Friday, 24 December 2010


An echidna of the Tachyglossus aculeatus species
A short beaked echidna
(Tachyglossus aculeatus)
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Monotremata
Family: Tachyglossidae
Species: 4 surviving species (Zaglossus attenboroughi, Zaglossus bruijnii, Zaglossus bartoni & Tachyglossus aculeatus)
Common Name(s): Echidna, Spiny anteaters
Conservation Status: All species of the Zaglossus genus are critically endangered. T. aculeatus is listed as "Least Concern".

No, contrary to what many will think, the creature depicted on the image above is not a hedgehog but an animal commonly known as Echidna.

Echidnas are animals belonging to the family Tachyglossidae, and along with the platypus, they are the only surviving members of the monotreme order,  the only mammals that lay eggs instead of giving birth to live young. As of today, there are four surviving Echidna species, that can be found in New Guinea and Australia.

Echidnas are classified into three genera, the Zaglossus, the Tachyglossus and the Megalibgwilia. Let's first see the four surviving species.

First, we have the three surviving Zaglossus species, all endemic to New Guinea, which are:

1) Western long-beaked echidna (Zaglossus bruijni), inhabiting the highland forests. It can be found in the Bird's Head Peninsula and Foja Mountains of West Papua and Papua provinces, Indonesia, respectively, in elevations of 1,300 to 4,000 meters (4,300 and 13,100 ft). The species is absent from the southern lowlands and north coast. Its prefers habitats are alpine meadow and humid montane forests. Recent data indicate that small populations of the species may also exist in the Kimberley region of Australia
Zaglossus bruijni (Western long-beaked echidna) Distribution
Western long-beaked Echidna Distribution

Z. bruijni primarily feeds on earthworms. It reaches weights of up to 16.5 kilograms (36 lb) and  has an elongated snout that turns downward. The spines are almost indistinguishable from its long fur. It is distinguished from the other Zaglossus species by the number of claws on the fore and hind feet, three and or rare occasions four. It is the largest surviving monotreme species.

It is listed as Critically Endangered with a seemingly declining trend. Its numbers have declined due to human activities, including habitat loss and hunting. It is considered a delicacy, and despite commercial hunting being banned by the Indonesian and Papua New Guinean authorities, traditional hunting is still permitted. The good news is that a January 2013 expedition, led by Conservation International, discovered a new population of the species as part of what they described as a "lost world" of wildlife in the Foja Mountains of Papua Province, Indonesia.

Western long-beaked echidna (Z. bruijni)
A Western long-beaked echidna

2) Next, we have Sir David's long-beaked echidna (Zaglossus attenboroughi), which was first described in 1961 and prefers higher habitats than Z. bruijni. does. It is also known as Attenborough's long-beaked echidna or the Cyclops long-beaked echidna. It's named after Sir David Attenborough, a popular English broadcaster and naturalist, best known for writing and presenting the Life series

Sir David's long-beaked echidna (Zaglossus attenboroughi) Distribution
Sir David's long-beaked Echidna Distribution 

Z. attenboroughi lives in the Cyclops Mountains in Papua province of Indonesia near the cities of Sentani and Jayapura. It's the smallest species of the genus, being closer in size to the short-beaked echidna than are other Zaglossus members. Males are larger than females, and can be differentiated by the spurs on their hind legs. Their weight ranges from 5 to 10 kilograms (11 to 22 lb). They mainly feed on earthworms, termites, insect larvae and ants.

The species is critically endangered due hunting and habitat loss. Actually, in the 1900s, it was believed to have gone extinct until some of their "nose pokes" were found in the mountains of New Guinea. These "nose pokes" are very distinctive and represent the echidna's feeding techniques.

3) Finally, we have the Eastern long-beaked echidna (Zaglossus bartoni). It is also known as Barton's long-beaked echidna and can be mainly found in Papua New Guinea, at elevations of 2,000 to 3,000 meters high (6,600 and 9,800 ft).

Eastern long-beaked echidna (Zaglossus bartoni) distribution
Eastern long-beaked echidna distribution

Currently, there are four identified Z. bartoni subspecies:
  • Z. bartoni bartoni 
  • Z. bartoni clunius 
  • Z. bartoni smeenki
  • Z. bartoni diamondi

The subspecies are primarily distinguished by small differences in their body size whith the population of each subspecies being geographically isolated.

Z. bartoni mainly eat insects ants, ticks, earthworms, termites and larvae. Similarly to the other Zaglossus species, Eastern long-beaked echidna is critically endangered, with deforestation and habitual loss being the leading factors.

The last surviving echidna is the Short-beaked echidna, which belongs to the Tachyglossues genus (Tachyglossus aculeatus). The species thrives throughout Australia, where it is the most widespread native mammal, and in coastal and highland regions of southwestern New Guinea, where it is commonly known as the mungwe in the Daribi and Chimbu languages.It occurs in almost all environments of its habitat, from the snow-clad Australian Alps to the deep deserts of the Outback. Essentially, any place with ants and termites (its primary source of food) is perfect for T. aculeatus.

Short-beaked echidna (Tachyglossus aculeatus) distribution
Short-beaked echidna distribution

It is smaller from the Zaglossus echidnas and has longer hair. As suggested by its common name, it is easily recognized by its short beak. At the moment, there are five recognized short-beaked echidna subspecies:
  • T.aculeatus acanthion, found in Northern Territory and Western Australia.
  • T.aculeatus aculeatus, found in Queensland, New South Wales, South Australia and Victoria.
  • T.aculeatus. lawesii, found in coastal regions and the highlands of New Guinea, and possibly in the rainforests of Northeast Queensland.
  • T.aculeatus multiaculeatus, found on Kangaroo Island.
  • T.aculeatus setosus, found on Tasmania and some islands in Bass Strait.

The subspecies differ from one another in their hairiness, spine length and width, and the size of the grooming claws on their hind feet

T.aculeatus is very common throughout Australia and New Guinea, and is currently listed as of Least Concern. Although there are incidents of localized extinctions due to habitat destruction, the species is not believed t be under any immediate threat.

Shrt-beaked echidna spines and fur close-up
T.aculeatus spines and fur close-up

There also many recorded Echidna species that have gone extinct:
  • Zaglossus robustus
  • Zaglossus hacketti
  • Megalibgwilia ramsayi from Late Pleistocene sites in Australia 
  • Megalibgwilia robusta from Miocene sites in Australia 
These species have been extinct for millions of years and are only known from fossils.

Image showing a short beaked echidna
A Short-beaked echidna

They are small animals slightly resembling the South American anteaters, hedgehogs and porcupines, without however being closely related to any of them. Echidnas have short and strong limbs, equipped with large claws used for digging. They have tiny mouths and toothless jaws. When threatened, they have the ability to curl into balls, protruding their spines to all directions.

Video showing a short-beaked echidna building a defensive burrow on French Island, Victoria, Australia.

Their snouts are long -except for T.aculeatus- and slender. Like the platypus, their snout has electroreceptors. However, in comparison to the platypus which has more than 40.000 such electroreceptors, they have way less, for instance the long-billed echidna has 2000 and the short-billed echidna only 400.

A short  beaked echidna curled into a ball

Thanks to their low metabolism and high stress resistance, they are long-lived for their size. In captivity, the longest recorded lifespan is 50 years, with anecdotal accounts of individuals reaching the age of 45 years in the wild.

Image showing the skeleton of a short-beaked echidna
Short-beaked echidna skeleton

Their diet mainly consists of ants and termites, while the Zaglossus species are also reported to eat worms and insect larvae. When feeding, they use their long and sticky tongue which protrudes from the snout

Along with the platypus, they are the only known mammals to actually lay eggs instead of giving birth to young ones.

Breeding season begins in late June and extends through September. Males form lines up to ten individuals long, with the youngest echidna trailing last, that follow the female and attempt to mate. During the mating season an echidna may switch between lines. This is known as the "train" system.

Females lay a single soft, leathery egg, 14-22 days after mating, which is deposited directly into her pouch. It takes about ten days for the embryos to hatch. Echidna babies - called puggles - are born hairless and spineless

Video showing an echidna hatching from its egg. Awesome!

Afterwards the puggles (as young echidnas are called) start to suck milk from the mother's porous milk patches (monotremes don’t have nipples) and stay in the pouch from 45 to 55 days. During this period, the spines gradually develop both in number and size. Then, the mother digs a nursery burrow where the puggle is deposited. She leaves and returns every five days to milk it, until it's weaned 7-12 months later.

Video showing an Echidna Puggle. Never has something so ugly been so cute !

Conservation Status
As of today, all the surviving Zaglossus species are listed by the IUCN as critically endangered while the short-beaked echidna (T. aculeatus) is listed as being of Least Concern. As aforementioned, the main threat s for the endangered species are habitat loss and traditional hunting.

Interesting facts about Echidnas
- Male echidnas are known for having a four-headed penis. During intercourse, the two heads on the one side "shut down" and don't grow in size, while the other two heads release sperm inside the female's two branched reproductive tract. The heads are swapped each time the male echidna copulates. When erect, the penis is about 7 cm long and when not in use, it is retracted inside a preputial sac in the cloaca. The shaft is covered with penile spines.
Video showing the four headed penis males have!
- They show little to no interest in mating while in captivity. Actually, noone has ever seen a male ejaculate. There have even been attempts, to force ejaculation through the use of electrical stimulation to collect semen samples, but this only resulted in the penis swelling
- In the past, it was believed that echidnas did not enter REM sleep, however recent research showed this to be false. Having said that, they only enter REM sleep when the ambient temperature is around 25°C (77°F). At temperatures of 15 °C (59 °F) or lower and 28 °C (~82 °F) or higher, REM is suppressed.
- They are named after the "Mother of monsters" in Greek mythology, despite not bearing any kind of resemblance to the mythological creature. Echidna (Ancient Greek: Ἔχιδνα, "she viper") was half woman, half snake. She was killed by Argus Panoptes, a hundred-eyed giant who served Hera.
- An echidna appears on the reverse of the Australian 5-cent coin.
- Knuckles is a red echidna appearing in the popular video game series, Sonic the Hedgehog.
- Millie the Echidna was one the three mascots of the 2000 Summer Olympics.

Image of a spikeless, 1 month old echidna baby
One month old echidna baby - Unspecified Species
Credit: Australia Zoo

Selected References & Further Reading
- Werneburg, I., & Sánchez-Villagra, M. (2011). The early development of the echidna, Tachyglossus aculeatus (Mammalia: Monotremata), and patterns of mammalian development Acta Zoologica, 92 (1), 75-88 DOI: 10.1111/j.1463-6395.2009.00447.x
- Proske U, Gregory JE, & Iggo A (1998). Sensory receptors in monotremes. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 353 (1372), 1187-98 PMID: 9720114
- FLANNERY, T., & GROVES, C. (1998). A revision of the genus Zaglossus (Monotremata, Tachyglossidae), with description of new species and subspecies Mammalia, 62 (3) DOI: 10.1515/mamm.1998.62.3.367
- Helgen, K., Portela Miguez, R., Kohen, J., & Helgen, L. (2012). Modern occurrence of the Long-Beaked Echidna Zaglossus bruijnii in the Kimberley region of Australia ZooKeys, 255, 103-132 DOI: 10.3897/zookeys.255.3774
- Grigg GC, Beard LA, Barnes JA, Perry LI, Fry GJ, & Hawkins M (2003). Body temperature in captive long-beaked echidnas (Zaglossus bartoni). Comparative biochemistry and physiology. Part A, Molecular & integrative physiology, 136 (4), 911-6 PMID: 14667854
- Nicol SC, Andersen NA, Phillips NH, & Berger RJ (2000). The echidna manifests typical characteristics of rapid eye movement sleep. Neuroscience letters, 283 (1), 49-52 PMID: 10729631
- Griffiths, Mervyn (1978). The biology of the monotremes. New York: Academic Press. ISBN 0123038502.
- Phillips, M., Bennett, T., & Lee, M. (2009). Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas Proceedings of the National Academy of Sciences, 106 (40), 17089-17094 DOI: 10.1073/pnas.0904649106
- Morrow, G., & Nicol, S. (2012). Maternal care in the Tasmanian echidna (Tachyglossus aculeatus setosus) Australian Journal of Zoology, 60 (5) DOI: 10.1071/ZO12066
- Johnston SD, Smith B, Pyne M, Stenzel D, & Holt WV (2007). One-sided ejaculation of echidna sperm bundles. The American naturalist, 170 (6) PMID: 18171162

1 comment:

  1. These guys are definitely NOT arthropods!!