Echidna (family Tachyglossidae)
Echidnas, belonging to the family Tachyglossidae, are unique monotremes native to Australia and New Guinea, known for their egg-laying reproductive method, which distinguishes them from most mammals that give birth to live young. Often referred to as spiny anteaters, echidnas are evolutionary relics that exhibit both mammalian and reptilian traits, including a cloaca for excretion and reproduction. They lack teeth and utilize a specialized snout to capture prey such as ants and termites with their long, sticky tongues. There are four recognized echidna species, with the short-beaked echidna being the most widespread.
Echidnas hold cultural significance for Indigenous Australian peoples, serving as a food source and appearing in various forms of traditional art and mythology. The long-beaked echidnas of New Guinea are critically endangered, facing threats from habitat loss and hunting, while the short-beaked echidna is better protected in Australia. Research on echidnas may provide insights into early mammalian evolution, making them important not just ecologically, but also scientifically. Their distinct characteristics and cultural relevance contribute to their status as iconic animals of Australia.
Echidna (family Tachyglossidae)
The echidna (ih-KID-nuh) is a type of primitive mammal found in Australia and New Guinea. Echidnas belong to the taxonomic family called Tachyglossidae. These animals are also monotremes. Monotremes, which are limited to platypuses and echidnas, are a group of mammals that lay eggs rather than give birth to live young as most other mammals do. Echidnas are considered the most primitive living mammals and may be the oldest surviving mammal species. They are also sometimes called spiny anteaters, though they are not part of the anteater family.
Characteristics and Species
The echidnas are considered evolutionary oddities, which is reflected in the name echidna itself. They are named after a monster from Greek myth called Echidna, who was half-human and half-snake. As echidnas are generally very passive animals, the name was meant to reflect the perception that they have both mammalian and reptilian traits rather than to indicate any type of threatening behavior.
In addition to the evolutionary relic of laying eggs, echidnas lack teeth and instead use their highly modified snout as both a mouth and nose. Monotremes have a number of other unique traits that separate them from other mammals. They have a single opening called a cloaca (similar to that found in reptiles) that they use to urinate, defecate, and reproduce. In fact, the name monotremes comes from the Greek words for "single hole" in reference to the cloaca. Monotremes also sense their prey through electroreception, which means that they can sense the electrical fields of the insects and worms on which they feed. Monotremes are the only land-based mammals to have developed electroreception, which is usually found in fish and insects. They also have the lowest body temperature of any type of mammal. Further, all echidnas have sharp defensive spines along their backs and spurs on their hind legs. The spurs are used to help mark their territories and communicate their intention to breed.
Like marsupials, to which they are not closely related, they carry their young in a pouch. Unlike marsupials, however, echidnas lay a single egg, which remains inside the female's reproductive system. When it reaches the size of a grape, it moves into the upside-down pouch of the mother, where it remains for ten days. Unlike other mammals, female echidnas do not have teats to feed milk to their young. Instead, after hatching, a single baby echidna (which is called a puggle), will suckle on specialized hairs onto which milk has been secreted from glands.
There are four surviving species of echidna, which are placed into one extinct and two surviving genera. The species from the genus Megalibgwilia are known only from fossils, while there is one known species of Tachyglossus and three living species in the Zaglossus genus. The most common species is the short-beaked echidna (Tachyglossus aculeatus), which is found throughout Australia and in parts of New Guinea.
The primary differences between the short-beaked echidna of the genus Tachyglossus and the long-beaked species of the genus Zaglossus are the length of their snouts (or beaks), their diets, their sizes, and their ranges. The snouts of short-beaked echidnas are roughly two-thirds the size of their long-beaked cousins. The long-beaked echidnas, which are restricted to New Guinea, are typically larger than the short-beaked echidnas. In addition, long-beaked echidnas primarily consume earthworms, while the short-beaked echidnas subsist on ants and termites. Echidnas use their long tongues and sticky saliva to capture their prey, which they grind by pressing their tongues to the bottom of their mouths. Echidnas are unable to bite or chew.
The three species of long-beaked echidna are the eastern long-beaked echidna (Zaglossus bartoni), the western long-beaked echidna (Zaglossus bruijni), and Sir David's long-beaked echidna (Zaglossus attenboroughi). Scientists have never seen Sir David's long-beaked echidna in the wild. The only evidence of its existence is one specimen collected in 1961, some droppings, and a few recorded observations by tribesmen.
Cultural and Scientific Importance
Echidnas were an important animal to the indigenous Aboriginal peoples of Australia. They served as a food source for many tribes, and they were often incorporated into the art and mythology of various Aboriginal groups. Engravings of echidnas are found at Ku-ring-gai Chase National Park near Sydney, while they also appear in the rock art of Arnhem Land in northern Australia. In addition, Aboriginals used the echidna as a totem in their native rituals.
Echidnas are an iconic animal of Australia. They are depicted on the country's five-cent piece and are regularly featured in contemporary Aboriginal art. In addition, New Guinea's long-beaked echidnas are regarded as such evolutionarily distinct animals that the Zoological Society of London's EDGE (Evolutionarily Distinct and Globally Endangered) Conservation Program uses them as part of its logo.
Like the platypus, the echidna is considered a living relic. Scientists believe that monotremes display many of the evolutionary characteristics adopted by early mammals as they transitioned away from reptiles. Their ability to lay eggs and the presence of cloacae are considered more reptilian in nature. Nonetheless, like all mammals, they have hair rather than scales, three middle ear bones called ossicles, a highly developed portion of the brain called the neocortex, and mammary glands. Scientists hope that the study of echidnas will help them understand how mammals first evolved.
All three of the long-beaked echidna species—which are exclusive to New Guinea—are critically endangered. Traditionally, many indigenous groups in New Guinea had taboos against eating echidnas. This helped to ensure their survival after the region was colonized. However, as these cultures moved away from traditional practices and toward more Westernized customs, they have increasingly regarded echidnas as valuable forms of protein. As New Guinea has no large native mammals, the island's three species of echidnas did not develop a fear of predators, meaning they are easily caught by both humans and introduced predators. While their spines offer some protection, unrestricted hunting has led to the extinctions of many local populations, particularly near human-populated areas. The short-beaked echidna has fared better in Australia, where there are a number of protective programs in place. As of 2022, Sir David’s long-beaked echidna and the western long-beaked echidna were both listed as critically endangered species. The eastern long-beaked echidna was listed as vulnerable, while the short-beaked echidna was not endangered.
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