Lecture 14- Monotremes I (platypus) Flashcards Preview

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What is the classification of a platypus?

-Subclass: Prototheria
-Order: Monotremata
-Family: Ornithorhynchidae
-platypus= 1 species


What are the 6 characteristics that are special about the platypus?

1. cloaca (one hole)
2. lay eggs
3. lactate
4. electroreception
5. low Tb compared to other mammals
6. reptilian pectoral girdle (walk in a push up position, legs not below the body)


What does the pectoral girdle mean in platypus?

-cannot move as fast on land


What does it mean that fossils of platypus were found far inland in Australia?

used to have forests inland, with permanent water


Why are there few echidna fossils?

-don't have teeth and the ancestors didn't either so not preserved


Why is there lot of platypus fossils around?

-ancestors of platypus had teeth and those are more easily fossilised


How old are the oldest fossils of platypus?

-early Cretaceous
-must have existed before that, overlapped with dinosaurs


Do today's platypus have teeth?

-no, born with them but these drop quite early on


Where are the monotremes today?

-Australia and PNG


Are monotremes Gondwanan?

-Yes, found fossil in Patagonia (60MY old)


What are the skulls of the modern platypus and the ancient one like?

-obdurodon species (ancient) were larger, had teeth, extinct about 25MYA)

-today's Ornithorhynchus anatinus is smaller and no teeth


What is the modern distribution of the platypus?

On the east coast of Australia, abundant, not affected too much by european settlement
-cannot live in too high temperatures (38C and above) so global climate change could pose harm to it
-alpine to sea level, north Qld to Tas
-need permanent water


What is the habitat of the platypus?

-permanent lakes and streams, including estuaries (but not marine environments)
-the water can be shallow or deep
-swim near the surface


What are the functions of the burrows platypus dig? (4)

2.predator avoidance
3.avoidance of temperature extremes
4.safe environment for raising young
-use multiple burrows, the ones for young are deeper


Where does the platypus live most of the day and when is it active?

live in water for half a day, rest during the day
-nocturnal typically
-sometimes also active diurnally
-problem with flooding= babies washed out


When do platypus forage?

-from dusk to dawn


What do platypus eat and where do they find it?

-mainly eat aquatic invertebrates
-forage mainly on the stream bed


How do platypus catch their prey?

-use electro- and mechanoreceptors to locate their pray
(eyes and ears are closed under water)
-crayfish= have high lipid content
-crayfish when escaping, tail flip= any movement of the animal= contraction of the muscle= electricity= platypus can detect(can detect very small signals, like 2-3 cm big larvae)


Do platypus have teeth?

-adult platypus don't have true teeth
-have horny plate can exert lot of pressure
-store small prey in cheek pouches and surface to chew
-when attacking crayfish hit and retreat so they don't get caught by the claw/pincer


How much food does a platypus eat a day?

-about 1/3 of its bodyweight
-up to 1/2 of its bodyweight


Where do platypus store their fat?

-in their tail


How can you tell if a platypus is in good shape?

-by the feel of the tail and how much fat there is


How does the male platypus distribution of fat change during the year?

-low during breeding season (July to September)


What type of a breeder the platypus are and when do they breed?

-seasonal breeders
-July to September


Where do the males have their testes?



Do platypus have spurs?

-yes, but only males


Are the spurs poisonous?

-males have crural gland in their thigh connected to the spur that makes toxin
-quite venomous= can kill a small dog and a platypus


Who is bigger, males or females?

-males much larger
-2.7kg but females only 1.9kg the biggest one


Does the testis weight change?

-yes, seasonally


What does an annoyed male platypus do?

-lock in their spurs= very rigid
-when swimming normally then more free