Marsupial Structure and Function Flashcards
Social structure
- Considerable diversity
- Long-term bonds between males and females rare
- Exclusive home ranges of individuals uncommon
Solitary species
- Smal, nocturnal carnivores or omnivores
- Densely vegetated habitats where food is dispersed and requires individual hunting
- Males and females come together for mating only
- Promiscuous or polygynous mating system
Group-living species
Small, stable groups
- advantageous to males in groups, as they are present at the right time for breeding
Large, unstable groups
- increased size, mobility, diurnal activity, specialisations for utilising grasses in open areas
- Hierarchal, promiscuity/polygyny
Sexual Size Dimorphism
- One sex is significantly larger than the other
- Usually indicates competition for access to mates
- The few monogamous marsupial species have no sexual dimorphism
Behaviour: Communication
- Olfactory (chemical) - specialised skin glands
- Auditory - vocalisations and other auditory queues
- Visual - trichromatic vision
- Tactile - grooming, passive contact
Behaviour: Activity and Rest
Activity
- Mainly nocturnal
- Some active in daylight, esp. dawn and dusk
At rest
- Shelter in constructed nests, burrows, hollows or logs
Thermoregulation
COLD
- Increase MR
- Huddling in groups
- Torpor
HEAT
- Behavioural
- Panting, sweating, licking
Cardiorespiratory function
Compared to eutherians:
- 30% heavier heart
- Lower resting heart rate
- Similar max heart rate
- Lower resting respiratory rate
Metabolism
- Resting body temp 2-3 degrees lower than eutherians
- Lower BMR (lower nutritional requirements, can increase significantly in response to cold)
Neurological System
- Small brain
- Large olfactory bulbs
Integumentary System (skin)
- Cutaneous scent glands - common vestibule, forehead, ears, pouch, sternum
- Endocrine sweat glands - paws and tail
- Volplane (gliding) membrane
Musculoskeletal structure
Compared with eutherians:
- Hard palate fenestrated (having perforations, apertures)
- Epipubic bones
- Lack fully developed patella
Musculoskeletal structure - Skull
- Large facial area
- Small cranial cavity
- Narrow oral gape
Musculoskeletal structure - Forefeet
- Some climbers have forcipate hand (digits 1 and 2 opposable)
Musculoskeletal structure - Hindfeed
1st digit may be:
Reduced/absent (kangaroos)
Strong and used for prehension (possum)
Digits 2 and 3 may be syndactylus
Saltatation
“Hopping”
- Energetic advantages certain animals at certain speeds
- Top kangaroo speed = 70km/hr
GIT: Carnivores/insectivores
Very simple
- Simple stomach
- No caecum
- Small and large intestine short with similar diameter
GIT: Omnivores
- More complex to deal with plant material
- Salivary glands larger
- Large intestine more developed (fermentation)
- Caecum generally large
Special features of Diprotodont
Wombats - open rooted teeth that grow continuously
Wallabies & kangaroos - sequentially erupting molars. Teeth shed as they are worn out –> prolongs time with good quality teeth
GIT: Herbivores
- Greater development of salivary glands
- Greater expansion of gut for fermentation
GIT: Foregut fermenters
- Stomach expanded and sacculated
- Long small intestine
- Colon and caecum well developed
Kangaroos and wallabies
GIT: Hindgut fermenters
- Microbial fermentation occurs in enlarged caecum and/or colon
- Simple stomach
Wombats, koalas, possums
Problems for hindgut fermenters
- Less opportunity to absorb microbial amino acids and B vitamins (some use caecotrophy to overcome this)
- Disturbance of gut flora by antibiotics
