Burramys parvus, Broom, 1895

Russell A. Mittermeier & Don E. Wilson, 2015, Burramyidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 436-455 : 452-453

1.

Mountain Pygmy Possum

Burramys parvus

French: Possum-loir des montagnes / German: Bergbilchbeutler / Spanish: Posum pigmeo de montana

Other common names: Broom's Pygmy-possum, Burramys, Mountain Pygmy-possum

Taxonomy. Burramys parvus Broom, 1895 ,

“New South Wales.” Restricted by R. Broom in 1896 to “ neighbourhood of Taralga, N.SW. [= New South Wales ],” Australia.

This species is monotypic.

Distribution. SE Australia in three isolated populations: New South Wales (Kosciuszko National Park) and Victoria (a population between Mt Bogong and Mt Higginbotham and another distinct population on Mt Buller).

Descriptive notes. Head-body c.11 cm, tail 13.6-13.8 cm; weight 30-82 g. The Mountain Pygmy Possum is the largest species in the family Burramyidae , with both sexes averaging approximately 40 g (although they can reach 70-80 g before the onset of winter). It has fine, dense gray-brown fur dorsally and pale gray-brown to light cream color ventrally; head and back midlines are darker in color. Particularly on males, color becomes bright fawn-orange ventrally and on flanks during the breeding season. Mountain Pygmy Possums have large eyes, dark eye rings, and short rounded ears. Prehensile tail is long, thin, and scaly with sparse, short hair; it is 1-2 times the length of the headbody and shorter than 14 cm in length. Third upper premolar is longer than molars and is grooved or serrated to look blade-like. Females have well-developed pouches.

Habitat. Highland boulder fields (block fields and block streams), rock screes, or boulders scattered around rocky summits. An alpine conifer, the mountain plumpine ( Podocarpus lawrencei , Podocarpaceae ), is typically associated with these rocky habitats. Densities of female Mountain Pygmy Possums are greatest in habitats characterized by high elevations, deep boulder fields, and high abundance of Bogong moths ( Agrotis infusa , Noctuidae ). Presence of heath habitat surrounding boulder fields is important for providing seeds, fruits, nectar, pollen, and arthropods and to allow movement among boulderfields and access to wintering sites and hibernacula, which can be 200 m from primary boulder fields. Lower elevational limit of distribution of the Mountain Pygmy Possum approximates the lower limit of winter snow line at c.1200-1400 m.

Food and Feeding. The diet of the Mountain Pygmy Possum consists primarily of arthropods, especially Bogong moths that migrate from the western plains in spring and spend summer aestivating in cool caves and crevices in the boulder fields, seeds, and berries. Availability of some food items is strongly correlated with elevation, with Bogong moths most abundant at high elevations and seeds and berries more common at relatively low elevations. Arthropods (e.g. moths and beetles) and seeds dominate diets of Victorian populations in November-December and moths in January-April, but moths, caterpillars, spiders, seeds, and fruits dominate diets in New South Wales in December. Nectar is readily consumed by Mountain Pygmy Possums when flowers are available but difficult to measure in their diets; pollen is most abundant in spring. A detailed study of the Mountain Pygmy Possum in Kosciuszko National Park in New South Wales revealed its diet to consist of 71% arthropods, 27% seeds and berries, and 2% other material. The most commonly consumed fruits are from mountain plum-pine, snow-beard heath ( Leucopogon montanus, Ericaceae ), and Pimelea spp. (Thymelaeaceae) in New South Wales and Rubus spp-( Rosaceae ) in Victoria.

Breeding. Breeding female Mountain Pygmy Possums are mostly confined to boulder fields at elevations above 1400 m and to a maximum of 2228 m on Mount Kosciuszko. Breeding females occur at elevations as low as 1200 m at several locations in the north Kosciuszko region. During the breeding season, females typically produce one litter of four young following snowmelt, which can vary with location and year from October to early December. yYoung are born after gestation of 14-16 days and subsequently leave the pouch at ¢.35 days of age and are weaned by 65-70 days of age. Female Mountain Pygmy Possums have been recorded to live up to twelve years and males up to five years in the wild; however, average longevity is usually not more than 2-3 years.

Activity patterns. The Mountain Pygmy Possum is mainly nocturnal, and radiotelemetry studies during the day show that they rest under the surface of boulder fields and scree slopes and occasionally in boles of snow gums ( Eucalyptus pauciflora, Myrtaceae ). Only one nest has been found in the wild. It was 15-20 cm in diameter, spherical in shape, and consisted of long clean strands of leafy moss ( Brachythecium salebrosum , Brachytheciaceae ) with a few blades of grass ( Poa sp. , Poaceae ) intertwined. The moss appears to provide insulative properties that helps keep the nest dry while the surrounding microenvironment, including the soil, may be damp. In captivity, they will also construct small nests with open tops when not breeding.

Movements, Home range and Social organization. The Mountain Pygmy Possum is unique among species of pygmy possums in its seasonal variation of food usage, segregation of sexes, and daily and seasonal movements. In habitats with high densities and elevational gradients, such as at Mount Hotham in Victoria, Mountain Pygmy Possums are sexually segregated during the non-breeding season, with females predominantly at high elevations and males at low elevations. Males in turn move to the higher elevations during the breeding season, with the majority moving to lower elevations by February. Safe movements of Mountain Pygmy Possums across roads and ski runs have been facilitated by construction of corridors and tunnels that are filled with rocks to imitate natural habitat. These allow males to move to female breeding areas, which appear to be an important part of the social organization, and reduce risk of individuals crossing roads. The corridors and tunnels also allow juveniles to disperse and allow the movement of females. At Mount Blue Cow in New South Wales, male and female Mountain Pygmy Possums occupy lowand high-elevation habitats, with individuals from low elevations making excursions to high elevations on a daily basis in January when Bogong moths are concentrated on the mountain peak. Most males and juveniles leave high elevations after the breeding season. Bogong moths are eaten on a seasonal basis to optimize their exploitation on high-elevation peaks in summer, while seeds and berries are used in lower-elevation heaths during late summer and early autumn. Daily movements of both sexes between low elevations and mountain peaks can be more than 1 km in distance and 300 m in elevation during the breeding season, which typically occurs through heathland and boulder corridors. Males can move up to 3 km in a night between boulder fields occupied by females. On sites with little elevational gradient, male Mountain Pygmy Possums typically move to more northerly or westerly aspects in autumn. Home ranges are as small as 0-06 ha on Mount Higginbotham, while on Mount Blue Cow and Mount Buller, home ranges are 0-2-7-7 ha. Reason for sexual segregation of Mountain Pygmy Possums is unclear, but it may relate to the observation that males hibernate at slightly higher temperatures than females, thereby enabling them to arouse earlier in spring, undergo spermatogenesis, and be prepared to breed before females emerge. It may also relate to energetic and reproductive constraints limiting females to high-quality habitat or suitable nesting areas with a relatively low risk of predation. In turn, males may be forced into habitats at low elevations containing poorer resources after breeding by the collective aggression of high densities of females. Mating system of the Mountain Pygmy Possum appears to be promiscuous, with multiple paternities of litters. In situations where densities of females are very high, such as on Mount Higginbotham, the breeding system has been described as matriarchal polygyny, with females defending resources from males.

Status and Conservation. Classified as Critically Endangered on The IUCN Red List. The Mountain Pygmy Possum occurs in only three genetically isolated, regional populations. These populations are separated from each other by low-lying river valleys in alpine regions in south-eastern Australia and occupy a combined area of less than 6 km?*. A series of population declines of Mountain Pygmy Possums on sites with the highest densities between 1997 and 2010 were coincident with a long period of drought and high temperatures in south-eastern Australia. New colonies have also been recently discovered at Snow Ridge and Rough Creek, which are generically associated with those in Kosciuszko National Park. The Mountain Pygmy Possum is highly susceptible to global warming because duration of snow cover and time of snowmelt appear to be linked to survival rates. Climatic modeling indicates that the Mountain Pygmy Possum will disappear with a 1°C rise in mean annual temperature, of which 0-5°C of warming has already occurred since 1980. The little remaining habitat is also vulnerable to clearing and modification for ski-run development. Critical components of conservation of the Mountain Pygmy Possum include protecting habitat within the very limited distribution that remains and migration corridors among habitats.

Bibliography. Brereton et al. (1995), Broom (1895, 1896, 1898), Broome (2001a, 2001b, 2008), Broome & Mansergh (1989), Broome, Archer et al. (2012), Broome, Ford et al. (2013), Caughley (1986), Common (1954), Gibson (2007), Gullan & Norris (1984), Heinze & Olejniczak (2000), Heinze & Williams (1998), Heinze et al. (2004), Hume (1999a), Kerle (1984a, 1984b), Kortner & Geiser (1995), Mansergh (1984a, 1984b), Mansergh & Broome (1994), Mansergh & Scotts (1986, 1989, 1990), Mansergh et al. (1990), McCarthy & Broome (2000), Menkhorst, Broome & Driessen (2008), Osborne et al. (2000), Schulz et al. (2012a, 2012b), Smith & Broome (1992).

Figures

1. Mountain Pygmy Possum (Burramys parvus), 2. Long-tailed Pygmy Possum (Cercartetus caudatus), 3. Western Pygmy Possum (Cercartetus concinnus), 4. Little Pygmy Possum (Cercartetus lepidus), 5. Eastern Pygmy Possum (Cercartetus nanus)

Distribution. SE Australia in three isolated populations: New South Wales (Kosciuszko National Park) and Victoria (a population between Mt Bogong and Mt Higginbotham and another distinct population on Mt Buller).