One of the most disappointing things that can happen to a beekeeper in a developing country is to have a colony abscond. It is not only disappointing but may seriously affect the viability of the beekeeping business so some understanding of the factors that underpin absconding are important to beekeepers. Absconding may be defined as the complete abandonment of the nest by the whole colony. It differs from swarming in that the nest does not divide into two or more parts but the whole colony moves and presumably seeks and finds a new nest site elsewhere. Beekeepers in many places benefit from this planned absconding (or migration) to fill their empty bee hives.
The tendency to abscond is mainly determined by climate and the effects of climatic change on flowering and nectar flow. Honey bees have two possible strategies for surviving periods of dearth;
1) by storing sufficient quantities of honey to enable them to survive during the dearth period or
2) by moving to another place where there may be greater nectar flow available.
For temperate bees the absconding strategy is almost never used as it is likely to be fatal to the colony - an absconded colony would be most unlikely to collect enough stores for it to survive the lengthy dearth periods it will encounter. Tropical bees, African and Africanised bees and tropical species of Apis cerana however, may utilise either the hoarding or the absconding strategy to survive dearth periods and may show high levels of absconding.
There are two types of absconding; planned and unplanned absconding. Winston (1987) calls this disturbance-induced absconding and resource-induced absconding. These definitions speak for themselves; disturbance-induced (or unplanned) absconding can be induced by predation, or invasion of the colony by undesirable pests, such as hive beetles, ants or wax moths. Poor physical conditions such as entry of water into the hive, excessively high temperatures due to lack of shade or shortage of water, the proximity of bush fires or excessive disturbance can also encourage colonies to abscond.
Resource-induced (or planned) absconding appears to occur due to scarcity of nectar, pollen or water and occurs primarily during the dearth periods found in tropical conditions. Resource-induced absconding tends to be seasonal and differs from disturbance-induced absconding in that colonies start preparing to abscond up to one month in advance of actually leaving. Firstly, the queen will reduce her egg laying rate so that very few larvae will be reared during this period. Those few eggs that are laid will be eaten by the workers. Most of the stored pollen and honey is also consumed by the bees. As soon as the last young brood has emerged the colony will abscond. By doing this they ensure they have a good number of relatively young bees and the consumption of pollen means their fat bodies will be full of stored protein, ready to start rearing new workers in the new place.
Absconding rates are on average 15-30% annually and can be as high as 100% in some seasons. These are important factors to take into account. In essence it means that it is likely that up to 1/3rd of the bees in any one place can be lost. The beekeeper needs to take this into account when calculating the number of hives that need to be kept if beekeeping is being undertaken as a business rather than as opportunistic honey collecting. It is especially important to consider if a high cost system of beehives had been taken on especially if this has started with microfinance borrowing.
Since not all colonies abscond these factors are not the complete answer to the questions posed by absconding. One feature of absconding is the condition of the colony as well as the availability of resources. Winston (1987) notes that colonies that abscond are those that have swarmed within 6 weeks of the dearth period which would leave them with fewer workers, more older workers and a lower brood viability than colonies that have not swarmed. He also notes that absconding colonies can travel much greater distances that normal swarms - up to 160km before starting a new nest site. They may travel through areas of poor resources, sending out scout bees to search for suitable forage until they find an area of greater resources to settle in.
Where it is possible, feeding bees can help to limit the level of absconding but it would take good observation and assessment of the colonies that are likely to swarm to make this worthwhile. Aggressive predation and resource limitation in the tropics is likely to lead to higher death rates for topical colonies. However, short intervals between swarming and high number of swarms are likely to offset higher death rates among tropical bees.
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