Top 10 unusual animals

On 20 December 2013, the United Nations General Assembly decided to proclaim 3 March as World Wildlife Day as part of efforts to celebrate and raise awareness of the world's wild fauna and flora.

The day is an opportunity to raise awareness of the multitude of benefits that the conservation of these forms of life brings to humanity. It also reminds us of the urgent need to step up the fight against crime against the environment and human-induced reduction of species, which have wide-ranging economic, environmental and social impacts. Given these various negative effects, Sustainable Development Goal (SDG) 15 focuses on halting biodiversity loss.

Sustainability for all is using World Wildlife Day to highlight some of the most fascinating species of animal with which we are lucky enough to share our planet. Discover our top 10 unusual animals!

If there was ever a creature with such fascinating biological characteristics it would be the axolotl — also known as the Mexican walking fish (Ambystoma mexicanum). For example, it has been discovered that if an axolotl loses a limb, these amphibians are able to regenerate it in a matter of weeks, with all the bones, muscles, and nerves in the right places. This makes the axolotl one of the most fascinating creatures on our planet.

A salp is neither a fish, nor a jellyfish. Phylogenetically, it forms part of a group of animals called tunicates. Salps are hermaphrodites and their reproductive cycle is characterised by alternation of generations.

Completely harmless, these long chains of transparent organisms have a vital function: their gigantic colonies are able to absorb a large amount of CO2 and filter it out of the ocean, contributing to the oceanic carbon cycle, which has a significant impact on climate change.

This amphibian, which has been named Hyalinobatrachium yaku, differs from other glass frogs due to the dark green spots on its head and body, as well as having a longer call (up to four seconds) with a higher frequency. However, this creature's most remarkable feature is that it has a transparent pericardium, meaning that its heartbeat is visible through its skin. It is the glass frog's transparent skin that earns it its place in our top ten unusual animals.

The sun bear (Helarctos malayanus) is a species in the family of bears found in the habitats of the Southeast Asian tropical forests and is listed as Vulnerable on the International Union for Conservation of Nature (IUCN) Red List. Global sun bear populations are estimated to have decreased by 30 % over the past 3 generations of bears, in addition to suitable sun bear habitats having been drastically reduced due to deforestation.

The sun bear is the smallest of the bear species, with adults standing approximately 120 to 150 centimetres tall. They are characterised by their short black coat with a whitish or yellowish crescent-shaped spot on their chest.

This Australian songbird has the extraordinary ability to mimic a wide variety of sounds with incredible accuracy. It is capable of imitating 20 species of birds and their calls and has even been heard mimicking car alarms and chain saws.

This creature is a marine fish belonging to the seahorse family. Its name is derived from the long leaf-like protrusions all over its body, making it resemble the mythical dragon.

Our top unusual animals includes another ocean-dweller with a mythological appearance. The narwhal's horn resembles that of a unicorn. This horn is actually a protruding tusk that it uses to hit and stun small fish that it then devours.

The pangolin is a solitary animal with nocturnal habits. When it feels threatened, it covers its head with its front legs, leaving only its scales able to be seen. Pangolin scales are in high demand in some Asian countries such as China and Vietnam, where they are used in traditional medicine as remedies for asthma, rheumatism and arthritis.

All eight existing species of pangolin are listed as Threatened and two of these have been listed by the IUCN as Critically Endangered, meaning that these animals are threatened with extinction.

The Tasmanian devil earned its popular name thanks to the size and power of its jaws, together with its characteristic carnivorous ferocity. The last remaining wild populations of this carnivorous marsupial are found in Tasmania, Australia. In 2008, it was included as an Endangered species on the IUCN Red List.

Last but not least in Sustainability for all's top unusual animals is this goat that lives in the Himalayas and is famous for its big horns. The markhor stands just under a metre and a half tall, weighing in at around 100 kilos. It is one of the tallest members of the goat family, surpassed only by the Siberian mountain goat. The males have a pair of large twisted horns resembling a corkscrew, which can grow to more than one metre in length.