Posted in Science & Nature

Honeybee Dance

How do honeybees share the location of a food source, such as a flower, to other bees of their colony? An Austrian biologist named Karl Von Frisch devised an experiment to learn how the honeybees communicated with each other. He set up two different food sources and tagged every bee that came to pot A green and bees that came to pot B red. He then studied the behaviour of these bees back at the hive. What he discovered was fascinating.

For millennia, beekeepers have noticed that some honeybees have a tendency of moving in a peculiar yet methodical way once they returned to their hive after foraging for flowers. The bees would move in a straight line while waggling their bottom (moving side-to-side), then walk in a semicircle back to where they started. They would then waggle in the same direction, then move in a semicircle on the opposite side, completing a figure-eight path. This is called a waggle dance.

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Frisch noticed that bees with green spots and the bees with red spots both did the waggle dance once they returned to the hive, but in different directions. All bees with green spots danced so that the straight line pointed a certain direction, while the bees with red spots danced the same dance except pointing another direction. Amazingly, the angle between these two directions was exactly the same as the angle separating pot A and B (with the hive as a point of origin). Frisch deduced that the waggle dance was the language of honeybees.

Through further experimentation, Frisch was able to tease out the details of this “language”.

  • Honeybees’ eyes can see ultraviolet and polarised light, which allows them to see where the sun is in the sky at all times. This is because sunlight polarises so that it points towards the sun and honeybees can see this direction. Therefore, the bee’s eyes act as a solar compass that tracks the exact location of the sun in real-time.
  • Bees have a finely-tuned internal clock that allows them to predict exactly where the sun should be depending on time, season and latitude, as the sun moves through the sky.
  • Another point of reference that is used in the bees’ language is gravity. Gravity is a constant that does not change, meaning all bees know which direction is “up” and which is “down”. This also means they can use a vertical, perpendicular line as a standard zero-point.

By pairing the two global constants, gravity and the location of the sun, the bees can accurately signal to other bees the direction they should fly in to find the food source. If a bee does a waggle dance that points 60° right from the vertical “up” direction (as defined by gravity), it signals that the bees should fly 60° right from the direction of the sun. If the angle is 0°, the bees should fly directly towards the sun, and if the angle is 180°, the bees should fly directly away from the sun. The bees use their internal clock to calibrate the direction depending on the time of the day.

The straight line “waggle” part of the dance gives the information of distance. The longer the duration of the straight line, the further away the flower is. As a general rule of thumb, the duration of the straight line increases by 1 second for every 1 kilometre. When the food is within about 60m of the hive, the 8-shape waggle dance turns into an O-shape round dance. The bee deduces the distance by the energy required to fly to the location.

By encoding the two variables “direction” and “distance”, a bee can effectively use the waggle dance to accurately pinpoint the location of a food source. It is amazing to see that animals that we consider “primitive” such as bees have such an intricate method of communication.

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(Image source: http://aireona93.deviantart.com/art/YAY-Waggle-Dance-146361214?q=boost%3Apopular%20waggle%20dance&qo=1)

Posted in Science & Nature

Badass Weapons Of Nature: Long-tailed Weasel

Long-tailed weasels are ferocious predators found in North America that likes to stalk its prey and pounce it with lightning speed. With small prey such as mice, the weasel will wrap its long body around the prey and then crush the head with a strong bite. As the weasel is very slender and sleek, it can easily dig into burrows to hunt hiding animals by crushing its skull, or to add variety, ripping out the windpipe.

Although it usually preys on small rodents, the long-tailed weasel is also known to fearlessly attack much larger animals such as birds and rabbits. As wild rabbits tend to be bulkier (sometimes even ten times larger) than the weasel, it cannot use its characteristic hunting style. To overcome this difficulty, these weasels have developed a strange behaviour that zoologists have labelled the Weasel War Dance. The War Dance (NB: two videos on what it looks like) is a chaotic set of movements where the weasel runs left and right frantically, jumping and flipping upside-down and almost appearing insane. This type of behaviour is observed in other species of weasels and ferrets when they are excited, but few use it as a hunting tool.

It has been observed that when the long-tailed weasel performs a War Dance in front of a rabbit, the rabbit becomes dazed and enters a trance-like state. It is possible that the chaotic and confusing movements disorient the rabbit. Once the rabbit has been disabled, the weasel promptly jumps on the rabbit’s back and delivers a powerful bite to the back of the neck, instantly killing the rabbit.
Wild weasels and stoats practise this skill by playfully ambushing each other when they are young.

Long-tailed weasels, despite their cute appearance, are notorious for their vicious temper. Being a carnivore that prefers fresh meat, it actively hunts and collects food. Despite seeking fresh food, the weasel also exhibits a curious behaviour of storing carrions, which is often only eaten in times of food shortages. This behaviour leads to the weasel going on killing sprees just because they can. Long-tailed weasels have also been observed lapping up blood from the wounds they inflict, and enjoys making their nest from the fur of their victims.