintered bees.

And winter bees? They are physiologically different to that of summer bees. Winter bees have the ability to do any task at any time and are not bound to ageing along a timeline of duties, as other bees are.

A determining factor of a winter bee is the lack of brood rearing pheromone. An overwintering bee cannot be raising brood, or its longevity is compromised. It needs a large healthy fat body to outlast the winter and allow it to forage for and nurse the new season’s brood.

When the fat bodies are damaged, namely through predation by varroa mites, the invisible damage can be devastating. Individual bees may lose the ability to thermoregulate and are more likely to succumb to low levels of pesticides. When a developing bee is parasitised by varroa within the cell, its growth is stunted, permanently. Not able to efficiently nurse other bees, these damaged bees age prematurely, as they mature through the stages of development faster. Colonies suffer in that it takes a great number more bees to act as nurse bees and feed the colony, leaving less to forage.

‘Fogging’ bees in the fog. Aimz undertakes some late-season varroa control using oxalic acid sublimation so help get them through to spring in the best possible shape.

The effect on winter bees is that without adequate stores of vitellogenin, those stunted bees will never become a long-lived bee, expiring halfway through winter. Therefore the entire longevity of the colony is imperilled by dwindling numbers.

Protecting our winter bees starts with critical timing with mite control. Varroa load wants to be at low levels before the bees start winding things down. The mites this year have been an eye opener for me, and a real sharp learning curve.

The other major contributor is of course encouraging large, healthy fat-bodies by ensuring bees have adequate protein supplies, especially in localities that suffer from a pollen dearth.

Phew, although only summarizing the tip of the iceberg, I just about lost myself in such an absorbing topic. Winter is a time for reflection and introspection, research and setting goals.

As I continue my journey into the finer workings of the hive, this phrase comes to mind; ‘when we know better, we do better’ – which is exactly the path I intend to take.

For now, I’ll keep reading. Yours, in the pursuit of knowledge and good intentions,

Aimz

P.S As you can tell I have been doing some research, at the school of YouTube: Ask a Washington Beekeeper: Fat Bodies and Bee Health (Nov 2023).

Aimz is a second-generation commercial beekeeper in the Bay of Plenty who took up the hive tool full time at the end of the 2024 honey season. Formerly a stay-at-home mum to four kids, she has now found her footing in the family business.