Antechinus argentus, Baker, Mutton & Hines, 2013

Russell A. Mittermeier & Don E. Wilson, 2015, Dasyuridae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 232-348 : 309-310

28.

Silver-headed Antechinus

Antechinus argentus

French: Antéchinus a téte argentée / German: Silberfarbene BreitfulRbeutelmaus / Spanish: Antequino de cabeza plateada

Taxonomy. Antechinus argentus Baker, Mutton & Hines, 2013 ,

Kroombit Tops National Park , about 400 km NNW of Brisbane and 60 km SSW of Gladstone, southeastern Queensland, Australia.

The first A. argentus was captured in 1992 by L. Hogan from Queensland Forestry; the specimen eventually made its way to the Queensland Museum where it was identified as A. flavipes . In 2011, the taxonomy of A. flavipes was revised, leading to the discovery of A. mysticus to which the 1992 Kroombit specimen was assigned. Fresh specimens were subsequently collected from Kroombit Tops that looked strikingly different from A. mysticus and the 1992 Kroombit specimen; it eventually became clear that the earlier Kroombit specimen had been victim to an uncertain preservation history, bleaching and washing out its color. After several additional collecting trips to Kroombit Tops, A. argentus was formally described. Phylogenetically, it is most likely sister to A. mysticus ; the two species are clearly genetically divergent (7-2-7-5% different in mtDNA). Monotypic.

Distribution. E Australia (SE Queensland), apparently limited to the escarpment at Kroombit Tops National Park, 400 km NW of Brisbane and 60 km SW of Gladstone.

Descriptive notes. Head-body 9.4-10.7 cm (males) and 8.1-8.8 cm (females), tail 8.7-10.8 cm (males) and 7.8-8.5 cm (females); weight 28-9-38-1 g (males) and 18-23 ¢ (females). There is marked sexual dimorphism in size. The Silver-headed Antechinus can be easily distinguished in the field, having an overall silver appearance, with much paler silver feet and tail base and drabber, deep-grayish-olive rump than the Yellowfooted Antechinus ( A. flavipes ), which has yellow-orange toned feet, rump, and tail base. The Silver-headed Antechinus possesses a striking silver-gray head and neck with prominent pale, slightly broken eye rings, and this distinguishes it from the Buff-footed Antechinus ( A. mysticus ), which has a more subtle grayish-brown head and neck, pale brown dabs of eyeliner, and more colorful brownish-yellow rump.

Habitat. Gently undulating plateau at elevations of ¢.850-900 m (type locality). The plateau is bounded to the east by a steep escarpment, dominated by a cliff line up to c.50 m in height. Habitat on this part of the plateau is a Eucalyptus montivaga shrubby tall open-forest with occasional Corymbia intermedia (both Myrtaceae ). In places, there is a lower tree layer of Allocasuarina (Casuarinaceae) . Shrub layer varies considerably in height, cover, and species, including Acacia (Fabaceae) , Leptospermum (Myrtaceae) , Leucopogon (Ericaceae) , Lophostemon confertus (Myrtaceae) , Persoonia (Proteaceae) , Seringia arborescens ( Sterculiaceae ), and Xanthorrhoea ( Xanthorrhoeaceae ). There is a sparse to moderately dense ground cover of grasses (including Imperata cylindrica Poaceae ), ferns (including Blechnum cartilagineum, Calochlaena dubia , and Pteridium esculentum), and herbs such as Goodenia (Goodeniaceae) . Large, hollow-bearing trees (especially E. montivaga) and large, fallen woody debris are common. There is no outcropping rock, except at the top of the cliff line. Soil is a pale, sandy loam of low-tomoderate fertility, derived from Precipice Sandstone.

Food and Feeding. There is no specific information for this species, but dietary habits of the Silver-headed Antechinus and research investigating fecal pellet components of individuals at Kroombit Tops are currently underway.

Breeding. Little is known of breeding biology of the Silver-headed Antechinus, but some descriptive notes are worth mentioning. In a field study, several adults were captured in March 2013, and upper third premolar had barely descended, which is the mark of adulthood, so presumably these individuals were c.7-8 months of age. If true, this would place the several individuals caught later that year in mid-June at c¢.10-11 months of age. One female Silver-headed Antechinus caught at this time had a furry, non-discolored pouch area, indicating that she was not pregnant, and nipples were not distinguishable either by eye or microscope. On 26 August 2013, three females were caught from 400 trap nights, 4 km from the type locality, each with eight young measuring 0.8-0.9 cm crown-rump length. Based on neonatal growth in the similarsized Brown Antechinus ( A. stuartii ), one might assume this equates to c.2-3week-old young. If so, assuming c.30 days of gestation (which has been recorded in Yellow-footed Antechinus ), this would mean young were born in the first or second week of August and females became pregnant in the first or second week of July. Thus, mating season of Silver-headed Antechinus should occur from late June to late July; male die-off, characteristic of species of antechinuses, presumably coincides with a 1-3 week mating period occurring within this date range. By comparison,field studies and museum records have shown that the Buff-footed Antechinus in south-eastern and mid-eastern Queensland apparently breed about one month later, sometime between late July and late August each year.

Activity patterns. Silver-headed Antechinuses are presumably predominantly nocturnal. One individual was seen emerging from a vertical tree trunk hollow at dusk in March 2013; upon approach, it became wary and ducked back into a nearby hollow on the same tree. No other details of activity are known for this species.

Movements, Home range and Social organization. In one field survey, a male Silverheaded Antechinus was caught along the same Elliot trap line on successive nights in traps less than 100 m apart. No other information about movement or social organization is known, but research is currently underway for the Kroombit population.

Status and Conservation. The Silver-headed Antechinus has not been classified on The IUCN Red List, however, a current Australian proposal recommends thatit be listed in Queensland as vulnerable. To date, the Silver-headed Antechinus has only been found across ¢.10 km?; if this is even close to its true distribution, then it possesses one of the smallest known distributions of any Australian mammal. It is noteworthy that after more than 5500 trap nights in the last few years at Kroombit Tops and nearby national parks, with a focus on the Lookout area at Kroombit, only 13 antechinuses have been caught: one male Yellow-footed Antechinus and twelve Silver-headed Antechinuses (seven males and five females). Only one antechinus for every 350 traps (or one for every 150 traps near the type locality) is a very low capture rate compared to an average capture rate of about one for every 25-50 traps for Yellow-footed Antechinuses and Bufffooted Antechinuses in surrounding locales of south-eastern Queensland. Low catch rate of Silverheaded Antechinus is even more profound when one considers that no rodents in the genus Rattus have been caught at Kroombit Tops—when Elliott-trapping is undertaken in south-eastern Queensland, Rattus spp. (typically the Australian Bush Rat, Rattus fuscipes ) often fill one-half of the laid traps (and up to one every three traps). Given the absence of Rattus spp., up to two in every three traps have been successful in catching antechinus at Kroombit Tops, more than from an equal trapping effort anywhere else. Taken together, the very low trapping success rate, the apparently very limited distribution, and the other endemic vertebrate fauna found within Kroombit suggests that the Silver-headed Antechinus may even warrant a federallisting of endangered. Much will be learned from detailed surveys of Kroombit and its surroundings in the coming years. There are a variety of threats within the national park, including domestic cattle, feral pigs, feral horses, frequent controlled burning, and bushfires. If the Silver-headed Antechinus is indeed limited to the national park, its future could be at considerable risk.

Bibliography. Baker et al. (2013), Marlow (1961), McAllan (2003), Queensland Herbarium (2013), Smith, G.C. (1984), Willmott (2006), Woolley (1966).

Figures

On following pages: 2. Crest-tailed Mulgara (Dasycercus cristicauda); 3. Kowari (Dasyuroides byrnei); 4. Kaluta (Dasykaluta rosamondae); 5. Dibbler (Parantechinus apicalis); 6. Woolley's Three-striped Dasyure (Myoictis leucura); 7. Miller's Three-striped Dasyure (Myoictis melas); 8. Wallace's Three-striped Dasyure (Myoictis wallacii); 9. Tate's Three-striped Dasyure (Myoictis wavicus); 10. Sandstone Pseudantechinus (Pseudantechinus bilarni); 11. Fat-tailed Pseudantechinus (Pseudantechinus macdonnellensis); 12. Carpentarian Pseudantechinus (Pseudantechinus mimulus); 13. Ningbing Pseudantechinus (Pseudantechinus ningbing); 14. Rory’s Pseudantechinus (Pseudantechinus roryi); 15. Woolley's Pseudantechinus (Pseudantechinus woolleyae); 16. Speckled Dasyure (Neophascogale lorentzii); 17. Red-bellied Phascogale (Phascolosorex doriae); 18. Narrow-striped Dasyure (Phascolosorex dorsalis).

Distribution. E Australia (SE Queensland), apparently limited to the escarpment at Kroombit Tops National Park, 400 km NW of Brisbane and 60 km SW of Gladstone.