Rock-Haunting Ringtail Possum (Petropseudes dahli) of Groote Eylandt and Northern Australia

Rock-loving ringtail possums answer to the common names of:

• Australian rock ringtail;
• Rock ringtail possum;
• Rock-haunting ringtail possum.  

They carry the binomial name Petropseudes dahli within the taxonomic system of Greek- and Latin-inspired nomenclature. The genus name Petropseudes combines the Greek words πέτρα (pétra, “rock”) and ψευδής (pseudēs, “false”). It honors the decision by Millbrook-born British mammalogist Michael Rogers Oldfield Thomas (February 21, 1858 – June 16, 1929) in 1923 to replace the original name Pseudochirus -- from the Greek words ψευδής and χειρό- (cheiró-, “hand”) -- selected in 1895 by Norwegian zoologist Robert Collett (December 2, 1842 – January 27, 1913). Spelled Pseudocheirus, the original genus name persists as the designation for common (peregrinus) and western (occidentalis) ringtails.

The species name dahli continues unchanged since Robert Collett’s official description and designation of rock ringtails in 1895. It designates the zoological achievements of Hakadal-born Norwegian explorer and scientist Knut Dahl (October 28, 1871 – June 11, 1951) in the Northern Territory and Western Australia. It honors Robert’s decision to memorialize Knut’s commitment with taxidermist Ingel Holm to:

• Collecting animal specimens for the University of Oslo’s Zoological Museum curated by Robert since 1864;
• Identifying birds -- Banded Fruit-doves (Ptilinopus cinctus alligator), Chestnut-quilled Rock-Pigeons (Petrophassa rufipennis), and Hooded Parrots (Psephotus dissimilis) -- unknown to European audiences until the publication of official descriptions by Robert in 1898 as ZSL foreign member-elect in the Proceedings of the Zoological Society of London. 

Mary River’s granite boulder-riddled upper reaches and Arnhem Land’s granite- and sandstone-surrounded South Alligator River in the Northern Territory act as respective memorials to pioneer retrievals of 3 specimens by Knut in 1895 and of 24 by Kojonup-born Australian naturalist John Thomas Tunney (October 11, 1871 – June 10, 1929) in 1903 – 1904. The Northern Territory’s uplands indeed bear greater shares of Australia’s rock-dwelling possum populations. But four biogeographic centers demand checking out by wildlife-lovers who seek to go rock ringtail possum-watching:

• Carpentaria Gulf Country, Kakadu National Park, and the Katherine and Roper River regions in the northerly Northern Territory;
• Groote Eylandt (Dutch for “Big Island”);
• Kimberley in northeastern Western Australia;  
• Lauren Hill National Park in northwestern Queensland.

Northern Australia accommodates rock-haunter needs for:

• Rocky outcrops and sheltered crevices;
• Savanna grasslands and scattered woodlands;
• Scrub forests and wooded lowlands.

Vegetated flatlands allow:

• Crevice- and ledge-sheltered dens;
• Juveniles helping monogamous parents raise newborns;
• Water access within 32.81 – 328.08 feet (10 – 100 meters).

They configure rock-haunters as:

• Competitors to northern brushtail (Trichosurus arnhemensis) and scaly-tailed (Wyulda squamicaudata) possums;
• Dispersers of apple (Owenia vernicosa), blackberry (Vitex glabrata), jujube (Ziziphus oenoplia), and plum (Terminalia ferdinandiana) seeds.
• Predators of blossoms (Darwin’s stringybark [Eucalyptus tetrodonta] and woollybutt [E. miniata]), leaves (prune [Sersalisia sericea] and supplejack [Flagellaria indica]), and termites;
• Prey for dingos (Canis lupus dingo), northern quolls (Dasyurus hallucatus), olive (Liasis olivaceus) and rock (Morelia oenpelli) pythons, and quolls (Dasyurus hallucatus).

The rock-haunter’s diet causes bent cigar-shaped, black- or brown-red scat 0.59 – 0.98 inches (15 – 25 millimeters) long by inches (5 millimeters) wide. Along with scents and urine, coprophragically-reprocessed feces coat branches and posts within home ranges extending 0.0019 – 0.0046 square miles (0.005 – 0.012 square kilometers). Rabbit comparisons likewise hold in:

• Creamy under-sides;
• Grizzled, red- to silver-grey, thick pelage;
• Mature head-and-body length of 13 – 15 inches (33.02 – 38.1 centimeters) and weight of 45 – 70.5 ounces (1.28 – 2 kilograms);
• Rufous (red-brown) rump.

Non-rabbit-like features include:

• Dark stripes mid-backwards;
• Mature, part-furred prehensile tails 7.75 – 10.5 inches (19.68 – 26.67 centimeters) long, with tips at 80+-degree angles;
• Pointed muzzles;
• Two semi-opposable digits per short-clawed “hands”;
• White-patched, rounded, small ears and vertically-pupiled eyes.

Rock possums add survivalist behaviors to rabbit-like coloring and size. Mothers-to-be are thought to deliver 1 newborn 1 – 2 times yearly, March to September. After gestating 16 – 30 days, newborns crawl from the birth canal to the mother’s comfortable frontal pouch. They emerge five weeks later. They experience physical and sexual maturity by age 7 months. They form their own families in overlapping home ranges after:

• Perfecting skills as sentinels perched on branches and ledges;
• Practicing competitor- and predator-warning drills of beating tails against rocks, swinging limbs, and uttering growls and grunts;
• Profiting from parents role-modeling grooming, socializing, and using bodies as bridges between separated branches;
• Put into practice striking tails against branches until entire trees shake.

Every specimen appears distinct when each of Australia's 8 – 9 ringtail possum species lines up. For example, rock-haunters' bright eyeshine avoids the “frozen-in-the-spotlight” hallmark. Their females beat males in size and weight. Both genders care for offspring, who regularly receive ape- and human-like embraces. Both diverge from folivorousness (leaf-eating) by consuming and controlling termite populations. All likewise elude arboreal designations by climbing trees only if food is unavailable on ground-accessible branches and by dwelling among rocks. But they join all ringtail possums in:

• Enduring habitat fragmentation-provoked in-breeding;

• Engaging in heavy-duty scent-marking through anal (male) and chest (female, male) glands;

• Enjoying in protected areas the admiration of visitors and expertise of personnel and researchers.

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

oil on canvas by John Ernest Breun (1862-1921): Kristofer M. Helgen, Roberto Portela Miguez, James Kohen, Lauren Helgen/ZooKeys, CC BY 3.0, via Wikimedia Commons @ https://en.wikipedia.org/wiki/File:Portrait_of_Michael_Rogers_Oldfield_Thomas_-_ZooKeys-255-103-g003-bottom_right.jpeg; via Pensoft Publishers / ZooKeys @ https://zookeys.pensoft.net/showimg.php?filename=oo_25946.jpg

Fotograf / Photographer: Robert Collett (1842-1913): Nasjonalbiblioteket (National Library of Norway), No known copyright restrictions, via Flickr @ https://www.flickr.com/photos/national_library_of_norway/6981537427/
*CC changed from CC BY 2.0 to No known copyright restrictions

Distribution data from IUCN Red List: Chermundy/IUCN Red List of Threatened Species, species assessors and the authors of the spatial data, CC BY SA 3.0, via Wikimedia Commons @ https://en.wikipedia.org/wiki/File:Rock-haunting_Ringtail_Possum_area.png

K.M. Helgen et al., "Twentieth century occurrence of the Long-Beaked Echidna," ZooKeys, vol. 255 (2012), Figure 3, page 107: Pensoft Publishers / ZooKeys, CC BY 3.0, via Wikimedia Commons @ http://en.wikipedia.org/wiki/File:John_T._Tunney_in_front_of_tent_-_ZooKeys-255-103-g003-top.jpeg; via Pensoft Publishers / ZooKeys @ https://zookeys.pensoft.net/showimg.php?filename=oo_25946.jpg

"Northern Quoll photographed between Mareeba and Cairns, Queensland, Australia.": Wildlife Explorer @ Picasa Web Albums, CC BY 3.0, via Wikimedia Commons @ https://en.wikipedia.org/wiki/File:Dasyurus_hallucatus_-Queensland-8.jpg

Robert Collett, "On a Collection of Mammals from North and North-West Australia." Proceedings of the General Meetings for Scientific Business of the Zoological Society of London for the Year 1897, Part II (March 16), Plate XXIII, opp. p. 329: Public Domain, via Biodiversity Heritage Library @ https://www.biodiversitylibrary.org/page/30987497; via Internet Archive @ https://archive.org/details/proceedingsofgen97scie/page/n405/mode/1up; Public Domain, via Wikimedia Commons @ https://en.wikipedia.org/wiki/File:Smit.Pseudochirus_dahli.jpg

Flagellaria indica: Lauren Gutierrez, CC BY-ND 2.0, via Flickr @ https://www.flickr.com/photos/53828064@N05/8684881590

Aboriginal Rock Art, Ubirr Art Site, Kakadu National Park, Australia: Thomas Schoch (Mosmas), CC BY SA 3.0, via Wikimedia Commons @ https://en.wikipedia.org/wiki/File:Aboriginal_Art_Australia.jpg

Groote Eylandt from space, November 1989: NASA, Public Domain, via Wikimedia Commons @ https://en.wikipedia.org/wiki/File:Groote_eylandt.jpg; via Gateway to Astronaut Photography of Earth @ https://eol.jsc.nasa.gov/SearchPhotos/photo.pl?mission=STS033&roll=79&frame=44

Nourlangie Rock, Kakadu National Park, Northern Territory, Australia.: cedventure, CC BY SA 2.5, via Wikimedia Commons @ https://en.wikipedia.org/wiki/File:Pix_9_Nourlangie_Rock.jpg

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