Lecture 16- Marsupials: Koala Flashcards
What class are the koalas in?
Mammalia
What subclass are the koalas in?
Theria
What infraclass are koalas in?
Marsupialia
What order are koalas in?
Diprotodontia
What suborder are koalas in?
Vombatiformes (wombats and koalas)
What family are koalas in?
Phascolarctidae
What is koala’s distribution?
- approx. 1 million km squared
- approx. the area of Japan
- koala is not a species most at risk
- coastal East Australia
What is koala habitat like?
-forests, Eucyalyptus woodlands, containing preferred Eucalyptus species
What is ranging behaviour like in koalas?
- adults are sedentary
- have small ranges (in SE Australia)
- larger home ranges in dryer areas in the north
What do koalas eat?
- Eucalyptus leafs,
- species depends, can eat more than one
Why is it surprising that koalas are arboreal?
- no tail!
- large body size (males up to 15kg which is the approx. upper limit for arboreals)
How are koalas adapted to arboreal life?
- excellent climbers
- claws and feet adapted for climbing
- can jump sometimes but not that good at it and dangerous
How did koalas become arboreal?
- secondarily arboreal
- wombat and then went up
What is the koala diet?
- specialist folivore, feeds almost exclusively on foliage, from a limited number of (mainly) eucalypt species, these vary regionally
- sometimes feed on peppermint
Why are koalas not very active?
-foliage is poor quality diet, hence not very active
What are the constraints on herbivore digestion?
- structural plant material is hard to digest (cellulose) is difficult to digest
- dependent on bacterial and protist cellulases (diverse protist and bacterial microfauna in the gut-symbiotic microorganism)
- food preparation: fine particles
How do koalas prepare the food they eat?
- cutting molars (4 cusps on each), they cut, chop the leaves, older koalas
- then less efficient digestion (worse surface to area ratio), die of starvation eventually
What are secondary metabolites in plants?
- chemicals that help plants resist herbivores
- anti-feedants
- vary between species (phenolics=tannins, terpenoids=essential oils)
- secondary= because no know primary function in the plants
===species need to be physiologically specialised to feed successfully on such plants
What are the tactics to deal with plant secondary metabolites (PSMs)?
- avoidance
- dilution
- degradation
- detoxificantion
What is the importance of nitrogen in home ranges?
PSMs limit nitrogen available to animals= low reproductive success and habitat selection
How are PSMs deactivated/detoxified?
- absorption from gut then conjugation in liver (via microsomal enzymes, endoplasmic reticulum), water soluble conjugates are excreted in urine (kidney) or bile (gut)
- urine smells like eucalyptus
When do koalas mate?
- spring- summer
- November to March
How long is pregnancy?
35 days
How many young per year?
1, (some populations breed more slowly due to chlamydia)
How long is lactation in koalas?
12 months
What is the juvenile survival like?
-high
When are koalas sexually mature?
at 2 years of age
How does koala weight change due to lactation?
- weight loss in late lactation due to high energetic load coupled with low quality food
- they carry the baby on their back, costly energetically
- they drive the baby off when new one in the pouch
How do males and females differ?
- males much larger than females
- care of young is maternal only
- males fight
- males bellow
- males scent mark = chest gland= rub it on trees to mark territory
What do males bellow for?
deep and loud, signal to females to know where the males are
-also tells other males where they are
Why do many males fall off the tree?
males fight, common in dense population
-the males fall off the tree, mostly when 3.5 yrs old when trying to get into the breeding population
What is the morphological change in characters across a species geographical distribution (latitudinal cline) = gradual change in characteristics from north to south?
- fur length or thickness
- colour
- body size
- shape
What is Bergmann’s rule?
-medium to large sized mammals with large distribution usually exhibit larger body size in colder areas
(shorter ears, to conserve heat)
What is the morphological cline in koalas?
- north: shorter paler fur, adult males up to 9.1 kg (most 7-8)
- south: longer darker fur, adult males up to 15kg (most 11-12.5kg)
- large body size an advantage for males in fights
What are the problems koalas face?
- differs from place to place
- cyclones= trees defoliated, drought= trees defoliate
- wild dogs hunt them (ones that ran away from people)
- habitat destruction and fragmentation due to human inhabitation
Why are some koala populations declining?
- habitat loss and fragmentation= land clearing and urbanisation
- increased mortality (cars and dogs)
- low fertility (chlamydia)
-happens when mortality is larger than recruitments= then population decline
Why are some koala populations increasing?
- high fertility, rapid population growth
- occur in habitat isolates (like reserves etc,.)
What are the management techniques for overpopulated koalas?
- relocation to other habitats so they don’t kill their food trees)
- fertility control=hormone implants for females= very effective and do not harm the animals
- habitat protection and restoration
What type of digestion do koalas have?
- -hindgut fermenters, have gut 6-7 long
- long gut passage time= as need time to digest
