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10 Cards in this Set

  • Front
  • Back
* large marsupial
* Arboreal folivore
* Sexually dimorphic - size, sternal gland
* Pouch w/ 2 teats
* lacks a prehensile tail
* Lowest basal metabolic rate of any marsupial
• Males have sperm more similar to eutherian pattern than other marsupials (except wombats)
• Females are induced ovulators with a long oestrouscycle and gestation compared to other marsupials
• The Koala is one of a very few marsupials that retain a chorio-allantoicplacenta (Placenta- which is universally found in eutherianmammals)
• Typical of marsupials, the baby is quite altricial at
birth, but climbs unaided into the mother’s pouch
• There it attaches to a teat
• It’s then raised on milk for about 5 months, when it starts to poke its head out and nibble leaves
• It first leaves the pouch for short periods at about
6 months of age- then rides on mother’s belly, then back until independent at 12 –15 months age.
Nutrition & Energetics
• Koalas have evolved to use a food resource that was effectively unlimited & “constant”, but of very poor nutritional quality
• Koalas have the biggest caecum relative to body
size of any mammal but only rely on cellulose fermentation for about 10% of energy needs
• Nonetheless they have a very distinctive gut flora & fauna essential for proper nourishment
• It’s a major problem for an arboreal folivore to establish these gut microbes in its progeny
“Pap” Feeding in Juvenile Koalas
When young Koalas begin to
nibble leaves, an unknown
mechanism induces their
mother to evacuate caecal
contents which the babies
avidly consume (poop!)
Allows proper processing of a gumleaf diet by the gut
Adaptations to Diet
• Energy Conservation
- Lowest Basal Metabolic Rate for any marsupial
- Highest Insulative Value Fur for any marsupial
- Behavioural
Inactivity –normally rests for 16-18 hours per day
• Postural and roost position adjustment
• Selects mostly “Tip Growth” for browse
• Loss and fragmentation of habitat
• Vehicle injury and mortality
• Attacks by domestic dogs
• Infectious disease
• Even though it is largely secondary to the other threats, infectious disease can be devastating
• Mostly due to bacteria in the Chlamydia group
• Affects eyes, urinary tract, reproductive tract, respiratory tract
• Treatable- particularly effective for eye disease
Koala STD?
• In popular reports about chlamydiosis in Koalas, it’s asserted that the infection is
sexually transmitted
• Whilst this is probably true in some cases, it’s a serious oversimplification
Still Much to be Learned
• Koalas have a caecum that is relatively the biggest known for any mammal, but it appears
relatively little of its energy requirements come
from breakdown of cellulose –so what’s it do?
• It’s recently been discovered that female Koalas
have vestibular glands –what do they do?
• The males are the only mammal known other than Homo sapiensto have crystalloids in the Sertolicells of their testes as a normal feature –
what is their significance in either species?
Koalas never drink
Why do they eat dirt???