Taking Care of Orphaned Wild Opossums

Ron Hines DVM PhD 4/30/06

This is how the story usually begins. You stop along a roadside where a momma opossum has been killed. When you examine it closely, you find one or more babies still alive on her back or in her pouch! Or...You looked in your empty trash can this morning and there’s a little animal in it! At first you thought it was a rat – but it smiles back ! What should you do?

Furry opossums are quite easy to raise, if given the proper diet and care. Smaller infants are quite a challenge. Try to find a wildlife rehabilitator in your area with experience with very young opossums. Should you decide to attempt to raise the orphan(s) yourself, this is how I do it:
It’s unusual for us to get in babies that are not dehydrated to some extent. I like to begin by giving them subcutaneous fluids. Lactated ringers solution and appropriate sized syringes are available through my web page. I like to give them the fluid subcutaneous, that is under the skin of the lateral abdomen. I use a 3cc syringe with a 25-gauge needle. It is hard to tell you how much to give. It depends on the degree to which the skin fails to bounce back when you pinch it, the dryness of the mouth and depression of the eyes. Generally, you can give an amount roughly equal to the volume of their heads. Massage it around gently so it can be rapidly absorbed. I also use a hospital fluid called 5% Dextrose in lactated ringers injection. It comes in 250, 500 and 1,000 ml plastic pouches. In any case, once I’ve drawn from a pouch, I keep it in the refrigerator. Often I’ll add about 0.3ml of B-complex injectable vitamins to the fluid as well as about one quarter of a 1 gm vial of injectable ampicillin or cephalexin powder per liter of fluid because immature opossums that do not have the benefit of their mother’s milk are susceptible to many bacterial infections. There is rarely a need for the newer, high-powered antibiotics like Batryl because super-resistant hospital bacteria are unlikely to be present in wild opossums. I put the infants in a modified egg candler with a 40 watt light bulb in a small tin can (Home Depot will probably assemble an apparatus like this for you) – but you can use a heating pad under their container – just be sure not to cook them or let the container temperature rise over 94F! Chilled babies do not feed or digest well.

Typical orphan babies really need the fluids more than the nutrients at first. You can try to give it orally after you warm them up – LRS or diluted infant Pedialyte. It is always better to give small amounts quite frequently, than larger amounts less frequently. Feed them every two hours (if they don’t get bloated) until you run out of steam. About four percent of their body weight is a good amount. Take what they weigh in grams (there are 454grams per pound, 28grams/ounce) and multiply it by 0.04 and that’s the amount you give them in milliliters (ml), which is the same thing as cc.s. I like to use disposable 1ml lab pipettes. I think they are styrene. You can draw out the tip with a tweezers after you have heated it with a cigarette lighter, cut it and then flame-polish the end. I keep them in my shirt pocket during the day and feed them between clients.

Opossums that are cold, dehydrated and nearly dead when you get them often make miraculous recoveries with subcutaneous fluids. Giving fluids intravenously or intraperitoneally is a last ditch effort and is best left to a veterinarian if done at all. Only inject sterile saline (PSS), Ringer's solution or 5% dextrose solution.
Once its time to begin feeding them formula you have a dilemma. The bad news is that no three people feed baby opossums the same thing! The good news is that lots of these formulas work well. So don’t let anyone send you on a guilt trip because you added a drop of this or didn’t add a drop of that. Most Folks base their diets on powdered Multimilk, Nurtur-all, KMR, or Esbilac and rehabbers tend to be fiercely opinionated as to which one to choose, how to dilute it and what to add. I have had good success with all of them – I usually add vitamin E and antioxidants. I have not had good success with soya-based products for infants – but perhaps some of you have. I generally start dilute (ie one pt powder to three or even four parts distilled water) and gradually increase the concentration to one part powder to two parts water. I used to l mix up a cup of formula, pour it into ice cube trays and when frozen into Baggies. Then I thawed only what I need. But when you thaw it, the emulsified ingredients have clumped. I don’t know if this has any effect on its nutritional value but it looks distasteful, so now I only mix what I am about to use. A lot of rehabbers continue to add antibiotics throughout the young possums growing period. Others also give an anti-yeast product called Nystatin, available through my web page, but I have never felt the need to use it. As a general rule, the older they are, the less they need antibiotics. Some do well without any. I suggest you give them small periodic doses of the canine/feline formula of Bene Bac to maintain a health gastrointestinal flora with all the antibiotics rehabbers often used. When they are taking formula, pediatric amoxicillin or keflex is often given. I use 1mg/100grams of opossum but the doses vary widely. Luckily both are relatively low in toxicity if you go higher.

When you have a weak opossum baby or just lots and lots of them, tube feeding is an option. I use Silastic (silicone rubber) 18-gauge tubing on the end of an 18-gauge needle on a 1ml TB syringe – I can probably rig something up through my web page. A 2-3 inch 18 - 22 gauge intravenous catheter works well too but it is a bit stiffer and irritating to their tummies. GO SLOW! Be sure the milk flows smoothly and that you encounter no resistance. Begin with about 0.1ml so you and the baby get a feel for it. More baby wildlife are killed by overfeeding than underfeeding. I boil or microwave all utensils, mix my formulas just before I need them. The feeding syringes don’t generally melt in a microwave if they are covered with water. Throw them away when they don’t hold a vacuum any longer. Stimulate the baby’s bladders and bowel to evacuate with a warm damp pledget of cotton massaged over the vaginal-anal area.
Baby opossum feces are yellowish brown in color with the consistency and form of toothpaste. If it becomes watery and yellow-white you may be giving too much or the baby may have developed enteritis. Then dilute the formula, give it more frequently and you can give very small amounts of kaopectate until the stool is better formed. Greenish bilious stools are also abnormal. At these times, I will often crush a little Armour’s Pancreazime over the formula or food to “pre-digest” it.

As soon as I can, I introduce the babies to mashed foods: kitten chow, boiled egg, papaya, Gerber’s baby foods and mashed potato. Kitten chow is quite high in protein as is egg white, so I don’t let it constitute more than a quarter of their diet. Too high a protein content can have deleterious long-term effects on the kidneys. I add some NeoCalGlucon to their water or mashed food ingredients or sprinkle crushed calcium lactate tablets, vitamin E and antioxidants and omega 3&6 fatty acids over their food to help prevent metabolic bone disease which is a common problem. I have on occasion, used Vetamix brand Plex-Sol-C water-dispersible vitamins (in an amount similar what one would use to salt food) on the diet for 20 years. I don’t know if it is necessary but I continue to do so out of habit.

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