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10 Cards in this Set
- Front
- Back
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KOALA
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* large marsupial
* Arboreal folivore * Sexually dimorphic - size, sternal gland * Pouch w/ 2 teats * lacks a prehensile tail * Lowest basal metabolic rate of any marsupial |
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Reproduction
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• 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) |
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Development
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• 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. |
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Nutrition & Energetics
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• 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 |
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“Pap” Feeding in Juvenile Koalas
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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 |
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Adaptations to Diet
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• 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 |
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Threats
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• Loss and fragmentation of habitat
• Vehicle injury and mortality • Attacks by domestic dogs • Infectious disease |
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Disease
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• 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 |
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Koala STD?
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• 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 |
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Still Much to be Learned
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• 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??? |
