Category Archives: Security

Sphere of influence

How far do honey bees fly? An easy enough question, but one that is not straightforward to answer.

The flight range of the honeybee ...

The flight range of the honeybee …

Does the question mean any honey bee i.e. workers, drones or the queen? As individuals, or as a swarm?

Is the question how far can they fly? Or how far do they usually fly?

Why does any of this matter anyway?

Ladies first …

Workers

The first definitive experiments were done by John Eckert in the 1930’s. He located apiaries in the Wyoming badlands at increasing distances from natural or artificial forage 1. Essentially the bees were forced to fly over a moonscape of rocks, sand, sagebrush and cacti to reach an irrigated area with good forage. He then recorded weight gain or loss of the hives located at various distances from the forage.

Wyoming badlands

Wyoming badlands …

The original paper can be found online here (PDF). The experiments are thorough, explained well and make entertaining reading. They involved multiple colonies and were conducted in three successive years.

Surprisingly, Eckert showed that bees would forage up to 8.5 miles from the colony. This means they’d be making a round trip of at least 17 miles – and probably significantly more – to collect pollen and nectar.

However, although colonies situated within 2 miles of the nectar source gained weight, those situated more than 5 miles away lost weight during the experiments.

Gain or loss in hive weight ...

Gain or loss in hive weight …

Therefore, bees can forage over surprisingly long distances, but in doing so they use more resources than they gain.

John Eckert was the co-author (with Harry Laidlaw) of one of the classic books on queen rearing 2. His studies were probably the first thorough analysis of the abilities of worker bees to forage over long distances. Much more recently, Beekman and Ratnieks interpreted the waggle dance (PDF) of bees to calculate foraging distances to heather. In these studies, only 10% of the bees foraged ~6 miles from the hive, although over 50% travelled over 3.5 miles.

Queens

Queens don’t get to do a lot of flying. They go on one or two matings flights, perhaps preceded by shorter orientation flights, and they might swarm.

Heading for a DCA near you ...

Heading for a DCA near you …

I’ll deal with swarms separately. I’ll also assume that the orientation flights are no greater than those of workers (I don’t think there’s any data on queen orientation flight distance or duration) at no more than ~300 metres 3.

On mating flights the queen flies to a drone congregation area (DCA), mates with multiple drones and returns to the colony. DCA’s justify a complete post of their own, but are geographically-defined features, often used year after year.

There are a number of studies on queen mating range using genetically-distinguishable virgin queens and drones in isolated or semi-isolated locations. They ‘do what they say on the tin’, drone congregate there and wait for a virgin queen

In the 1930’s Klatt conducted studies using colonies on an isolated peninsula and observed successful mating at distances up to 6.3 miles

Studies in the 1950’s by Peer demonstrated that matings could occur between queens and drones originally separated by 10.1 miles 4. These studies showed an inverse relationship between distance and successful mating.

More recently, Jensen et al., produced data that was in agreement with this, with drone and queen colonies separated by 9.3 miles still successfully mating 5.

However, this more recent study also demonstrated that more than 50% of matings occurred within 1.5 miles and 90% occurring within 4.6 miles.

Just because they can, doesn’t mean they do 🙂

Drones … it takes 17 to tango …

Seventeen of course, because that’s one queen and an average of 16 drones 😉

There’s a problem with the queen mating flight distances listed above. Did the queen fly 9 miles and the drone fly just a short distance to the DCA?

Or vice versa?

10 miles ... you must be joking!

10 miles … you must be joking!

Or do they meet in the middle?

Do queens choose 6 to fly shorter distances because it minimises the risk of predation and because they are less muscle-bound and presumably less strong flyers than drones?

Alternatively, perhaps drones have evolved to visit local DCAs to maximise the time they have aloft without exhausting themselves flying miles first?

Or getting eaten.

It turns out that – at least in these long-distance liaisons – it’s the queen that probably flies further. Drones do prefer local DCAs 7 and most DCAs are located less than 3 miles from the ‘drone’ apiary 8.

Swarms

I’ve discussed the relocation of swarms recently. Perhaps surprisingly (at least in terms of forage competition), swarms prefer to relocate relatively near the originating hive. Metres rather than miles.

The sphere of influence

Effective foraging – in terms of honey production (or, for that matter, brood rearing) – occurs within 2-3 miles of the hive. This distance is also the furthest that drones usually fly to occupy DCAs for mating.

Queens can fly further, but it’s the law of diminishing returns. Literally. The vast majority of matings occur within 5 miles of the hive.

In fact, other than under exceptional circumstances, a radius of 5 miles from a colony probably represents its ‘sphere of influence’ … either things that can influence the colony, or that the colony can influence.

Why does this matter?

Worker flight distances are relevant if you want to know the nectar sources your bees are able to exploit, or the pollination services they can provide. In both cases, closer is better. It used to also be relevant in trying to track down the source of pesticide kills, though fortunately these are very much rarer these days.

Closer is better ...

Closer is better …

Workers not only fly to forage on plants and trees. They also fly to rob other colonies. I don’t think there are any studies on the distances over which robbing can occur, but I’ve followed bees the best part of a mile across fields from my apiary to find the source of the robbing 9.

All of these movements can also transport diseases about, either in the form of phoretic Varroa mites piggybacking and carrying a toxic viral payload, or as spores from the foulbroods.

Drone and queen flight distances are important if you’re interested in establishing isolated mating sites to maintain particular strains of bees. My friends in the Scottish Native Honey Bee Society have recently described their efforts to establish an isolated queen mating site in the Ochil Hills.

And I’m interested as I now have access to a site over 6 miles from the nearest honey bees in an area largely free of Varroa.

It’s not the Wyoming badlands, but it’s very remote 🙂


 

Google maps and apiary security

The increased interest in beekeeping over the last few years has meant there is considerable demand for bees, either for beginners or to replace stocks lost over the winter. The impatient and unscrupulous have resorted to bee rustling, either directly or indirectly. It is therefore sensible to take precautions to prevent the theft of your hives and nucs. This subject was covered extensively a couple of years ago in a post on Beekeeper UK which described branding, locks, ground anchors and other deterrents and is recommended reading. However, one aspect of security worth reinforcing is the impact of new digital technology – specifically smartphones and satellite imagery – which can be used to locate hives.

GPS-tagged image

GPS-tagged image

Smartphone cameras (and many new digital cameras) embed the GPS coordinates into their images. This information is contained within the exif (an abbreviation for exchangeable image file) data in the image, which also includes details of the camera, exposure etc. This can be readily viewed using online tools such as Jeffrey Friedl’s Exif (Image Metadata) Viewer. To illustrate this I’ve uploaded an image (right) taken when out cycling – so not compromising my own apiary security – with an iPhone a few years ago. If you point the Exif Viewer at the image you can extract all the embedded information, including both the GPS coordinates and a Google Maps view, as shown here. You can then use Google Streetview to see the, er, street view of the scene (if their little cars have visited).

Google Streetview

Google Streetview …

So what? I don’t share my images online …

OK, so much for the introduction to a potential problem, why should it be of interest or relevance if you don’t post GPS-tagged images on your personal blog, Facebook page, Instagram account, internet discussion forums, Flikr, 500px etc.?

… three rows of hive stands, cars provide scale

Baton Rouge labs

The real problem isn’t the GPS-tagged images at all (I’ll describe an easy solution to this later in this post), rather it’s the resolution of the online satellite images provided by Google, Bing and others. These are good enough now to locate apiaries relatively easily and to see individual hives in certain circumstances. They’re also going to get a lot better soon. Rather than compromise an amateur beekeeper, or publicise an otherwise hidden apiary, here is an image containing  three rows of hives (on rail stands) at the ARS Honeybee breeding, genetics and research labs in Baton Rouge, Louisiana, USA … I think it’s fair to say it’s no secret that they’ll have apiaries on site 😉  And below is the view from ground level, taken in a different season with the trees in full leaf. The cars in the satellite image provide a sense of scale.

Baton Rouge apiary

Baton Rouge apiary …

Google Maps (and Bing and others) satellite imagery are of similar resolution for the USA and the UK. The satellite image above is not even at maximum size … when it is you can pretty easily count individual hives. This was brought home forcefully when processing a smartphone image (with embedded GPS coordinates) in Adobe Lightroom. The Map module showed a neat row of hives in the corner of a field. Google updates the images they use reasonably frequently, so even if your colonies are not visible now they might be soon after the next satellite passes over.

Security by obscurity

How can you prevent your apiary from being detected? Of the local apiaries I’m aware of I couldn’t detect those that:

  • were located under light tree cover. This would seem to be both practical and relatively easy to achieve. As long as they are not in deep shade it can also make for a much more pleasant inspection experience on a sweltering hot day, and the trees or hedges can provide shelter from strong winds.
  • contained only individual hives. Whilst absence of evidence isn’t evidence of absence it is certainly easier to detect neat rows of hives along field boundaries or angled across the corner of a meadow.
There you are!

There you are!

The most obvious hives were those in which the roof contrasted with the ground. This was particularly marked with bright, shiny, metal roofs glinting in the sun. Older, tattier, hives or those with roofs covered in roofing felt were more difficult to find. Perhaps it might be worth applying camouflage paint to new hive roofs. Irregularly placed hives in dark or muted colours that didn’t contrast with the ground were generally tricky to see.

None of these precautions are foolproof. None of them negate the need to keep your colonies in secure, private locations, preferably behind locked gates. However, they might be useful in preventing unwanted attention.

But what about my online images?

Some image hosting sites automagically strip location-sensitive information from uploaded images. Others do not. On the principle that it’s better to be safe than sorry it’s worth always ensuring the uploaded images do not contain this information. Phones usually have an option to exclude GPS data from images. Alternatively (and to avoid omitting the location information from all the images you want to keep it in) it’s easy to strip unwanted exif data, including all the GPS data, using software. If you’re an Adobe Lightroom user this is an option under the ‘export’ menu. Alternatively, ImageOptim is an excellent (and free) Mac application that compresses images, strips out unnecessary metadata including all the location information and removes unnecessary colour profiles. This typically reduces the file size by 10-20% and works with a range of graphics format images. The image per se is unaltered. It runs as a Service on the Mac, which makes it even easier to use.

Not GPS-tagged

Not GPS-tagged …

The GPS-tagged image of the bike on the fence at the top of the page is 242 kB. After using ImageOptim this is reduced to 213 kB in size. More importantly, as far as security is concerned, Jeffrey’s Exif Viewer now shows no geographical information. It even hides the embarrassing fact that my smartphone is over four years old 😉

There are also ways of removing exif data from your images if you use Windows. I’ve not used these and cannot comment on how well they work.