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Dung Beetles Navigate Using the Milky Way

By Magdeline Lum

Dung deetles navigate using the Milky Way, and scientists analyse a dead whale’s ear wax to reveal its exposure to hazardous chemicals.

It’s that time of year of when research is acknowledged and awarded for making us laugh and then think. It’s the Ig Nobel season.

This year the winner of the joint biology and astronomy prize went to Prof Eric Warrant of Lund University and his colleagues for being the first to document the use of the Milky Way for orientation in the animal kingdom.

Warrant was born in Australia and married his love of physics and entomology in his PhD at the Australian National University. He studied the optics of the compound eyes of dung beetles.

Unlike the compound eyes of flies and butterflies, which are active during the day, the compound eyes of dung beetles are built for dim light. Most insects can see only the brightest stars in the night sky, but the dung beetles are able to make out the glowing band of the Milky Way across the night sky and use it as a navigation cue.

Warrant and his colleagues taped small hats made from black cardboard and clear material to the heads of the dung beetles. The black hats blocked the beetles’ view of the sky, and observed the dung beetles losing their way.

Dung beetles were then placed in a planetarium that simulated the Milky Way. When the Milky Way was being projected, the dung beetles were able to navigate but when it was not, the dung beetles could not find their way.

These days Warrant is studying how beetles navigate when there are other navigation cues present. For example, on nights when the moon is present, does this additional light compete for attention from the dung beetles? And during the day the Sun’s position in the sky provides navigational information through polarisation. Warrant is determining the importance of these different cues.

Whale Tale in Ear Wax

For the first time a wax plug from the ear of a dead 12-year-old blue whale has revealed its life story to researchers. Usually blood, faecal and blubber samples are collected but the information provided only apply to a short period of time.

The ear wax is also known as the whale’s earplug. It is made up of lipids, waxes and keratin, and builds up in layers from birth at a rate of two layers per year. Historically, scientists have used the whale’s earplug as a tool to determine the age of a whale in a similar way to counting tree rings.

Professor Sascha Usenko of Baylor University, Texas, and his colleagues wondered whether the earwax would be able to archive chemicals in its layers. They extracted an ear plug from a blue whale that died after a ship collided with it in 2007 off the coast of California.

The earplug was sliced, revealing 24 discrete layers – indicating that the whale was 12 years old. Samples were taken from each layer for analysis, and the results showed that the whale had been exposed to a range of chemicals, including pesticides and flame retardants, in its first year of life.

Many of these compounds have been banned for at least a decade, which suggests that the chemical exposure began during gestation and into nursing. They could have been stored within the mother’s fat stores before being passed on.

The researchers were also able to monitor hormone levels. Testosterone peaked at 10 years when the whale became sexually mature. This was followed by a rapid increase of the stress hormone cortisol. Researchers infer that this may have been due to competition with other males for a mate or from trying to form social bonds. However, stress factors like weaning, food availability, pollution and noise could not be discounted.

There are now hopes that this new test will be able to provide a new way of understanding how whales live today compared with whales that lived in the past. Older samples of whale ear wax can be analysed to look for the effects of pollution and the introduction of specific chemicals and pesticides over periods of time.