Finding dead bees can cause concern, but
if you have found dead bees in your yard, garden, beneath a tree or
simply on the pavement, there are various possible
explanations, depending on the species and circumstances.
Sometimes, the causes are natural rather than sinister. All creatures live then die, either due to
age, disease, weather, natural predators and so on.
Pesticides are certainly a cause for concern - see the links in the navigation bar right for further information - there is much information on this website, especially with regard to neonicotinoids.
Most individual bees have very short life spans – as little as a few short weeks. The only exceptions within a colony are the queens.
You can read more on my page: How Long Do Bees Live?
In my experience, the majority of people tend to report specifically seeing dead bumble bees, that is, with the exception of beekeepers – we’ll get to that in a moment
If you have found dead bees – usually up to around ten, all within a confined area, and you believe they are bumble bees, then most commonly this is part of the normal bumble bee colony lifecycle. Bees will clear out their nests to preserve hygiene, and this includes removing dead bees.
The possible reasons for the death of these bees in the first place could be natural causes such as age, disease, or attack from a predator, resulting in casualties. Usually, there will be a nest nearby – although perhaps you haven’t seen it.
bumble bee nests can feature in a variety of places: high above ground
(even in bird boxes), but also underground in abandoned rodent holes, or in
clumps of grass.
Please note too, that at the end of the season, in the vast majority of cases,
only the new bumble bee queens will live and establish new colonies the
following year, whilst the rest of the bumble bee colony will sadly not survive.
A few exceptions are being reported (i.e. with bumble bee colonies surviving the winter), and there are differences in some warmer climates.
Last year, my sister found dead bees by her pond. When I asked her for further information, it turned out they were bumble bees. They had made a nest by the water’s edge, and the dead bees were found around the entrance. More than likely, the reasons were part of the normal lifecycle and trials of an average bumble bee colony.
If you have found many dead bees around the base of a tree, check whether the tree is a lime.
To quote an excerpt from 'A Sting In The Tale' by Professor Dave Goulson (also author of Bumblebee Behaviour And Ecology):
So it seems some lime trees are toxic for bees – with some species believed to be more harmful for bumblebees than honey bees.
Some of these lime trees are irresistible to the bees, but sadly they are fatal for them.
I’m concerned about a trend to import ornamental species of lime for
gardens without any consideration at all for the effects on local
wildlife. Personally, I would like to
see this behaviour regulated and banned where toxic effects are noted.
Alternatively, has the tree been sprayed with pesticide? If so, it could be a case of acute poisoning (rather than chronic poisoning), and you may see other dead insects aound the same area.
If you suspect poisoning, I recommend you collect evidence – dead specimens, photographs, and any information you can about the use of pesticides at the location, then report it to your local authority, or health and safety organisation.
Some countries have
specific places where wildlife poisonings are meant to be reported –
with a relevant government body.
Personally, I would try to keep back some of the evidence – copies of
photos and a number of dead specimens, because the effectiveness of
schemes for reporting poisonings can be
variable. Neonicotinoid pesticides are a particular cause for concern.
Have you found a dead bee (a single specimen), perhaps on the ground or even on a plant? Again, the reasons could be perfectly natural, for example, because of the age of the bee, due predator attack, internal parasites or disease. Some bees can be mistaken for dead, when in fact they are resting. If you have found a bee alive, but in need of a little TLC, go to this page.
If you find a whole
colony of dead bumble bees – i.e. in the nest, then it is likely that this is
due to the invasion of a predator or parasite, and there may be visible signs
of this, such as silky webbing (wax moth) or the parasites and their larvae may
themselves be visible.
If you come across an infested nest, sadly, there is generally little you can do to help the bees at this stage.
Honey bee colonies are meant to survive the winter (see Where Do Bees Go In Winter).
However, finding a few dead honey bees is perfectly normal. Again, dead bees are automatically removed from the nest or hive. During the winter, there will usually be more casualties, and this is known as ‘winter mortality’.
Sometimes, honey bee colonies will succumb to inclement weather conditions during 'cleansing flights' - they leave the hive for a short while, but unfortunately they can get caught out if the weather suddenly turns against them. This was the case in the photograph at the top of the page, when in fact, many bees were found dead as a result of a snow storm You can read about it here.
This is significantly different from the exceptional losses reported in recent years, with beekeepers losing around 30% of colonies or more due to colony collapse disorder (although this ‘condition’ is a term used to describe a number of phenomena, with variations in definitions and symptoms reported).
a system for recording collapses, and it’s important to record these
However, it is my personal view that the impact of pesticides should also be considered, since they may significantly weaken the colony and make them more vulnerable to diseases.
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