Star, good info but for one thing - they ARE mammals. But there are three types of mammal: placentals (like us); marsupials (like possums, kangaroos, koalas & wombats); monotremes (platypus & echidna, the only egg-laying mammals).
Marsupials generally have similar body temp to placentals but I do beleive you're right in that the US Opossum does have alower body temp. There are anumber of marsupials which have a fairly typical body temp when active, but will go into a cooler torpor whenever they sleep. So if rabies is dependent on maintaining a more typical body heat, then I suspect this would provide a lower rabies incidence rate.
Monotremes even more than marsupials, will have an almost reptilian body temp pattern.
There is a lot of debate about what is a mammal; I remember arguying with easy child's kindergarten teacher who was telling her class that echidnas & platypus are actually marsupials (because they do have a rudimentary pouch).
We KNOW marsupials in Australia (obviously). Australia isn't where they evolved, but it is where they exploited the environment and adapted brilliantly, diverging over the continent. Opossums are, in contrast, restricted in range and more primitive in a lot of ways (not a word I like to use, in terms of an animal's characteristics).
Opossums aren't as cute as our Brushtail Possums but in a lot of ways they are similar. Our possums are protected, completely. However, some idiot took Aussie Brushtails to NZ (to develop a fur trade - Brushtail Possums do have lovely fur) and now they are in plague proportions over there, destroying the NZ environment. So if you ever get the chance to buy NZ possum fur, remember you're doing the world a favour. You can buy it as "Merino Mink" - beautiful and warm.
Back to your Opossums - Janet, you couldwell have a family moved in. Like our Brushies, they are omnivores and opportunistic. They have adapted to human civilisation to scavenge what they can. Our Brushies can make a bit of a mess inside the roof space but as long as they can get in and out easily, they will sleep in the roof during the day and forage at night. The more accustomed to you they become, the more they will consider themselves to be your pets, and come to you for food, raiding whatever you have because OF COURSE you put it there purely for their pleasure.
mother in law has a female Brushie in her (brick) garage. We have lost the resident a couple of times (neighbourhood cats have killed off a couple of possums) and each time, another possum moves in. Vacant possession, like squatters. So if we trapped the possum and had it relocated far enough away (and they will trek back a certain distance if they can) then another one would find the pleasant quarters unoccupied and make them its own.
The best thing you can do, is find out where the possum is getting in, then block up the access (preferably when the beastie is out foraging). You don't want to trap the possum in the roof, especially not in summer. You would have to go in and find the rotting corpse(s) for removal.
We built our house to have no eaves in the roof, so we could keep possums out. mother in law's garage has eaves. Besides, it's brick with a rolladoor, possums will climb a brick wall and they LOVE to sleep inside (or beside) rolladoors.
It's very cold and windy here today. mother in law noted this morning that the possum in her garage is snug and warm out of the wind.
The other thing we do - we have provided a possum box, like a large parrot nest box, tied to a large gum tree in the garden. So if a possum moves in to the nest box, then it will keep other possums away from our property (since they're territorial) and this will of course include any possums wanting to live in the roof. Janet, that might be an option for you - set up a nest box in the garden, wait for the possum to move there (or help it along) and then block up any gaps.
Here is a photo of one of our Brushies - this one has been fighting, it's got a fresh wound on its muzzle.
http://www.google.com.au/imgres?img...vZHMCQ&sa=X&oi=image_result&resnum=1&ct=image
They ARE cute. And more fun than a cat. I was caring for a teenager possum once, she used to ride on my shoulder or sometimes curl up in the bib of my bib 'n brace overalls.
Marg