Little penguins spend their days finding food at sea. With the help of location-tracking devices, researchers have found out that the smallest species of penguin tends to travel the sea in groups, and may dive at the same time while hunting fish.
Little penguins, also known as fairy penguins or blue penguins, are found in southern Australia, New Zealand and the Chatham Islands. Often they live on islands safe from foxes and feral cats. The penguins spend their day hunting for fish and crustaceans at sea, and come back to land as the Sun sets, to sleep in burrows.
It is difficult to observe bird behaviour at sea, so to work out how penguins find food, Maud Berlincourt from Deakin University turned to technology. A very small and light location-tracking device that also measures depth allowed her to collect data on the penguins at sea. The device was put on the back of the birds like a little backpack, and black waterproof tape kept it attached to their slick feathers.
Each penguin swam around with their backpack for a day, and then Maud collected it again at night. “We are monitoring a breeding colony on the eastern coast of Victoria at London Bridge. Those penguins are already sitting on eggs and some of them have chicks right now,” says Maud. “It’s a lot of work. I have spent many days and nights in the field waiting for the birds to come back with their devices.”
Maud collected data over 22 days, and with only a few penguins each day wearing the device. She found that they went to sea to hunt for about 15 hours during the day, and travelled around 40 kilometres. That’s at least an eight hour hike for us people.
Between 30 and 50 little penguins would leave each day to find food, and only about four would be wearing the device. Even though Maud was only tracking a few penguins at a time, she found them hanging out together quite a lot. On average, about 85% of tracked penguins would spend at least some time walking, swimming or diving near other tracked penguins. Almost half of the time, penguins swimming together would also dive at the same time.
These results suggest that little penguins look for food in groups, and might cooperate as they hunt fish. Does a penguin always look for food with the same feathered friends? More research is needed to find out.
In what century was the Gregorian calendar (the calendar we use today) introduced?
What is the glowing wire inside an electric light bulb called?
What fluid is produced from the sudoriferous glands in people?
What is the Ebola disease caused by? Is it a) a virus, b) a bacterium or c) a fungus.
What is a baby elephant also known as?
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Fill a glass with water and another with Ribena, right to the brim. You'll also need a card.
Place the card over the glass of Ribena.
Turn the glass upside down.
A neat trick! Take your finger off the card, and the liquid should stay inside the glass.
Place the glass of Ribena over the glass of water, so the card is all that is separating the two liquids. Carefully move the card to allow liquid to slowly flow through the gap.
The water has risen to the top glass, although there has been a bit of mixing.
You will need
Two small, identical glasses
Water
Ribena concentrate (a blackcurrant drink), or another syrupy concentrate
Piece of thin, strong card, big enough to cover the top of one of the glasses
Flat surface somewhere where spills are okay, like outside or next to the sink
What to do
Put the glasses on the flat surface.
Fill one glass with water, right to the brim.
Fill the other glass with Ribena, right to the brim, and place the piece of card over the top of the glass. Make sure the card covers the whole top of the glass, with no gaps.
Gently hold the card in place with your fingers and pick up the glass. Try not to press down on the card, just hold it flat. Turn the glass upside down.
If you like, you can try a neat trick here. Keep the glass upside down and take your fingers off the card. The liquid should stay in the glass and not leak out! Seeing as Ribena can stain, make sure to do this over a sink or outside, just in case it spills.
Place the upside down glass of Ribena on top of the glass of water, so the card is sandwiched between the two glasses.
Hold the top glass still and slowly, gently slide the card to one side. You are trying to make a small gap where the two liquids can move between the glasses. The gap between the edge of the card and the rim of the glasses should be very small, only about a millimetre.
Watch the liquids flow through the small gap.
The liquids are slowly swapping places! Depending on the size of the glasses and the size of the gap, it might take half an hour to swap completely. Watch your glasses to see if water is collecting in the top glass, and Ribena is flowing into the bottom glass.
To clean up, pick up both glasses and hold them over the sink or outside. Turn them sideways, then slowly move them apart so the liquids flow out without a big splash.
If your syrup swap didn’t work out, try it again and change the size of the gap between the card and the rim of the glass. Making it smaller should stop the liquids mixing. Try to avoid air bubbles by making sure each glass is full to the brim.
What’s happening?
The first neat trick is that you can put a card over the rim of a glass of liquid, turn it upside down and the liquid doesn’t just rush out. This happens because the liquid seals the space between the card and the glass, so air can’t get in. When you flip the glass over, the air around you pushes on the card, keeping the liquid in place. Air pressure is surprisingly strong. There’s about a kilogram of weight from the air pushing on your thumb right now! The air pushes upwards more than the weight of the water pushes downwards.
When you put the glasses on top of each other and move the card, the liquids can flow between the two glasses. The direction the liquids go is based on density. A litre of Ribena weighs more than a litre of water, so Ribena is more dense. The dense Ribena will flow into the bottom glass, while the less dense water rises to the top glass.
Why don’t the liquids mix? Ribena and water mix easily when you stir them. But with only a small gap to flow through, the Ribena flows down so slowly that it doesn’t stir up the water as it moves. If the gap is too big, the water and Ribena do swirl around and mix more.
Try repeating this activity using vegetable oil in the bottom cup and water in the top cup. Because oil and water do not mix, you should get an awesome effect as they totally swap places.
Applications
If you visit the south-east coast of Australia, you might spend time at the popular tourist destination, the Gippsland Lakes. These freshwater lakes are close to the salty sea, but were once separated from it by sand dunes. But because they make good harbours for boats, many of the lakes have been opened to the sea.
With the liquids able to flow between sea and lake regularly, saltwater has entered the freshwater habitat. Saltwater is more dense than freshwater, so it tends to lie on the bottom. This layering of water is called stratification, and means the lakes now have warm freshwater on the top and cold saltwater on the bottom. Many freshwater plants and animals are struggling with this change in their habitat.
Deep lakes are often stratified, or layered, not because of saltwater, but because of temperature. Cold water is denser than warm water. So lakes often have a layer of warm water on the top with cold water underneath, especially if the lake is still and the layers don’t mix. This can be important for fish, because some species live in warm water while others need cold water.
Layering can cause problems too. Because the layers do not mix, the cold bottom layer of water in the lake can run low on oxygen, and coldwater fish may die. Strong winds and the changing seasons during the year can help mix the water up a bit, and bring much-needed oxygen down below.
Imagine sitting in a car that drives itself. Britain announced it will try self-driving cars next year, and manufacturers say they could be for sale by the year 2020. How can cars drive themselves? Watch the video below to find out with A Week in Science by the RiAus.
Quiz answers
The Gregorian calendar was introduced in the 16th century (the 1500s).
The filament is the glowing wire in an electric light bulb.
Sweat is produced from the sudoriferous glands.
a) The Ebola disease is caused by a virus.
A baby elephant is also known as a calf.
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