lecture 7 - mammals of fraser island Flashcards
what animals came to australia in the Early jurassic?
> ~200mya
> monotreme ancestors diverged early in ‘gondwana’ and spread throughout the southern globe, probably
what animals came to australia in the early cretaceous?
> ~120mya
placentals probably split form metatherian ancestors in asia
placentals also dispersed but few reached australia at this time
because of land ridges
what happened in late cretaceous?
> ~105mya
> passage to australia was getting more difficult because it was separated from gondwana by water
what happened in the K/T event
> wiped out the dinosaurs and many other things.
opened to way for remaining mammals to diversify
in gondwana, the S.American mixture evolved in isolation
in Australia, the marsupials radiated
new cicumpolar currents started to freeze antartica
how did the mass extinction event allow for the radiation of marsupials?
> wiped out a lot of animals - thus creating empty niches
> these niches were then filled by the marsupials
what happened by the oligocene?
> ~35mya
> australia was on its way to warmer and drier climates, shaping the organisms that live here
what are prototherians/monotremes?
> neonates hatch from an egg laid in pouch
earliest strain
what are metatherians/marsupials?
> neonates born early and develop in pouch attached to teat
what are eutherians/placentals?
> neonates born after development supported through a chorioallentoic placenta
what sub-class and order is the short-beaked echidna in?
> subclass Prototheria > order Monotremata
what subclass and order is the yellow footed antechinus in?
> Marsupialia > Dasyuromorphia - hop - rat/mice sized - insectivourous
what subclass and order is the common dunnart in?
> marsupialia
dasyuromorphia
- teeth are pointy for piercing prey
what subclass and order are long-nosed bandicoots in?
> marsupialia
Peramelemorphia
- pointy front teeth, then molars for grinding
what order and subclass are northern brown bandicoots in?
> marsupialia
> peramelemorphia
what is the subclass and order of the short-eared brushail?
> marsupialia
> Diprotodontia
what subclass and order are swamp wallabies in?
> marsupialia
>diprotodontia
what happened in the pleistocene?
> ~50,000mya
the australian plate collided with the asian plate forming an opportunity for new mammals to add to the fauna
HOWEVER, there is trace evidence of placentals already being here as early as the Eocene (50mya), before the final split from gondwana
there are a few teeth and jaw fragments from murgon controversially assigned to a placental, plus a fossil bat
presumably these managed to disperse here from the south, but they didn’t persist
during which era did multiple waves of invasions ocur
> pliocene
what different organisms are in the sub-class Eutheria ad Order - Rodentia
> a mosaic tailed rat whose ancestor arrived after the first ‘old endemics’ and before the ‘new endemics’
fawn-footed melomys
bush rat
have typical rodent dentition
what is in the subclass -eutheria and order Chiroptera
> gould’s wattled bat
> a micro-chiropteran’ that uses echolocation
when were all the new endemics present before?
> 1760
what sub class and order are black rats in?
> eutheria
> rodentia
how do you make abundance estimates?
> mark and recapture
if you know what proportion of the population you catch, then you know the size of the population, sort of.
trap initially and mark all the animals you catch.
trap again and see what proportion are marked
assume all your marked animals mix into the population in the meantime
all animals, marked and unmarked are equally likely to be caught
and the population size has not changed
of your recaptured animals, the proportion of marked animals in the second event gives an estimate of the proportion you catch in any event
apply this to the first event to get the original population size
what is an example of the mark and recapture technique?
> suppose you trap 30 animals the first time round. you mark and release them.
suppose you then trap 25 animals, 5 of which are marked
based on a single estimate so far, your traps successfully retraped 5 in 25, or 1 in 5 animals
so you assume that your first trapping event successfully trapped 1 in 5 animals, i.e., there were 150 (5x30) animals out there
what are some assumptions of the mark and recapture technique?
> animals are equally likely to be trapped each time
- not always the case
- trap happy or trap shy animals
how can you improve the precision of mark and recapture?
> increase the number of samples taken
often its possible to treat multiple trapping events as serial estimates, leading to greater precision
in any case, its better if you trap heaps of animals, not just a few
