Tachyglossidae

Diversity

The family Tachyglossidae consists of two genera of echidnas, Tachyglossus and Zaglossus . Echidnas share the order Monotremata with platypuses , as these are the only extant egg-laying mammals. The genus Tachyglossus defines the species of short-beaked echidnas while Zaglossus is composed of the long-beaked echidnas. The family has similar morphological characters, but long-beaked echidnas are larger in size, have longer snouts and less spikes than its sister taxa of short-beaked echidnas. Long-beaked echidnas are also located solely in New Guinea, whereas short-beaked echidnas are found in New Guinea, Australia, and Tasmania. The genus of short-beaked echidnas is composed of the single species T. aculeatus and its subspecies whereas long-beaked echidnas have the following three species: Z. attenboroughi , Z. bartoni , and Z. bruijni .

Geographic Range

Short-beaked echidnas are distributed throughout the entire continent of Australia including Tasmania and eastern and southern New Guinea. Long-beaked echidnas are endemic to New Guinea but fossil records suggest populations were once in Australia.

• Biogeographic Regions
• australian australian
  • native native

Habitat

Short-beaked echidnas can have a large range of habitats, so long as the substrate is suitable for their burrowing lifestyle. Long-beaked echidnas have a narrower range and are confined to New Guinea due to their need for a humid environment. Short-beaked echidnas can survive in more arid environments as their diet provides the moisture necessary for survival. Short-beaked echidnas can inhabit anywhere from temperate or tropical forests to sandy deserts. Both genera of echidnas have specialized feet for digging and burrow for shelter. There has been evidence of short-beaked echidnas temporarily residing in abandoned rabbit burrows for cover. Home ranges of echidnas is highly variable based on their location, but males' ranges are typically twice the size of that of a female’s. Overlap between ranges of two individuals may occur, but territory does not lead to hostility between the two. There is no home den that individuals continue to reside in, but nursery burrows may be constructed by females during reproduction periods.

• Habitat Regions
• temperate temperate
• tropical tropical

• Terrestrial Biomes
• desert or dune desert or dune
• savanna or grassland savanna or grassland
• forest forest
• rainforest rainforest

Systematic and Taxonomic History

Echidnas are closest related to platypuses as they are the egg-laying mammals and form the order Monotremata. Monotremes and marsupials make up the basal taxa of mammals, Theria- the non-placental mammals. Monotremes produce milk, but lack teats. Fossil records provide evidence that mammal ancestors dating back to 220 million years ago were able to suckle based on bone structure and muscle attachment. Monotremes diverged from the mammals around 190 million years ago and therefore lost the ability to suckle. It is hypothesized the loss of the soft palate to allow for sucking occurred as an adaptation to their diet of hard-shelled prey. The genus of short-beaked echidnas has the following synonyms: Acanthonotus , Echidna , Echinopus , Syphonia . The genus of long-beaked echidnas has the following synonyms: Acanthoglossus , Bruynia , Proechidna , Prozaglossus . The synonyms are a result of names that were once established but are now incorrect due to Principle of Priority.

Physical Description

Echidnas lay eggs and are therefore classified as monotremes along with platypuses , forming the basal taxa of mammals. Echidnas are covered in brown or black fur, with spines along the dorsal side of the body for protection. Short-beaked echidna spines are typically yellow, fading to black at the tip. Long-beaked echidnas have fewer spines that are white, gray, or black. Short-beaked echidnas can be 30 to 45 cm in length and weigh from 2.5 to 7 kg, with a beak approximately half the length of the head and a short tail, typically around or under 100 mm. Long-beaked echidnas are a little larger from 60 to 100 cm in length and weighing 5 to 10 kg and a beak length ranging from 100 mm to 150 mm. This length creates a downward curve in their beaks. While echidnas lack teeth, their extended snouts have pores for electroreception and sticky tongues to assist in achieving a meal. They have short stout legs with long claws for digging. Their hind feet are also pointed backward, which gives them an unusal gait. The hind feet also have a spur on the inner ankle. While in the monotreme platypus males have a venomous spur, both male and female echidnas have spurs without venom.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

Echidnas are typically solitary outside of mating. Males seek out females, and several follow her, forming what is colloquially called an "echidna train". Males then battle to for the opportunity to mate with the female.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Echidnas become sexually mature between 5 and 12 years of age. Breeding season occurs from July to August. Echidnas only have one young a year. They have one external opening called a cloaca for expelling waste and reproduction. Males have penises made for only copulation. The penis is bifurcated and forked at the end, giving the males a four-headed penis. Females produce one small, nearly round, leathery egg from the cloaca and transfer it directly to their pouch where it incubates for an average of ten days. Mothers prepare for hatching in this time by finding or digging a burrow. Observances of captive echidnas breeding in the Perth Zoo demonstrate nearly identical patterns to that of reproduction in the wild.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Male echidnas do not have parental investment so echidna mothers provide all care for their offspring. The young hatch pink and hairless, weighing only 0.3 g. Baby echidnas, called puggles, remain in the pouch for around 50 days, where they lap up milk. Echidnas do not have teats, but rather milk patches where milk simply leaks out. After 50 days, the mothers are able to leave the young in a burrow to forage for food. They return every 5 to 6 days to feed their offspring. When mothers leave the den, they cover the entrance with soil to keep their puggles safe from predation. Young echidnas become independent at one year old.

• Parental Investment
• female parental care female parental care

Lifespan/Longevity

Monotremes are considerably long-lived. Echidnas live up to 20 years in the wild and between 30 to 50 years in captivity.

Behavior

Echidna hind feet appear as if backwards on their body. This not only helps them to be more efficient diggers in their fossorial lifestyle, but also gives them a unique gait. This is described as rolling, and can be similar imagined as wobbling side to side. The articulation of the hind limb bones also allows echidnas to use their claws for grooming. Echidnas do go into torpor when they experience food shortages, dependent on season and climate. This occurs during the cold season, from April to July. Both body temperature and metabolic rate decrease. Short-beaked echidnas also enter torpor during times of food scarcity but these are short periods based on resources, not weather.

• Key Behaviors
• fossorial fossorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• aestivation
• solitary solitary

Communication and Perception

Due to the solitary behavior of echidnas, communication between individuals is rarely observed. Their sensory beaks have the potential for forms of electroreception and it has been hypothesized they may use vibrations and reception through their beak to communicate. Vocalizations are characterized as grunting, occurring when an individual is startled.

• Communication Channels
• acoustic acoustic

• Other Communication Modes
• vibrations vibrations

• Perception Channels
• tactile tactile
• chemical chemical

Food Habits

Echidnas lack teeth. Instead they have keratinous rows of spines on their palate to grind prey. Short-beaked echidnas have a sticky tongue that can reach up to 180 mm to catch invertebrate prey. The tongue becomes sticky from mucous secreted from their sublingual salivary glands. Short-beaked echidnas eat ants, termites, beetles, their eggs and larvae, and earthworms. Short-beaked echidnas in arid environments maintain water intake by consuming only termites. They forage for invertebrates by digging and often rip apart rotting logs with their claws.

Long-beaked echidnas diets are mainly earthworms and possibly other subterranean arthropods. This limiting factor is hypothesized to be a reason for the limited range of this genus. The tongue of long-beaked echidnas is not sticky and only extends about 2 to 3 cm from their elongated snout but they do have rows of keratinous spines for grinding prey.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

Predation

There are few native predators of short-beaked echidnas. They are mainly preyed upon by feral pigs, cats, foxes, and dogs. Young echidnas left in burrows can also face goannas and snakes. To avoid predators, echidnas dig and burrow to hide and leave their spines exposed to discourage an attack. Echidna spines work well for protection, but if a predator is able to flip them over to reveal their soft belly, they are left vulnerable prey.

The larger size of long-beaked echidnas makes them less susceptible to natural predators. If they do have any, instances have not been observed often as long-beaked echidnas live a secretive life. The biggest threat they face is humans, both from hunting and habitat loss.

Ecosystem Roles

Short-beaked echidna burrowing habits have positive effects on soil microbiota. Echidna foraging pits have more enzymatic and microbial activity than the surface and subsoil. The pits they dig have more effective microbial communities and thus are important to nutrient cycling in the soil.

• Ecosystem Impact
• soil aeration soil aeration

Economic Importance for Humans: Positive

Echidnas are a charismatic species endemic to Australia and provide opportunities for ecotourism. Long-beaked echidnas are an important food source for natives.

• Positive Impacts
• food food
• ecotourism ecotourism

Economic Importance for Humans: Negative

There are no known adverse effects of echidnas on humans.

Conservation Status

Short-beaked echidnas are listed as least concern on the IUCN's red list, but is considered endangered under the Commonwealth of Australia. Long-beaked echidnas are listed as Appendices II under CITES and critically endangered on the IUCN except for eastern long-beaked echidnas, which are listed as vulnerable. Long-beaked echidnas are at risk due to humans hunting them for food as well as habitat loss from the logging industry.

Additional Links

Encyclopedia of Life

Contributors

Neilee Wilhelm (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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