Honeybees 'read maps' to find home
Honeybees use mental maps to find their way home in a similar way to birds and mammals, researchers say.
Bees are known to use the sun in order to navigate, but scientists have debated the other methods they use.
A team of researchers "confused" a group of bees so they misinterpreted the position of the sun.
They found these bees returned to the hive with a similar speed and accuracy of non-disorientated ones, suggesting the additional use of "mental maps".
The results are published in the journal PNAS.
Mammals continuously build "cognitive maps" in their brains of familiar places, helping them recognise landmarks and judge directions and distances.
"The argument is usually that the very small brain in insects will not be able to perform such a demanding task," said Prof Randolf Menzel from the Freie Universitaet Berlin, Germany - part of the international team of researchers.
Bees' brains do not have the same structures as mammals for making these mental maps. But the study has revealed new evidence that honeybees recognise landmarks such as hedgerows and other, smaller features, "very much... as we experience or draw a map", explained Prof Menzel.
It has previously been thought bees rely mainly on the position of the sun as a compass in order to know where they are.
Honeybees are found in nearly every part of the world. In the wild, forager honeybees may visit about 2,000 flowers for pollen and nectar each day. It is thought they exchange information with others in the hive about the locations of flowers in relation to the sun, using movements known as a "waggle dance".
Prof Menzel and colleagues from Germany, New Zealand and the US wanted to test how honeybees (Apis mellifera carnica) found their way home when they released the insects in a large open field 400m (1,312ft) away from their hives.
To see if they relied on the sun to navigate, the team disorientated the bees by putting them under general anaesthetic for six hours to "shift" their biological clock. This would cause them to "misinterpret" the position of the sun and potentially become lost on their journey home.
Instead, the insects arrived at their hives with the same speed and accuracy as the bees that had not been "clock shifted", proving honeybees must use their remembered internal maps, as well as the sun, to find their way.
"We proved the existence of a cognitive map in honeybee navigation," said Prof Menzel, adding: "They must retrieve the information about their own location, and the location of the goal, only from the geometric relation of landmarks which they have learned before."
The team's discovery was made using new technology in bee navigation: a "harmonic radar".
The radar can track the flight of a single bee for up to 1km (0.6 miles) using transponders attached to the insect's thorax. This allowed the experts to observe the honeybees' natural navigation.