“Small enough to fit in your hands but too dangerous to hold” is a good description of the hedgehog. Though small, it is able to protect itself from attack or harm. Thousands of stiff, sharp spines cover the animal’s back and sides. Even though spines provide the hedgehog with effective protection, the animal’s most striking characteristic is its practice of curling up into a tight ball, with its spines sticking out in all directions. The hedgehog curls up if disturbed or frightened—only the strongest animals can open it. It also sleeps in this position, so it is rarely caught unprotected.

Hedgehogs can live in a wide range of climates and lands in East Africa. They must have dry shelters on well-drained soil and a good supply of insects. Nairobi, the capital of Kenya in East Africa, meets these habitat conditions, where hedgehogs are reported to be abundant. A hedgehog uses a small home range with an approximate 120-yard radius (半径范围) from its nest. The hedgehog makes loud noises if its range is invaded by another animal.

The hedgehog wakes up at dusk and begins its activities alone. It uses regular pathways, walking along on its short legs searching for food. A hedgehog will eat about one-third of its body weight in one night. Its favorite foods are insects, earthworms and snails, making it a welcome guest in many gardens—it is even kept as a pet. It is also known to eat eggs, small mammals, birds, frogs, reptiles, and roots. Although not completely immune to poison, hedgehogs have enough resistance to allow them to eat poisonous snakes.

Red squirrels (松鼠) , a kind of animal once lost from their native woodlands, have been returned to the north-west Highlands, early results of a reintroduction (重新引进) project show.

The new population has naturally increased since they were reintroduced to north-west Scotland last year. The animal had disappeared as a result of the reduction of forests, as well as illness and competition from the introduced non-native grey squirrel. However, Trees for Life—the organization behind the project—is hopeful that red squirrels will continue to add to their 138,000 number and continue their increase.

“Early results shows that this could be a real wildlife success story. The new squirrel populations are not only living in their new homes, they are also starting to spread out into new areas, with squirrels being sighted as far as 15km away, “said Becky Priestley, Trees for Life’s wildlife officer.

The first relocation began in the spring of 2016, through to this year, when the first 33 squirrels from Inverness-shire and Moray were set free at Shieldaig in Wester Ross. Another 22 were set free at the Coulin estate, next to Beinn Eighe, plus 30 at Plockton, which is partly owned by the National Trust for Scotland.

The red squirrel, found throughout Eurasia, has experienced a great population reduction in recent years. In 2007, just 25,000 could be found throughout the UK after a one-time high of 3.5 million. This is often because of the fact that their grey cousins have a larger appetite (食欲) and eat most of the food in the forest. Reds are also more likely to be influenced by viruses (病毒) than greys, dying up to 25 times quicker.

Grey squirrels first came to England from North America in 1876 as a decorative species. However, it was not until 1930 that the damage they did was realized, when it was almost too late for the reds.

Now, though, red squirrels appear to naturally take over their land again. During 2016, they spread beyond Shieldaig, with one sighting eight miles away beyond Loch Torridon. One was seen recently near Nostie, about five miles from the release site, and there have been sightings further.

A butterfly's wings can have many jobs besides keeping the insect in the air. They may be called on to attract mates, to warn potential enemies to stay away, to do other animals or even to provide disguise（伪装）.

All of these roles, though, depend on their colouration—which is unchanging. This plays into the idea that butterfly wings are dead tissue, like a bird's feathers or a mammal's hair. In fact, that is not true. For example, in some species males' wings harbour special cells that release chemicals which attract females.

Nanfang Yu, a physicist at Columbia University, in New York, has been looking into the matter. One of his interests is the optical（光学的）properties of biological materials. That has led him to study butterfly wings in more detail. And, in cooperation with Naomi Pierce, a butterfly specialist at Harvard University, he has now shown, in a paper published this week in Nature Communications, that butterfly wings are, indeed, very much alive.

Initially, Dr Yu and Dr Pierce wanted to know how the insects keep their body temperatures up without their wings overheating.

Unlike birds and mammals, butterflies do not produce enough internal heat to metabolize（新陈代谢）. Instead, they rely on outside heat sources—usually the sun—to bring their bodies up to speed. But their wings, being thin protein membranes（膜）, have a limited thermal capacity. Those wings can therefore overheat quickly if the insects are exposed to the sunlight too long, or, oppositely, can cool down too rapidly if they are flying through cold air.

In their experiments, the two researchers used a laser（激光）to heat up spots on the wings of dozens of butterfly species. When the temperature of the area under the laser reached 40℃ or so, the insects responded within seconds by doing things that stopped their wings heating up further. These actions included a butterfly turning around to minimize its exposure to the laser, beating its wings or simply walking away.