Koala (Phascolarctos cinereus) Fact Sheet: Behavior & Ecology

Most often described in literature as nocturnal, with some activities occurring during the day
Recent study, however, of 59 radio-collared individuals on St. Bees Island, Queensland revealed koalas travel nearly the same distance in the day as at night (Ellis et al. 2009)

• Ranged an average of 53.6 m (176 ft) during day
• Ranged 63.3 (208 ft) at night

• Nighttime tree for feeding often not same tree used in day for resting

An adult spends about 19-20 hours/day sitting, sleeping
In a study of koalas at the San Diego Zoo,

• 1 to 4 hr/day feeding; remainder of active time grooming, moving between trees, social activities (Jackson 2007)

• Foraging is done in 4 - 6 sessions per day, each lasting about 20 minutes to 2 hours

Low energy lifestyle is necessary for animal that specializes on such a low energy diet
Posture changes help with body temperature regulations (Lee & Martin 1988)

• Hot day - limbs extended, dangle on either side of tree
• Cold, wet windy day - arms folded against chest, legs drawn against belly

Studies of breeding dynamics in koalas at Blair Athol, central Queensland revealed (Ellis et al. 2001) (Ellis et al. 2002b):

• Whether resident or transient, male koalas are equally likely to sire offspring; resident status offers no advantage
• Home ranges of males and females show no size differences

Home range

• In a 6-year-study of koalas wearing very-high-frequency radio collars on 20 ha (46 acres), St. Bees Island, Queensland (Ellis et al. 2009):
  • Shared 1.78 ha, or 25.5% of home range with other koalas
  • Each koala shared a home range with at least 7 other koalas
  • Home range overlap not influenced by sex of koala
  • Even when ranges overlap, koalas rarely share trees (don't share food resources)
  • Distribution of koalas perhaps more influenced by social factors than features of the landscape
• Size of home range varies within and across populations (Martin 2001)(Martin & Handasyde 1999):
  • 6 ha to 300 ha (15 acres to 741 acres

Koala males may be territorial or non-territorial (Melzer et al 2010)

• Mainland central Queensland koalas:
  • Highly territorial
  • Large non-overlapping ranges
• Victoria males:
  • Non-territorial

Viewed as non-social but live alone within a complex community (Ellis et al. 2009)

• Regulated by a complex communication network
• Tend to occur in clusters of overlapping home ranges
• Foraging and social strategies evolved together to exploit patchy resources without direct competition

86-89% (breeding season) to 93-96% (non-breeding) time spent alone

Aggression:

• Most often occurs when one animal enters an occupied tree
• Depending on level of dominance, either invader or resident can be the aggressor
• Male-male (Mitchell 1990a) (Melzer et al. 2010):
  • Usual response to aggression - submission
  • Actual attacks between males with major fights rarely observed. (Mitchell 1990a) (Melzer et al. 2010)
  • One male usually ends up leaving, but will not be chased beyond the base of the tree
  • Usually seen in males at least 4 years old
  • Most observations of fighting between males made in settings in confined enclosures
• Example of aggression between radio collared male and another male in tree in central Queensland (Melzer et al. 2010):
  • Intense bellowing
  • Harsh grunting
  • Growling
  • Biting
  • Scratching
  • Wrestling
  • Climbing higher in the tree
  • Both animals falling out of tree to ground
  • One male dies 2 months later, perhaps due to depressed immune syste

Signs of stress:

• Continuous ear flicking
• Hiccups
• Low whining vocalization
• Alarm posture with wide eyes, ears forward, spine vertical

Bellowing by males studied in wild, using GPS on both sexes, on St. Bees Island, Australia (Ellis et al. 2011):

• Extremely low frequency sounds
• Has inhalation and exhalation phase
• Number of bellows peak just before the peak of breeding activity
• No significant link seen between bellowing and other males' movements
• Bellowing does influence female travels: (Ellis et al 2011)
  • They travel more when more bellowing is occurring
  • They probably are searching for males
• Sound production potentially unique among mammals (Charlton et al. 2013)
  • Not produced by laryngeal folds as in other mammals
  • Folds in the velum, velar vocal folds, vibrate to produce low frequency sounds (10-15 Hz)
    • Velum also known as the soft palate
    • Located at the back of the throat; intersection between the oral and nasal tracts

Besides bellowing, four types of encounter calls: (Mitchell 1990a)

• Squawks:
  • Short, harsh
• Snarls:
  • Longer (up to 2 seconds) than squawks
  • Atonal to moderately tonal
• Screams:
  • High pitched
  • Sound travels farther
• Wails:
  • Longer than screams, similar to wail of domestic cat
  • Uttered by females or young in distress

Click here for Koala sounds, provided by The Cornell Lab of Ornithology, Macaulay Library

Play

By young animals
Solitary or with another
Climbing and jumping or chasing one another

(Tobey et al. 2009)

Both males and females use urine and feces to scent mark objects in their environment
Males also use sternal gland on chest to leave chemical signals, mostly at the base of trees

• Males at least 4 years old
• This activity most frequent during breeding season
• Complexity of chemical signal increases with age and during mating season
  • May be regulated by reproductive hormones
  • May convey information regarding sexual maturity, health, individual identity, dominance rank

Arboreal, but must travel on the ground to move to another tree or stand of trees; travel on all fours (Grand & Barboza 2001)

• May cross up to 10 km (6.2 mi) or more of land between stands of trees
• With long digits and curved claws, hands and feet don't rest flat on the ground
• Pelvis and hip are inflexible and the gait involves much side-to-side movement
• Limb movements aren't coordinated or smooth

Males tend to move to new trees more often than females

Climb

• Bound up rapidly, using strong hind legs to push them up
• Alternatively, climb slowly, using arm, then opposite hind limb
• Recurved claws and opposable digits help them grasp trunks and branches
• Climb down a tree with head facing up

Sitting posture facilitated by typical branching pattern of Eucalyptus trees (Grand & Barboza 2001):

• Brances grow outward in acute angle to trunk, giving koalas a good place to wedge themselves securely

For their slow deliberate movements, koalas have one-third less muscle mass than their faster wombat relatives (Grand & Barboza 2001)

Dingos and humans today are only significant natural predators on adult koalas. (Smith 1987)

• Dingos were introduced between 3,500 and 12,000 years ago by humans (Savolainen et al. 2004)

Preyed on by wedge-tailed eagles on St. Bees Island (Melzer et al. 2003)
Other raptors prey on koalas on mainland
Possible Pleistocene predators: (Wroe 2004) (Tyndale-Biscoe 1995)

• A large marsupial lion (Thylacoleo carnifex)
• A giant Komodo dragon Megalania prisca, up to 5 m (16 ft) long
• Pythons, up to 6 m (20 ft)

Dependent on a diet of Eucalyptus that’s low in calories, koalas survive with a low metabolism and a habit of sleeping or sitting 20 hours a day. Dense wooly fur cushions the koala from branches and protects from extremes of the weather.

Image credit: © BlacktouchYellow from Flickr. Some rights reserved.

Charlton et al. (2013)
Eberhard (1978)
Ellis et al. (2001)
Ellis et al. (2002b)
Ellis et al. (2009)
Grand & Barboza (2001)
Jackson (2007)
Lee & Martin (1988)
Martin (2001)
Martin & Handasyde (1990)
Melzer et al. (2010)
Mitchell (1990a,b)
Savolainen et al. (2004)
Smith (1979a)
Smith (1980a,b,c)
Smith (1987)
Tobey et al (2009)
Tyndale-Biscoe (1995)
Wroe (2004)