The care guide with pictures

The Enclosure
Animals kept in captivity may get stressed in environments they feel exposed or which don't allow them to do the instinctive behaviors that kept them safe in the wild. Their little bodies say "if I'm prevented from doing _X_, I cant kept myself safe!". Sometimes this stress leads to undesirable behaviors. Stressed animals may act aggressive or nervous. They may hide, panic, or be quick to bite. Animals may also perform unnatural, repetitive actions. These behaviors are called "stereotypies" and include things such as bar biting, pacing, feather plucking, rocking etc.

In STOs I've seen a wide variety of ways they have responded to stress. They pace (in STOs I've noted patterns around the cage as opposed to back and forth), bar bite, change activity patterns, run, bite, attempt to hide in shallow depressions of bedding etc. Its important to understand these stress behaviors aren't personality traits of the of the animal, they are symptoms of a much bigger problem. Stress not only makes them less fun as pets, but increases their risk of a wide variety of seemingly unrelated health issues. For some, trying to tame them when they are under this type of stress will at best do nothing and at worse make them much more fearful of you.

Keep in mind STOs are up a lot when you're not around and most people don't know what behaviors to look for. "They seem happy" isn't a good measure that the care is meeting their needs-- I've found it one of the cruelest justifications I hear. Its a pretense that the owner "cares", but its used to justify not doing something for the animal out of convenience. Owners that do care try out lots of things known to help their pets and are willing to change to keep up as they learn.

Our primary goal is to learn what STOs need to thrive and how to tell when they aren't getting it (babies are a cute bonus). I have spent years reading papers, watching them, and seeing others' experiences. I've gained so much information I've not seen elsewhere.

Our care guides include the methods and items we've found, so far, effectively reduces their stress which leads to calmer, healthier opossums.

Above are our two preferred types of enclosures. Critter nations are an all time favorite, but moms go in 50gal bins to keep babies safe (see below).
Prevue 528 small mammal cages are another good option.
Cage size
We recommend a minimum of ~4-6sqft. In a study comparing how STOs responded to different enclosures, STOs kept in a small enclosure were stressed. When moved to a larger, enriched enclosure, they acted naturally. The small cage was slightly bigger than a 20gal tank, the large was ~13sqft. We have found accessible enclosures in the middle that have, when set up well, eliminated stress behaviors (5-6sqft).
Bar spacing
.5 in or less for adults. Baby potatoes WILL ESCAPE ALL BARS. Until ~ 16weeks they need in a tank, bin or.25-.5in square mesh.. I've seen several cases where short-tailed opossums died when using 10gals. They are too easy to escape and one had their neck broken trying.

Bedding (pic soon)

We have to use fleece, I'm allergic to all other safe bedding. They need anti-pill or blizzard fleece. Other types of fabric or fleeces can catch fibers/strings on their toes. The inexpensive fleece throw blankets like the ones found at walmart aren't safe as bedding, but can be cut up and used as nesting material.

Other safe bedding:
Kiln dried pine
Aspen
Plain shredded paper (no ink)
Carefresh
Pellets (paper, aspen, grass)

Don't use:
Cedar-- it hurts everything with lungs. Not sure why its even sold for pets.
Corn cob-- it molds quickly
Clay or clay based litter-- too dusty

*I don't recommend dirt or coconut fiber. Bioactive enclosures can work for reptiles, but mammals wee and poo A LOT more. There's no fungus/bacteria/bug that can keep up with a mammal in limited space, but if you want to change that bedding weekly, go for it.

Hidden stitching (below) is much safer than stitching you can see (top pic with arrow pointing to it). They can lose toes or even limbs if the string gets caught on them (know of one case where a glider lost their penis that way).

Food and water dishes

We use bowls for both. We choose ceramic, but stainless steel is a good option too. We use the flat dishes for kibble, the mini crock dishes for water. They come in matching colors, but white dishes are easiest for us to check for debris . The mini dishes are for their "mash". We put crushed freeze dried insects and multi-vitamins in them and coat them with a little crested gecko food. Its a good way to make sure they get their vitamins, extra nutrition from insects, and can be used to get them used to new foods, by putting kibble in it too.

Water bottles can be dangerous. There is one water bottle, used for chicks, that is safe https://www.amazon.com/dp/B0197TZ03G/ref=cm_sw_r_cp_api_i_8P0EBS2ETKDF2RQXTR7T?fbclid=IwAR18mZxCRsVSwr0U_Fo-WjC3jsbDJjzA0gqNYGf8GE0hH2rtRtVUrMK2iko

Rodents have very strong front teeth. Their enamel (an outer layer of teeth), is reinforced with iron. Other species have much more fragile teeth and their front teeth (incisors) are tiny. Canines are also surprisingly weak. STOs, hedgehogs, and ferrets may try to bite at the metal and break their teeth.

Enrichment
Animals in captivity need to perform natural behaviors, not necessarily with natural items. It doesn't matter if its straw or fleece-- nesting is what's important; it doesn't matter if its wood or pvc pipe, climbing its what is important. A plastic wheel will do so much more than some branches. They don't give a darn if they are walking on dirt, just that they aren't getting sick from their bedding. We're not going for natural, just safe, easy to clean things that let them perform natural behaviors.

STOs need to build nests, run, climb, hide, and forage. The items blow help them act out those behaviors.

Wheels

Wheels are so necessary I'd consider them on par with housing and food. Between experience and (more importantly) understanding stress behaviors, I would say-- without exaggeration-- lacking an appropriate wheel is abuse.

With wheels, you're looking for a solid track, no side bars, and one big enough that their backs curve as little as possible. STOs may be the size of hamsters, but they need to deal with a tail and longer nose. This means thay need wheels bigger than you may expect. They also have dainty little feet and could hurt them running on mesh tracks.

We use 10in Carolina storm wheels for ladies and 12in kaytee comfort wheels for boys. These led to less of a back bend, though honestly they may do better with 15in chin spins. We will be adding some and I'll update with how it goes.

Sorry they're dark-- Hermes is our shiest and the most likely to hop quickly between wheels for me (great example for how nervous opossums rely on wheels to reduce stress).

Note how he has to run with is back higher up and more of a curve. A 10in would be a stretch for a hamster of the same size, but he has to prioritize keeping his nose straighter, sacrificing his back. Even keeping his head straighter than his back, his neck is still curved up.

Nests

Like wheels, nesting is a very important stress reducing behavior. Nests are going to be their favorite "toy". Provide lots of nesting material and many places to nest. The nesting material needs to be in strips to carry (examples below). Safe woods like aspen are a fine bedding, and they sure try to make something work, but they wont be able to nest effectively without some added material to carry.

They most likely nest in tree roots or on the ground in the wild. We provide hanging and ground nesting spots. Ours will nest in either, but lean towards ground nests.
A.) for those that use glider pouches, STO's don't nest in tree holes like gliders so I've found them used much more when placed on their sides.

For nesting material: we use cut up fleece (unlike for bedding, which needs anit-pill fleece, any fleece will do), paper towels, tissues, and toilet paper. Hay would also work, but I'm allergic. Make lots and just keep tossing it in there. Some like big nests.

Climbing

Many climbing toys also give them cover so they feel safe. Short-tailed opossums are terrestrial, but are very good climbers. My best guess is that its due to their diet. STO's in the wild eat a lot of insects like beetles and termites. These are going to be found on the ground, logs, and low branches. They like to run up and over things so we use tunnels and hammocks.
One reason I like critter nations is that they come with a built in climbing toy (their horizontal bars) and are easy to attach other toys to, but we've found ways to get climbing toys in bins.

We use:
-Hanging strips/screens (A) to make them feel safe. We make them ourselves
-Tiny hamster cages-- usually we get them used so no one can put hamsters in them (see examples in the pictures of enclosers above)
-hanging toys. For bins we use the mesh on the lids (its easier to run zip ties through the mesh and hang c-clips on the zip ties)
-Modified "pens" (3)

*Ropes and wood toys (2) are great, but they will ruin them-- males faster than ladies. Just keep note that you'll have to replace them from time to time.

**Going to experiment with PVC pipe covered in vet tape. I've seen them scale bare, vertical, 1in pvc pipe (it was Dotty-- she scaled a door frame once too)

Foraging toys

No offense to them, but they have pea sized brains. Their cerebral cortex (problem solving part of the brain) is smaller than that of other similar sized mammals. They are very food motivated, but not going to learn multi part tricks, such as do ___, with command ___ for treat (ex: chase tail to a verbal que). Instead use toys or tricks that are a direct line to food like following a laser or any foraging toys with parts they can push aside to the treat.

A near free (and favorite) foraging toy

This is my favorite way to feed live insects and the safest way if you're allergic to insects.

Each STO gets their own "bowl" when they are added to the passelry. We then put material in them and toss in insects.
We've used:
-Fleece (A). Strips can be any type of fleece.
-Paper towels (2)
-Toilet tissue (3)

*The latter two materials are great for allergies because you can toss the material out.
**Be careful with mealworms if you have a shellfish allergy (like me). It's not uncommon to react to both.

Toys

(new pics soon)
Occasionally I've seen them (usually babies) bite at straws(3) or move ground toys (A), but they don't get much out of them. They do like plastic rings like bracelets and will carry them with their tails.

I've harassed them with cat toy wands (4) that don't make any noise such as with feathers on the ends. Some like it, others.... don't.

Again, lots of nesting material (6) and sometimes I put it in balls (2)

Other supplies and examples

I recommend using a gram scale (can be found in kitchen supplies) to keep track of their weight.

Dotty is 95g, she just hopped on after I moved the container

I place them in a container to make it easier (at least for wiggly babies). I don't close the lid, but we put it at an angle on top to mitigate their hopping out