【明報專訊】Sometimes white, sometimes grey

In order to survive in the frigid (寒冷的) Arctic region, Arctic foxes moult (換毛) twice a year to keep their fur in camouflage (保護色). During winter, their fur is entirely white, enabling them to blend in with the ice and snow. During summer, it becomes brown or grey, matching the surrounding rocks and dirt along the tundra (凍原) which they frequent. Being "invisible" protects animals from predators. For Arctic foxes, camouflage also helps them to effectively hunt rodents, birds and even steal eggs from bird nests.

Survival of the fittest

Arctic foxes have shorter legs, shorter necks and smaller ears as compared to other species of fox. This low surface area to volume ratio helps them to reduce heat loss from the body. In addition, the long fluffy tail provides insulation. When the Arctic fox sleeps, it curls up with the tail wrapping around itself like a blanket. The thick fur on the paws allows the animals to keep a grip on slippery surfaces, which is important for the fox to walk on ice or snow.

Burrow-living families

Arctic foxes dig their dens on hillsides or the riverbank (河岸). These dens have multiple entrances and a system of tunnels covering about 30 square metres. In a blizzard (暴風雪), they may tunnel into the snow to create shelter. When food is widely available in the summer, Arctic foxes collect and store the excess food in their dens for the winter. When food is abundant, a breeding pair can have as many as 19 cubs in a litter (胎), with normally 5-10 young produced on average. Both parents are responsible to rear the young. The cubs feed on the mother's milk during the first three weeks and rarely leave the den. As the cubs grow up and begin to take meat, the mother goes out to hunt as well. The cubs only emerge from the den after two to four weeks, when they are weaned (斷奶).

Competition between red foxes and Arctic foxes

Arctic foxes are specially adapted to the frigid clime (氣候帶). As the temperature rises, Arctic foxes are out-competed by their cousins, the more adaptable red foxes (赤狐). The Arctic foxes abandon dens used for generations and go in search of a new place to call home. Global warming also decreases the number of lemmings (旅鼠), which is an important food source for Arctic foxes.

Help stop illegal wildlife trade

In 2013, the Arctic Fox Den of Ocean Park's Polar Adventure received the arrival of a female Arctic fox, Mochi, which was confiscated by the Agriculture, Fisheries and Conservation Department in an illegal wildlife trade. Mochi established a family with Gochi and a litter of Arctic fox pups was born in 2014. Although it has resulted in the birth of those wonderful pups, we should be reminded not to engage in the trading or purchase of illegally sourced wildlife as pets.

Text & photos: Ocean Park Hong Kong

■Glossary

frequent (v) 常常聚居

excess (adj) 多餘的

abandon (v) 離棄

confiscate (v) 充公

[Smarties' Power English 第210期]