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Bumble bees -

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Bumble bees

Offspring care takes a lot of time for bees. Bumble bee larvae are immobile for just over three
weeks and need to be cleaned, fed, and protected. Bumble bees differ from honey bees in their life
cycle. A honey bee can last for 20 years or more. Bumble bee colonies last for only one season. The
bumble bee nest, based on the queen, can be made up of a few hundred individuals. Anna Dornhaus
describes bumble bee behaviour and society.

Transcript

Robyn Williams: Have you been following Bush Telegraph on this network, tracking the fate of bees
and honey, both here, in Australia and in New Zealand?

[excerpt from Bush Telegraph]

We're in the University of Arizona. I've joined Anna Dornhaus, with a number of colonies, charming
ones, tiny ants and lots and lots of colonies of bumblebees. Anna Dornhaus, the first thing that
strikes me, they look a bit like works of art, not the normal kind of honeycomb but like the sort
of things that you see in coral reefs, these cup-shaped places where they crawl over. But the thing
that strikes me most of all about the charm of this, you've managed to get tiny numbers on their
backs so you can tell one bumblebee from another. How on earth did you manage that?

Anna Dornhaus: A lot of people ask me that. It's actually not as hard as it looks. All we do is
cage them in a little plastic cage and then we use a piece of foam to press them against the mesh
and then they're immobilised even though they're awake, but they can't move. And then through the
mesh we actually glue these little plastic tags onto their backs.

Robyn Williams: Why do you need to know one from the other?

Anna Dornhaus: Because we're interested in what goes on in their society, we're interested in how
they interact with each other, and in particular right now we're interested in whether they
specialise on particular jobs and why they do that. So in order to recognise that an individual
specialises on a job, does the same job day in, day out, we have to recognise that individual from
other individuals.

Robyn Williams: They're not in a hive, they're in fact boxes with a kind of bedding, the
construction is in the middle and they're crawling over them in a fairly calm way, although when I
first came in, it made the new colony go kind of berserk, they're running around all over the
place, but they're kind of serene and relaxed. What are they doing now?

Anna Dornhaus: It's an interesting question, and the fact that you say they're so serene is
actually something that's been puzzling social insect researchers for decades. The fact is, most of
them aren't doing anything that we can recognise as work. So there is actually a lot of either
loafing around or doing secretive tasks that we haven't identified. A lot of them are in fact busy
with brood care, the care for your own offspring. In bees it's an immense amount of work. Their
development time from egg to adult is almost as long as the adult lifespan. So for animals that's
an incredibly long time where the adults have to take care of their babies.

Robyn Williams: Is that a few weeks?

Anna Dornhaus: Yes, a few weeks, so about 3.5 weeks for bumblebees, it's depends a little bit on
the temperature. But in this whole time the babies, the larvae we call them, are essentially
immobile and like human babies they have to be cleaned, they have to be fed, they have to be kept
warm but not too warm, they have to be protected from attackers and they also have to be protected
from parasites. And so each offspring is going to be constantly patrolled by adult workers, checked
out and cleaned and so on.

Robyn Williams: The whole setup looks totally different from honeybees. In what way are the
bumblebees' lives different from honeybees?

Anna Dornhaus: They are different in many ways but I guess the most striking one is their life
cycle. Honeybees live in colonies of at least a few thousand individuals, up to 50,000, 60,000
individuals, and the colonies are perennial which means that a honeybee colony can last for 10 or
20 years or longer really if they replace the queen. So honeybee colonies last for a long time.
Bumblebee colonies, by contrast, only ever last for one season. So a bumblebee nest originates by a
queen who founds the nest in early spring, initially the queen is all by herself, she's raising her
own offspring all by herself, and once she has raised the first workers those workers then help her
and the nest slowly grows to a few hundred individuals at most. So a bumblebee colony never grows
as large as a honeybee colony and it never lasts as long.

Robyn Williams: And there is the queen, is it, that very large one at the top?

Anna Dornhaus: Yes, indeed, that is the queen. The queen is larger than the other individuals.
She's female but the other individuals are all also females, however the other individuals are
workers, they're smaller then the queen and they also don't have ovaries that are quite as
functional. So essentially they're almost asexual, they don't usually reproduce, the queen is the
only one reproducing. And the queen is in fact the mother of everybody in the colony. So all of
these so-called workers are really her daughters helping her reproduce more.

Robyn Williams: And they all do their jobs? There are no rebels? You don't have two or three of
them who decide that they're going to do their own thing and be individualistic?

Anna Dornhaus: Actually, you know what, that's an interesting topic. In honeybees that practically
never happens, there are no rebels almost ever. In bumblebees there is very regularly a sort of
mutiny against the queen but it only happens very late in the season. So towards the end of the
year in late summer, some of the workers will get it in their heads that they're actually almost as
big as the queen and that they would be able to produce eggs as well. And so they start developing
their ovaries, they start laying eggs. The queen doesn't like this and very often she will beat up
these workers quite physically. She will also go and try to eat their eggs if they have started
laying eggs. And interestingly the workers don't like each other laying eggs either, so the workers
will actually eat each other's eggs as well as beating each other up.

And sometimes the result of all this aggression that happens is actually that the queen gets
killed, although she has an advantage because she's bigger, but sometimes she gets killed. If the
queen dies, for this reason or any other reason, several of the bees in the nest will start laying
eggs. Workers, even though they're females, are not fully developed, so they don't actually have
the equipment to mate with a male, all the eggs that they lay are unfertilised. But in bees and
ants these unfertilised eggs can develop and they develop into males. So these workers are able to
produce males, even if the queen dies.

Robyn Williams: Even though I can't see males there, should they need one somewhere towards the end
of the season or whenever, they just make them.

Anna Dornhaus: In a sense yes, although the males that they produce, in a sense, are not for their
own use because of course they would be their brothers, or in the sense of the queen it would be
her son, and they never inbreed, so they will not mate with their own sons or brothers. The males
will leave the nest and they will search for other bumblebee nests in order to find other bumblebee
queens that they can mate with.

Robyn Williams: When they go out on their flight?

Anna Dornhaus: Yes.

Robyn Williams: Do you know there's a scientist in Australia, actually an Indian, called Srinivasan
who has actually worked out that they can navigate, learn how to go in different directions during
their short lifetime, these bees. I don't know about bumblebees but certainly honeybees.

Anna Dornhaus: Yes, indeed. I know Srini very well, I actually knew him when I did my PhD back in
Germany, and he's not the only one, there is a whole series of studies, starting from Karl von
Frisch who got the Nobel Prize for behavioural biology who found out that honeybees can learn
different routes...

Robyn Williams: Through dancing.

Anna Dornhaus: Yes, in fact the dancing is one of the less flexible parts of the thing. So
honeybees can tell each other the locations of food sources through dancing. Interestingly
bumblebees will also dance but they only tell each other the smell of the food source, they don't
tell each other where it is. So there is fascinating behaviours that they use to communicate or
exchange information, absolutely. Actually a group in Switzerland just found out that honeybees
also have cognitive maps, so they can find novel routes that they haven't practiced, in a sense.

Robyn Williams: Anna Dornhaus. And by the way, I also asked her about the colony collapse that
everyone's been talking about, and she tells me about the huge plantations of almonds, that's nut
trees grown in California, which need millions and millions of bees to be trucked in to serve the
flowers, trucked in in such numbers that diseases can explode. Ann Dornhaus is a professor at the
University of Arizona in Tucson.