Animal Diversity Web

Ge­o­graphic Range

An­tech­i­nus swain­sonii is found in south-east­ern Aus­tralia, rang­ing from south­ern Queens­land to east­ern South Aus­tralia, through­out Vic­to­ria and New South Wales, and on the is­land of Tas­ma­nia. (Williams and Williams, 1982)

• Biogeographic Regions
• australian
  • native

Habi­tat

A. swain­sonii are most com­monly found in the moist scle­ro­phyll forests and rain­forests of the Aus­tralian main­land and Tas­ma­nia. A. swain­sonii have also been found to in­habit fields over­grown with high grasses but favor any habi­tat with a dense un­der­story, where most of their ac­tiv­i­ties are re­stricted (Williams and Williams 1982).

• Habitat Regions
• tropical

• Terrestrial Biomes
• forest
• rainforest

Phys­i­cal De­scrip­tion

A. swain­sonii range in color from dark gray to black. Males and fe­males are sex­u­ally di­mor­phic with an av­er­age weight of 65 grams for males, and 41 grams for fe­males (Tas­ma­nia PWS 2001; Mam­mals of Lam­ing­ton Na­tional Park 2001). Males have been re­ported to reach 130 grams and fe­males 70 grams and it is be­lieved that weight is vari­able due to avail­abil­ity of re­sources (Williams and Williams 1982). The av­er­age head and body length of A. swain­sonii is 128mm and the av­er­age tail length is 116mm (Mam­mals of Lam­ing­ton Na­tional Park 2001).

• Other Physical Features
• endothermic
• bilateral symmetry

• Average mass

  41 g

  1.44 oz

  AnAge

• Average basal metabolic rate

  0.351 W

  AnAge

Re­pro­duc­tion

Com­pe­ti­tion for mates is ex­tremely high among males. Dur­ing mat­ing, males have been ob­served to grab the scruff of the fe­males neck with their teeth, while the fe­males re­spond by kick­ing, rolling, and a dis­play of open-mouthed hiss­ing (Williams and Williams 1982). Dur­ing the breed­ing sea­son males do not eat, but their body is sus­tained through glu­co­neogenic mo­bi­liza­tion of body pro­tein (Nowak 2001). This re­sults in de­te­ri­o­ra­tion of the male's im­mune sys­tem and death usu­ally within three weeks of cop­u­la­tion. These vic­tims of male "die-off" have been found to have bald­ing patches lo­cated on their fur (Tas­man­ian PWS 2001).

Fe­males breed once, some­time be­tween May and Sep­tem­ber, and there is con­sid­er­able ev­i­dence that the tim­ing of breed­ing is cor­re­lated with en­vi­ron­men­tal con­di­tions (Williams and Williams 1982). Pop­u­la­tions in coastal re­gions and at lower al­ti­tudes have ear­lier breed­ing sea­sons than in­land or higher-el­e­va­tion pop­u­la­tions, and pop­u­la­tions on the main­land breed ear­lier than those on Tas­ma­nia. Avail­abil­ity of food, tem­per­a­ture, al­ti­tude and cli­mate may all play a role in the tim­ing of a pop­u­la­tion's breed­ing sea­son.

Ges­ta­tion lasts 29-36 days. In cap­tiv­ity fe­males show vis­i­ble signs of en­larged nip­ples 19 days after cop­u­la­tion; an en­larged, but con­cealed, pouch at 21 days; and by 23 days, a pouch that is di­vided into two halves by a ridge (Williams and Williams 1982). The pouch only be­comes vis­i­ble a few days be­fore birth.

A birthing fe­male places her­self on all fours with her hindquar­ters up slightly as the young emerge. A. swain­sonii pro­duce su­per­nu­mery off­spring (more off­spring than avail­able teats), and some off­spring do not reach an avail­able teat, re­sult­ing in their death (Williams and Williams 1982).

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

• Breeding season

  May-September

• Range number of offspring

  6 to 8

• Average number of offspring

  8

  AnAge

• Range gestation period

  29 to 36 days

• Average weaning age

  14 weeks

• Average age at sexual or reproductive maturity (female)

  8 months

• Average age at sexual or reproductive maturity (female)
  Sex: female

  330 days

  AnAge

• Average age at sexual or reproductive maturity (male)

  8 months

Young av­er­age 4.5mm in length at birth with well de­vel­oped claws on their fore­limbs, and a large cir­cu­lar mouth (Williams and Williams 1982). A sex­u­ally ma­ture fe­male has eight teats and lit­ter size ranges from 6-8 young (Nowack 2001). The young are bright pink at birth, but begin to de­velop fur at 8 weeks with their eyes open­ing shortly after. The young are left alone in the nest at 10 weeks and begin to eat solid food at 12 weeks. By the 14th week the young are com­pletely weaned and travel out­side of the nest at­tached to their moth­ers back (Williams and Williams 1982). A. swain­sonii de­velop slowly and are fully ma­ture around 8 months, near the be­gin­ning of the next breed­ing sea­son.

• Parental Investment
• altricial
• female parental care

Lifes­pan/Longevity

Fe­males of the species A. swain­sonii usu­ally die after rear­ing their first lit­ter and males die shortly after cop­u­la­tion (Williams and Williams 1982). Males cap­tured after breed­ing sea­son still die within the same time pe­riod as wild males from their pop­u­la­tion, but males cap­tured be­fore the breed­ing sea­son have lived up to two years and eight months (Nowak 2001). Fe­males can live over two years, pro­duc­ing a 2nd lit­ter, but as stated above most die after rear­ing one lit­ter.

• Range lifespan
  Status: captivity

  3 (high) years

• Average lifespan
  Status: captivity

  3.3 years

  AnAge

Be­hav­ior

A. swain­sonii are noc­tur­nal. In cap­tiv­ity how­ever, in­di­vid­u­als were ob­served to be ac­tive day and night with pe­ri­ods of ex­tended pe­ri­ods of rest around 12 p.m. and 6 a.m. (Williams and Williams 1982). Fully de­vel­oped adults are soli­tary with so­cial in­ter­ac­tions oc­cur­ring dur­ing mat­ing and be­tween mother and young. A. swain­sonii spend most of their ac­tive pe­riod feed­ing, as some in­di­vid­u­als have been es­ti­mated to eat about 60% of their body weight dur­ing the win­ter months (Nowak 2001). Mem­bers of the species seem to have a def­i­nite home range, but are not ter­ri­to­r­ial. A. swain­sonii con­struct nests from eu­ca­lypt leaves that are balled up in hol­low tree trunks or in the dense un­der­story of the for­est floor (Tas­ma­nia PWS 2001). There is a low mor­tal­ity rate among young as con­sid­er­able time and ef­fort is in­vested ma­ter­nally in rear­ing lit­ters (Williams and Williams 2001).

• Key Behaviors
• nocturnal
• motile
• solitary

Com­mu­ni­ca­tion and Per­cep­tion

• Perception Channels
• tactile
• chemical

Food Habits

A. swain­sonii feed mostly on soil in­ver­te­brates, as their pri­mary habi­tat is the for­est floor. Along with worms and in­sects they have been ob­served eat­ing lizards, small birds, fruit and veg­e­ta­tion (Tas­man­ian PWS 2001. Mam­mals of Lam­ming­ton Na­tional Park 2001.) In cap­tiv­ity in­di­vid­u­als have been sus­tained on earth­worms, meal­worms, grasshop­pers, bee­tle lar­vae, cock­roaches, and small frozen mice. (Williams and Williams 1982)

• Primary Diet
• carnivore
  • insectivore

• Animal Foods
• birds
• mammals
• amphibians
• insects
• terrestrial worms

• Plant Foods
• leaves
• fruit

Pre­da­tion

Do­mes­tic cats are the only se­ri­ous threat of pre­da­tion to A. swain­sonii. (Nowak 2001)

Ecosys­tem Roles

In their niche on the for­est floor, A. swain­sonii help con­trol the pop­u­la­tion of soil in­ver­te­brates with their vo­ra­cious ap­petites.

Con­ser­va­tion Sta­tus

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Migratory Bird Act

  No special status

• US Federal List

  No special status

• CITES

  No special status

Con­trib­u­tors

Je­remy Bates (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, On­drej Pod­laha (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Oc­to­ber 20th, 1997. "Tas­ma­nia Parks and Wildlife Ser­vice" (On-line). Ac­cessed Oc­to­ber 7th, 2001 at http://​www.​parks.​tas.​gov.​au.

Collins, L. 1973. Monotremes and Mar­su­pi­als. Wash­ing­ton D.C.: Smith­son­ian In­sti­tu­tion Press.

Nowak, R. 1995. "Walker's Mam­mals of the World On­line - The John Hop­kins Uni­ver­sity Press" (On-line). Ac­cessed Oc­to­ber 7th, 2001 at http://​www.​press.​jhu.​edu/​books/​walker/​.

Uni­ver­sity of Queens­land, S. March 21st, 2000. "Lam­ing­ton Na­tional Park Web­site" (On-line). Ac­cessed Oc­to­ber 7th, 2001 at http://​lamington.​nrsm.​uq.​edu.​au.

Williams, A., R. Williams. 1982. The Life Cycle of An­tech­i­nus Swain­sonii. Car­niv­o­rous Mar­su­pi­als Vol­ume 1. New South Wales, Aus­tralia: Royal Zo­o­log­i­cal So­ci­ety of New South Wales.