Lecture 17- Australian Native Animal Nutrition

Question 1

What is the case with crocodiles?

Answer 1

• In-discriminant and opportunistic feeders
• Increases in body size increases prey size (insects to vertebrates like cattle)
• Digestive energy costs are high
• Stomach capacity 3-15% bodymass
• Lower than reptiles like pythons
• There has been research into commercial crocodile diets • Pellets etc.
• American alligators have been successfully fed a veg based pellet
• Most active at night
• Will eat anytime prey is present

Question 2

What do crocodiles eat?

Answer 2

• Little is known about the nutrient requirements
• Farmed animals do respond to differences in nutrient intake
• Do not need to feed daily
• But increased number of feedings improves efficienc

Question 3

What are the characteristics of kangaroos?

Answer 3

• Macropods
• Dental structure varies between species • 32-34teeth
• Molar teeth are replaced as the animal ages (up to 5 sets) • Large single pair of lower incisors
• Some macropod species eat invertebrates, fruits & seeds (musky rat kangaroo) • Browsers (quokkas, swamp wallabies) eat shrubs & soft plants
• Grazers feed predominately on grass

Question 4

What is kangaroo digestive tract like?

Answer 4

• Swamp Wallabies (& others) have an unusual oesophagus lined with numerous papillae
• Foregut fermentation
• Anatomy very different to ruminants
• Oesophagus opens into funnel shaped region
• Extends along inner curvature of the stomach
• Separates coarse from fine plant materials
• Fine material → hindstomach
• Secretes HCl & proteolytic enzymes
• Coarsematerial→forestomach
• Bacterial fermentation, largest section
• Similar VFA production to sheep
• Divided into sacciform & tubiform forestomachs
• Glandular & secretes mucus
• Smallcaecum&colon
• Water absorbed in distal colon

Question 5

What are more details about kangaroo nutrition?

Answer 5

• Monovular
• Polyoestrus (22-46 day cycle)
• Ovulation occurs a few days before or after parturition
• If conception occurs the zygote will develop to blastocyst then enter diapause for as long as
lactation occurs
• Thus conception does not interrupt the oestrus cycle, lactation does.
• Does not happen in western grey, musky rat or the tree kangaroos
• Unique lactation
• Sustains neonate from embryonic form to after birth (can be over 1 year)
• Milk composition markedly changes throughout lactation

Question 6

What are the characteristics of koalas?

Answer 6

• Has few natural predators
• No specific requirement for shelter
• Little to no resource competition
• Thus food is the major determinant of habitat quality
• Very low basal metabolic rate

Question 7

What is the koala diet?

Answer 7

• Specialised folivore of Eucalyptus
• Folivore = herbivore that specialises in eating leaves
• Will eat from many (>120) different trees within their range • Eat from both Eucalyptus and non-eucalypts
• Prefer certain eucalypt species over others • Not as fussy as believed
• Do eat from many species and are rather generalist
• Select feed based on morphology and chemistry • Andpalatability

Question 8

What is koala’s digestive tract like?

Answer 8

• Long retention time for food
• Maximises nutrient extraction and absorption
• MRT > 100 hrs!
• Influenced by age and status
• Long caecum (200 – 2000 cm)
• Largest in relation to body size of all mammals • Hind-gut fermentation
• Teeth designed to tear and shear leaves • Teeth wear with age

Question 9

How much do koalas eat?

Answer 9

• How much do Koala’s eat?
• Like all species this is dependant upon the nutrient content of the feed
• Dietary preferences influence intake • Species offered etc.
• Estimated intake ranges from 14 – 57 g kg-0.75 per day • About 500g per day
• Other factors influence intake
• Tree size: larger trees preferred (to sit in) but may not necessarily have high quality feed
• Seasonal variation: leaf age (young is preferred), toxic compounds, leaf water content etc.
• Regional variation: location changes tree type and preferences. Captive Koalas also will have little ‘choice’

Question 10

How does nitrogen figure in koala nutrition?

Answer 10

• Koala’s select for low fibre
• Nitrogen levels vary but generally Koala’s will select for higher nitrogen contents
• 1.1% total nitrogen preferred (but

Question 11

What is a platypus?

Answer 11

• Freshwater egg laying mammal
• Semi-aquatic
• Relatively unchanged since the time of dinosaurs
• Consume insects, molluscs, worms, eggs (larvae), small frogs etc. • Dive for

Question 12

What is platypus physiology?

Answer 12

• Cloaca
• Common hole for urine and fecal excretions and reproductive organs
• Poor vision
• Venom gland in thigh and spur
• Only used once sexual maturity is reached • Spur used to determine sex and age
• Toxic to smaller mammals (not humans)
• Simple digestive tract
• Bill used for sensing food
• Adults do not have teeth (small teeth in early life but these are lost) • Adults have keratinous grinding pads (grind food thoroughly)
• Small stomach and short gut transit time (~5 hrs)

Question 13

What is an echidna?

Answer 13

• Egg laying monotreme
• Thick skin with fat layer
• No nipples
• Milk expressed into pouch skin via hair follicles
• Beak has receptors to sense food • Produce lots of saliva
• For food but also nasal secretions due to sniffing
• Small eyes but good vision
• Better colour vision than humans?

Question 14

What is the echidna digestive system like?

Answer 14

• No teeth
• Food secured by the tongue & sticky saliva
• Termites, ants etc.
• Tongue can be extended 18cm beyond the snout
• Can protrude and retract >100 times per min
• Prey items crushed between tongue and hard palate • Simple monogastric digestive system
• Stomach is non-glandular and does not digest protein • High pH of ~6.2
• Lined with stratified epithelium to grind food
• Slow passage rate of food (~2 days)

Question 15

What is echidna nutrition like?

Answer 15

• Prefer termites to ants
• Diet is high protein and high fat
• Get most of their water from food • Termites can be 80% water
• Often fed meat etc. in captivity • Obesity can occur

Question 16

What is a wombat?

Answer 16

• Mainly nocturnal
• Herbivores
• Hindgut fermentation
• Simple stomach
• Short small intestine
• Large sacculated colon
• Small caecum
• Teeth designed for grazing high fibre grasses
• Rootless teeth that continually grow
• Each jaw has: 1 pair incisors, 1 pair premolars &4 pairs of molars
• Split upper lip – allows teeth to pick up grass from the ground
• Grind food quite finely
• Low energy & protein requirements
• Good recycling of urea
• Low BMR
• Body temp 34-35°C
• Lowest concentration of thyroid hormones of any animal

Question 17

What do wombats eat?

Answer 17

• Proteins & Carbs digested in stomach • Absorbed in small intestine
• Slow rate of passage • 3-8 days
• Graze for 2-6 hrs per day
• Most energy is derived from the bacterial fermentation in the colon
• Faeces are amongst the driest of any animal
• Gain most water from food
• Only drink when hot
• Will remain in burrows during extreme temperatures


Question 18

What are possums?

Answer 18

• Mainly nocturnal
• Varied habitats
• Varied diets
• Pollen & nectar (pygmy possums)
• Invertebrates
• Leaves, fruits, flowers, seeds, sap etc. • Occasionally meat (brushtails)
• Varied teeth depending on type
• Simple stomach and expanded caecum
• Hindgut fermentation
• Common ringtails are coporphagic

Question 19

What is coprophagy like in possums?

Answer 19

• Two types of faeces are produced
• Caecotrophs (large, soft moist pellets) produced from the caecum • Produced in daylight hours & immediately eaten
• Ensures efficient nutrient absorption
• Harder faecal pellets passed during the more active night periods

Question 20

What do kookaburras eat?

Answer 20

• Kingfisher birds
• Mainly eat mice, small snakes and lizards
• Also small birds, crickets, worms & other insects • Regurgitate undigested materials as a pellet
• About once per day
• Adults will ‘bash’ prey on perch to break up bones • Food is swallowed whole
• 2-3 mice per day consumed

Question 21

What are the characteristics of turtles?

Answer 21

• Ectothermic
• Regulate their temperature via the external environment & behaviour • Body temperature can be higher than the external environment
• Species in cooler environments (like Vic) will bromate • Hibernation-like state
• Lethargyetc.
• Species in warmer environments will aestivate • Inactivity
• LowersBMR
• Modern turtles lack teeth
• Beak like mouths grind food
• Feet shred food
• Long necked turtles ‘ambush’ feed
• Short necked turtles also eat vegetation

Question 22

What is turtle nutrition like?

Answer 22

• Turtles will eat live or dead fish, prawns, yabbies and insects • Opportunistic feeders
• Can gorge themselves in preparation of food shortages
• Very slow rate of digestion
• 2-6 weeks for complete digestion to occur
• Feeding red meat can be dangerous as it can cause toxin build up • Adults only need to eat every 4-5 days
• Low BMR
• Foods high in phytic acid can be dangerous • E.g. peas & corn
• Phytic acids can bind minerals (calcium & magnesium) & prevent absorption

Question 23

What do pelicans eat?

Answer 23

• Mainly eat fish
• Will eat crustaceans, tadpoles & turtles • If starved will eat ducks, seagulls etc.
• Bill & pouch important
• Bill locates fish & has hook to grip food
• Pouch formed between lower jaw (thin bones) • Pouch can expand to hold 13 L!
• Pouch does not hold food for long

Question 24

What do dingoes eat?

Answer 24

• Australia’s largest territorial predator • Anatomy is basically identical to dogs
• But vastly different behaviour & reproduction
• Will eat insects, lizards, rabbits, birds, sheep, cattle & horses
• Eat about 7% bodyweight per day • ~1kg per day for adults
• Require about 100mL water per day in summer