Short-beaked Echidna (Tachyglossus aculeatus) Fact Sheet: Reproduction & Development

Finding a mate

• After hibernation, emerging males compete for emerging females (Morrow and Nicol 2009; Nicol 2015a)
  • Intense competition among males in some locations (e.g., Kangaroo Island and Tasmania) (Morrow et al. 2009)
  • Mating often occurs soon after emergence from hibernation: 1-3 weeks, depending on latitude and elevation (Morrow et al. 2009)
• Males search large areas for females, possibly by following odor of females(Augee et al. 2006; Nicol 2015b)
• Males may seek out and mate with hibernating/torpid females (Morrow et al. 2009; Morrow and Nicol 2009)
  • Occurs in some locations (e.g.,Tasmania), likely due to extreme competition among males
  • Females may re-enter a deep torpor after mating
  • Gestation begins after waking from hibernation
    • Also see “Pregnancy” in Gestation and Birth

Mating system

• Polygamous and promiscuous
  • Males and females typically copulate with more than one mate (e.g., Morrow and Nicol 2009)
  • Mating system dynamics are not well understood in more remote regions or areas of low echidna density (Nicol 2015a)
  • Males “guard” females before and after mating (Morrow and Nicol 2009)
• Where population densities are high, intense competition exists among males
  • Evidence of competition: (Nicol 2015a; Morrow et al. 2016)
    • Large testes in males
    • Reproductive behaviors that occur over a long period of time
  • Not all males breed each year (Morrow et al. 2009)

Courtship habitats

• Courtship groups observed in a variety of habitats (Morrow et al. 2009):
  • Under rocks or rocky overhangs
  • Grass tussocks
  • Hollows at the base of trees
  • Rotten tree stumps
  • Hollow logs
  • In burrows and depressions in the soil

Group size

• Depends on geographic location (Morrow and Nicol 2009)
  • Ranges from a male-female pair to an “echidna train” (see below) of more than 10 individuals (Augee et al. 2006)
    • In Tasmania, most commonly one male to one female (SC Nicol, personal communication, 2017)
      • Up to four males to one female
    • On Mount Kosciuszko, only one male and one female observed together (Nicol 2015a)

Courtship: “echidna train” behavior

• “Echidna train”: when one male or a group of males follow a female, single-file; typically four males or fewer, but up to 11 (Nicol 2015a)
  • Female in front; males follow behind, single-file
  • Males jostle the female and each other, competing for access to the female
• This behavior is only observed in some locations, such as Kangaroo Island and central and southeastern Australia; it is not representative of all populations (Rismiller and McKelvey 2000; Morrow et al. 2009)
  • Unknown why echidna train behavior does not occur in some locations (e.g., Snowy Mountains); may be influenced by population density
• Kangaroo Island population
  • Pursuit of females can last 14-44 days, but the composition of male followers changes (Nicol 2015a)
    • Males typically stay with a group up to a week (Morrow et al. 2009)
• Mating aggregations have a musky smell, likely caused by sulphur compounds found in their gland secretions (Harris et al. 2012 citing Nicol et al. 2004)

Signaling and copulation

(descriptions from Nicol 2015a, and as noted)

• Female behavior
  • On Kangaroo Island, a receptive female responds by lying flat on the ground with her spines relaxed
  • If not receptive, the female will curl up into a spiky ball to keep males away (Augee et al. 2006)
• Male behavior
  • The male probes the female with his snout, paws her flank and tail, and/or sniffs along her back (Augee et al. 2006)
  • If one male is present, he digs on one side of the female, stroking her spines with his front foot and attempting to lift her tail with his hindfoot
    • Male digs in order to adopt a cloaca-to-cloaca position
    • May or may not adopt a sitting position
  • If several males are present, they all attempt to dig beside the female, while trying to push other males away
• Copulation is prolonged: 30-180 min
  • May be a means of excluding rival males (Johnston et al. 2007)
• The pair then separates (Augee et al. 2006)
  • Within a couple of days, the female again becomes solitary
  • The male pursues other mating opportunities or returns to his home range

General

• Sexual maturity
  • Minimum age in the wild (Nicol et al. 2018)
    • On Kangaroo Island, at about 5 years of age
    • May vary geographically and/or by population
    • Rismiller and McKelvey (2003) report that reproductive behavior begins between 5 and 12 years of age
  • Minimum age in managed care (Wallage et al. 2015; Nicol et al. 2018; Andrea Wallage, personal communication, 2017, unreferenced)
    • May reach maturity earlier in managed care than in the wild—at about 3 years of age
• Timing and length of reproductive stages
  • Time from attracting males to weaning of young is long: 7-9 months in Australia (Rismiller and McKelvey 2009)
  • Gestation is short: about 21-22 days (Morrow et al. 2009; Nicol 2015a)
  • Time from fertilization to weaning is very long: 170-240 days (Nicol 2015a)
• Reproductive organs and structures
  • Males (Johnston et al. 2007; Nicol 2015a, and as noted)
    • Penis is unusually shaped
      • Deep groove at the tip creates ‘two halves’ (bilaterally symmetrical); elaborate, rosette-like head structure
      • Structure is unlike that of any other mammal; reminiscent of the penis of lizards and snakes
    • Penis is only used for passage of sperm; urine is eliminated via the cloaca
    • When not erect, the penis is inverted and held in a sac within the cloaca; protrudes through the cloaca when erect (Augee et al. 2006)
    • Sperm production is seasonal (Augee et al. 2006)
      • Testes greatly increase in size prior to hibernation (February-May, depending on the population) and shrink after the mating season ends in September (Morrow et al. 2016)
        • Echidnas are the only mammal in which this ‘testes renewal process’ occurs prior to hibernation
        • Allows males to maximize hibernation time and mate shortly after hibernation
    • Large sperm bundles aid sperm motility; likely aids sperm competition
  • Females
    • Eggshell formation first occurs in the oviduct, then the uterus (Augee et al. 2006)
    • Pouch develops during the breeding season (Nicol 2015a)
    • No nipples/teats; have two lateral areolae that produce milk, surrounded by hairs for the young to hold onto (Nicol 2015a)

Breeding

• Echidnas breed annually (Rismiller and McKelvey 2000) and seasonally (Nicol 2015b)
  • Timing varies with latitude; begins slightly later in more northerly populations
  • Breeding timed so that young are weaned when food is abundant (Morrow and Nicol 2012)
• Mating periods may be long: up to two months (Morrow et al. 2009)
• Reproductive activity
  • Begins mid-winter, shortly after waking from hibernation (Nicol and Andersen 2007b)
  • Non-reproductively active echidnas in cold (eastern) areas of Australia normally hibernate through to spring (Morrow et al. 2009)
• Timing of mating (Rismiller and McKelvey 2009; Nicol 2015b, except as noted)
  • Little variation among latitudes/populations; breed during winter, with some regional variation (Nicol and Andersen 2007b; Morrow et al. 2009)
    • Southeastern Queensland: mid-July–early September
    • Tasmania: early June–September
    • Kangaroo Island: early June–early August
    • Mount Kosciuszko: late June–early August
  • In colder areas, mating follows a period of hibernation (Beard et al. 1992; Nicol and Andersen 2002)
  • In Queensland and Tasmania, a second mating may occur in October if first young dies
• Number of young
  • Females usually conceive once in a season but may do so a second time if the first young dies; uncommon (Augee et al. 2006; Harris and Nicol 2014)
    • Cases of twins very rare
      • See Pierce et al. (2007)

Pregnancy

• Females develop a pouch during late pregnancy (Nicol 2015a)
  • Pouch and mammary glands shrink as young reach independence and mothers stop lactating (Morrow and Nicol 2012)
• Females are often harassed by males, even during gestation (Morrow and Nicol 2012)
• Little known about the behavior of female echidnas during the early weeks of gestation (Augee et al. 2006)
  • In some locations, females dig a nursery burrow (see below) or use an existing burrow dug by another animal, plugging entrance with soil (Nicol 2015a)
    • Dig the burrow 1-2 days before egg-laying (Morrow et al. 2009)
    • Female will remain in the burrow until young are about six weeks old
  • In other locations, females use shelter sites with natural openings, such as under tree roots, rock crevices, etc. (Rismiller and McKelvey 2000)
  • Females in some locations re-enter hibernation after mating; typically within the first few days of pregnancy (Morrow and Nicol 2009; Morrow and Nicol 2012; Morrow et al. 2017)
    • No significant embryo development appears to occur during hibernation; similar to embryonic diapause in marsupials (Morrow et al. 2017)
      • Embryonic growth slowed until environmental conditions are better for milk production and survival of young
    • Other than bats, echidnas are the only other mammals known to hibernate while pregnant
• Egg-laying is infrequently observed (Augee et al. 2006)
  • In Tasmania, occurs July-October (Morrow et al. 2009)
• Gestation period: about 21-22 days (Morrow et al. 2009; Nicol 2015a); longer for hibernating females (e.g., in Tasmania; 22-48 days) (Rismiller and McKelvey 2000; Nicol and Morrow 2012)
• Usually produce one young
  • Cases of twins very rare

Egg incubation and hatching

• Produce one soft, leathery egg; outer shell layers are not mineralized (Rismiller and McKelvey 2003; Augee et al. 2006; Nicol 2015a)
  • Shape: round or slightly oval
  • Size: 13-17 mm (0.5-0.7 in); about the size of a grape
  • Weight: 0.3-2.0 g (0.05-0.07 oz)
• Egg laid via the cloaca (Augee et al. 2006)
• Female moves the egg from the cloaca to the pouch, where it is incubated for 10-11 days before it hatches (Morrow and Nicol 2012; Nicol 2015a)
  • Most development of the embryo and its organs occurs during this period, in contrast to other mammals (except the platypus)
• Hatchling uses its egg tooth to cut open the egg; this tooth disappears after hatching (Augee et al. 2006)
• Description of hatchling
  • No hair (Nicol 2015a)
  • No pigments on skin (Morrow and Nicol 2012); body is semi-translucent (Augee et al. 2006)
  • Size at hatching: 13-15 mm (0.51-0.59 oz) (Nicol 2015a)
  • Weight at hatching: about 0.3 g (0.1 oz) (Nicol and Andersen 2007b)
  • Front legs and claws are well developed compared to hind limbs; help hatchling cling to pouch hairs (Nicol 2015a)
  • Eyes and hind legs are undeveloped (Nicol 2015a)
    • May use smell to find a milk patch (Augee et al. 2006)
• After hatching, young is carried in its mother’s pouch (Morrow et al. 2009)
  • Suckles continuously until evicted from the pouch

Maternal investment

• Females exhibit a variety of complex care behaviors (Morrow and Nicol 2012)
  • Males do not assist with rearing young (Nicol 2015b)
• Patterns of maternal care vary by geographic location; climate appears to be more of an influence than physiology (Morrow et al. 2009)
  • Mild climates: female may forage with egg in pouch 45-50 days after hathcing, then dig nursery burrow and leave young there (Rismiller and McKelvey 2009; Nicol 2015a)
  • Cool climates: female stays in nursery burrow for 4-6 weeks, then leaves young in nursery burrow to forage (Morrow et al. 2009; Rismiller and McKelvey 2009, citing studies by Beard et al.; Morrow and Nicol 2012)
  • Intermediate climates: female stays in nursery burrow 2-3 weeks, then forages with young in pouch until young 40-45 days old, then leaves young in different nursery burrow until weaning (Morrow et al. 2009)
• As the lactation period progresses, mother forages in larger areas for longer periods of time (Augee et al. 2006; Morrow et al. 2009; Rismiller and McKelvey 2009)
  • Not in Tasmania
  • Returns every 5-10 days to nurse young, staying only a few hours at a time

Nursery burrows

(Morrow and Nicol 2012; Nicol 2015a, and as noted)

• Specifically built for reproduction; daily shelter sites are not used as nursery burrows (Rismiller and McKelvey 2009)
  • Burrow from previous breeding seasons are almost never reused
• Location of nursery burrows (Augee et al. 2006; Rismiller and McKelvey 2009)
  • Varies by geography, but includes piles of soil, leaf litter, termite mounds, near tree roots, rocks/caves, sand hills, or open ground (e.g., pasture or dry sclerophyll)
  • Mothers may move their burrow location (e.g., if seeking better burrow temperatures or lose young to predators)
• Characteristics of nursery burrows
  • Shallow depth
  • Single entrance, back-filled with dirt to prevent access by predators and to stabilize the burrow’s temperature; mothers re-plug entrance when exiting to forage and young are left on their own
  • Some have multiple chambers
  • No lining/nesting material (e.g., no leaves, sticks)
• The importance of temperature
  • When mothers remain in burrow
    • Mothers’ body heat keeps burrow temperature stable and warm—at least 7°C (44°F) above soil temperatures
      • Essential for early development of young
    • Females lose body weight as they expend energy to warm the burrow, but do not forage
  • When females leave to forage (Morrow and Nicol 2012)
    • If younger than 100 days old, young usually become hypothermic when alone in nursery burrow; may enter torpor if their body temperature falls too low while their mothers are away
    • After 100 days, young have developed thick fur and are better able to maintain their body temperature

Nourishment of young and female foraging

• Mother echidnas produce milk for their young, like live-bearing mammals (Nicol 2015a)
• No nipples/teats; young nurse from two milk patches (areolae) located at the center of the pouch (Nicol 2015a)
• Fat and protein content in the milk increases during the lactation period (Augee et al. 2006; Nicol 2015a)
  • Fat: 1.25% to 31%
  • Protein: 7.8% to 12.4%
    • May be related to demands for keratin in growing hair and spines in young animals
• Lactation period: varies geographically and among subspecies (Nicol 2015a)
  • Geographically
    • Tasmania: 125-145 days
    • Southeastern Queensland: 150-165 days
    • Kangaroo Island and Western Australia: 200-210 days
  • Among subspecies
    • T. a. aculeatus: not reported
    • T. a. acanthion and T. a. multiaculeatus: 200-210 days
    • T. a. lawesii: not reported
    • T. a. setosus: up to 147 days
• Weaning
  • See “Newborns” in Life Stages, below

Newborns

• Often called “puggles” (Rismiller and McKelvey 2000; Nicol 2015a)
• Substantial differences among subspecies in growth and development of young, and maternal behavior (SC Nicol, personal communication, 2017)
• Important physical developments (Morrow and Nicol 2012)
  • Hair becomes dense
  • Spines and limb fully develop
  • Young gain ability to regulate body temperature
• Rapid growth during first 60 days (Augee et al. 2006)
• Weaning
  • Gradual, at least in some populations (Morrow and Nicol 2012)
  • Variable among populations; range: 140-210 days (Rismiller and McKelvey 2000; Augee et al. 2006; Morrow and Nicol 2012; also see Discussion of Rismiller and McKelvy 2009)
    • Snowy Mountains: ~ 210 days
    • Kangaroo Island: 204-210 days
    • Western Australia: 195-200 days
    • SE Queensland and Tasmania: occurs much earlier 140-160 days
  • After weaning, mothers do not return to the nursery burrow (Morrow and Nicol 2012)
• See Parental Care, above

Juveniles

• Remain in their mothers’ home ranges their first year, before dispersing at about 12-18 months of age (Rismiller and McKelvey 2000; Morrow and Nicol 2012; Nicol 2015a)
  • Not certain whether males disperse farther than females

Adults

• Reach adult body weight after about 3-6 years (Nicol and Andersen 2007b)

Wild populations

• Lunn et al. (2022) found an average life span of 16.7 years (in years with good rainfall and milder temperatures; life span was much shorter during periods of low rainfall and harsh temperatures)
  • More males survive than females (Nicol et al. 2019)
• Some echidnas are exceptionally long-lived (Rismiller 1999; Nicol 2015a)
  • Can live four times longer than expected for their body size (Hulbert et al. 2010)
  • Probably can be attributed to a combination of factors:
    • Adaptations for conserving energy (e.g., low metabolic rate, torpor and hibernation) (Nowack et al. 2016)
    • Fatty acid composition of their cell membranes (see Hulbert et al. 2010)

Managed care

• Median life expectancy
  • No AZA estimates
• Also see “Victor the Echidna” in History of Managed Care

Survival rates

• Morrow and Nicol (2012) report that high mortality of young occurs during the period when mothers remain within their nursery burrows (the first two weeks of lactation)
  • Cause of death unknown, but may be related to temperature conditions
• Rismiller and McKelvy (2000) report that, on Kangaroo Island, only 8 of 22 young that hatched survived to weaning
  • The authors estimated that a female echidna may only produce one young every 4 to 6 years, despite an annual breeding cycle
• Other critical life periods may include the first few months after weaning and during dispersal (Nicol and Andersen 2007b)

Predators

(Augee et al. 2006; Rismiller and McKelvey 2009; Nicol 2015a, and as noted)

• Burrow young are most susceptible to predation (Nicol and Andersen 2007b); adults are well protected by their spines
• Predators of young and juvenile echidnas
  • Large lizards (e.g., monitor lizards, Varanus)
  • Snakes
  • Feral cats, Felis catus
  • Foxes
  • Pigs
• Predators of adult echidnas
  • Dingoes, Canis lupus dingo
  • Tasmanian devils, Sarcophilus harrisii (Morrow and Nicol 2012)
  • Humans
  • Possibly domestic dogs (Canis lupus familiaris) and foxes; it is not clear if spines found in gut contents of these animals is from scavenging or active hunting
• Predators of the past (Nicol and Andersen 2007b)
  • Large, carnivorous marsupials
  • Large reptiles
  • Thylacines
  • Tasmanian devils
  • Quolls

Accidental death

• Hit by motor vehicles (Nicol 2015c)
  • Very common

Diseases (non-comprehensive list) (Beard et al. 1992)

• Viral infections, pox and ones similar to herpes

Parasites (non-comprehensive list)

• Flatworms (Beard et al. 1992)
• Tapeworms (Augee et al. 2006)
• Protozoal infections (Beard et al. 1992)
• Fleas (Beard et al. 1992)
• Ticks (Augee et al. 2006)
• Mites (Beard et al. 1992)

"When we look at the details of echidna biology, we are not looking at a 'living fossil' that has failed to join modern mammals such as ourselves in the 'fast lane', but [rather, the echidna has] found a niche in the 'slow lane' that is so successful that it has remained there for millions of years."

— Augee et al. 2006, Echidna: Extraordinary Egg-laying Mammal