Opossums are solitary, reclusive animals that often are not understood or appreciated and the result can be traumatic and disastrous for them. Because they are basically defenseless, despite giving the appearance of being able to defend themselves, they have often been the target of unnecessary cruelty, especially in urban areas. A better knowledge and understanding of opossums and the benefits of having them as neighbors are essential to a peaceful coexistence. Listed below is some opossum information that may not be widely known.
Although they look like a big rat, the opossum is North America’s only marsupial and is related to the Kangaroo and Koala. A female gives birth twice a year, 13 days after conception, to 5 to 8 babies that remain in her pouch until able to walk around on their own by about 4 months of age. Baby opossums are so tiny at birth that 10 can fit in a teaspoon! The opossum’s long pink tail is prehensile, meaning it can be used as a fifth hand.
Opossums are exceptionally non-aggressive and non-destructive. They will not harm people or pets. However, they are wild animals and should not be handled. An opossum will use its 50 pointy teeth to defend itself if necessary.
Opossums do not dig into the soil nor do they destroy property.
Opossums help maintain a clean and healthy environment. They eat all types of insects including cockroaches, crickets, beetles, etc. They catch and eat rats and mice. They consume dead animals of all types. They like overripe fruit, berries, and grapes that have fallen to the ground and they think that snails and slugs are a delicacy. They are one of the few animals that regularly prey on shrews and moles. They are known as “Nature’s Little Sanitation Engineers!”
In general, opossums present a far lower health risk to humans than dogs and cats. They have a naturally high level of immunity to diseases. Opossums are more resistant to rabies than any other mammal. They can carry fleas and will bite if provoked.
Learning and discrimination tests rank opossums above dogs in intelligence and more on the level of pigs.
Opossums are transient staying only 2-3 days in an area before moving on. They do not have a territory but are always on the move, going to wherever the food is. Females stay in a smaller area while they care for their young. Their dens are located in a variety of areas including stumps, vine tangles, attics, garages, and hollow trees, rock piles, under buildings and in the abandoned burrows of other animals.
If attacked and unable to fight or run from danger it puts up a terrific bluff and can give the appearance of being really good at defending itself. As a last resort, it will collapse and play dead. This involuntary response causes the opossum to become comatose for a period of from 40 minutes to 4 hours. Give a “dead” opossum the benefit of the doubt and do not dispose of the body until you are sure it is dead.
Few opossums survive to become adults and those that do have a life expectancy of from only one to two years due to their many predators, man is the worst.
If there is an opossum in your area, just leave her alone, she should move on in a couple of days. However, if you find an opossum continues to return to your area, try eliminating the things that are attracting him:
Do not leave pet food out at night. Clear away bushes, woodpiles, and other hiding places.
Do not leave garage doors open at night.
If an opossum gets into your house or garage, she can be safely trapped by leaning an empty, tall kitchen trash can at a 30-45 degree angle against something the opossum can climb onto. Place cat food or ripe fruit at the bottom of the trash can. The opossum will be able to climb into the trash can but will not be able to get out. Immediately take the can outside. Tip the can on its side and the opossum will leave when it feels it is safe. You can also try to leave a trail of cat food leading to an open door. Observe quietly at a distance. Once he leaves, shut the door. Do not try to push the opossum out with a broom. The frightened animal will freeze and not move.
If there is an opossum in your yard, leave him alone. If she is in your garden, she is helping you by eating the harmful pests that do damage.
If you find an injured or orphaned opossum, contact the State Department of Environmental Conservation for assistance. Ask for a referral to a wildlife rehabber who will humanely capture and relocate your visitor. Be aware that they may refer you to an exterminator which in many cases will result in the death of the opossum. Municipal Animal Control Agencies often euthanize wild animals also.
If you find a baby opossum, keep in mind that where there is one orphan, there may be more. Be very quiet and listen for the “sneezing” sounds the young make to call the mother. Don’t try to care for the animals yourself. Unless you are a trained wildlife rehabilitator, you could do more harm than good if you don’t know what you are doing. If the baby is at least 7 inches from nose to rump, he can survive on his own and should be left alone.
For more information, contact the National Opossum Society P.O. Box 21197 Catonsville, MD 21228
10 things you didn’t know about opossums By Melissa Breyer
Pity the poor opossum. The oft-maligned marsupial definitely suffers from an image problem — it is frequently perceived more as a giant, dirty, scavenging rat rather than a cute creature of the wild. But whether you love them or hate them, North America’s only marsupial has a set of unique characteristics that might transform aversion into affection.
But first, the burning question: is it opossum or possum? In 1608, Capt. John Smith coined the word opossum from the word “opossum,” the Algonquian term meaning “white animal.” In his notes, the captain wrote: “An Opossum hath an head like a Swine, and a tail like a Rat, and is of the bignes of a Cat. Under her belly she hath a bagge, wherein shee lodgeth, carrieth, and sucketh her young.”
No one is quite sure how the opossum’s “o” was dropped, but it appeared in print as “possum” as early as 1613, and remains the colloquial term in many regions of the country. However, there are true possums – just not in the North American neck of the woods. Possums include any of several species (from the family Phalangeridae) of nocturnal, arboreal marsupials of Australia and New Guinea, and were mistakenly named in the 18th century when the naturalist from Capt. James Cook’s expedition wrongly called them possums after their North American cousins. Nonetheless, it’s the Australian ones that hold the true scientific title of “possum” now.
- Natural immunity. Opossums are mostly immune to rabies, and in fact, they are eight times less likely to carry rabies compared to wild dogs.
- Poison control. Opossums have superpowers against snakes. They have partial or total immunity to the venom produced by rattlesnakes, cottonmouths, and other pit vipers.
- Omnivores galore. Their normal diet consists of carrion, rodents, insects, snails, slugs, birds, eggs, frogs, plants, fruits and grains. They also eat human food, table scraps, dog food and cat food. They have an unusually high need for calcium, which incites them to eat the skeletons of rodents and road kill they consume. They’re the sanitation workers of the wild.
- Smart critters. Although many people think opossums are not the sharpest knives in the drawer, there are several areas of intelligence in which they soar. For one, they have a remarkable ability to find food and to remember where it is. When tested for the ability to remember where food is, opossums scored better than rats, rabbits, cats, dogs but not as well as humans. They also can find their way through a maze more quickly than rats and cats.
- Pest control. Since their diet allows them to indulge on snails, slugs, and beetles, they are a welcome addition to the garden. Opossums also keep rats and cockroaches at bay by competing with them for food. In fact, it’s common for opossums to kill cockroaches and rats if they find them in their territory.
- All thumbs. The opossum has opposable “thumbs.” The opossum’s “thumbs” (called halux) are on its rear feet (so, technically they’re toes), and abet the opossum’s formidable climbing skills. Primates and opossums are the only mammals with opposable first toes.
- Impressive tails. They have prehensile tails which are adapted for grasping and wrapping around things like tree limbs. The opossum can hang from its tail for short periods of time, but the creature doesn’t sleep hanging from its tail, as some people think. Opossums have been observed carrying bundles of grasses and other materials by looping their tail around them; this conscious control leads many to consider the tail as a fifth appendage, like a hand.
- Good pupils. The eyes of the opossum appear black, but what we are seeing are strongly dilated pupil; there is iris around them, it’s just mostly out of sight. The giant pupils are thought to be an adaptation to their nocturnal habits.
- Smile! The mouth of an opossum holds an impressive 50 teeth.
- Natural Defenses. When threatened, opossums run, growl, belch, urinate and defecate. And when all else fails, they “play ‘possum” and act as if they are dead. It is an involuntary response (like fainting) rather than a conscious act. They roll over, become stiff, close their eyes (or stare off into space) and bare their teeth as saliva foams around the mouth and a foul-smelling fluid is secreted from glands. The catatonic state can last for up to four hours and has proven effective as a deterrent to predators looking for a hot meal.
And a bonus for the Scrabble players: Male opossums are called jacks and females are called jills. The young are referred to as joeys, just like their Australian cousins, and a group of opossums is called a passel.
Frequently Asked Questions
Is a possum and an opossum the same thing?
Yes and no. Throughout America, the opossum is often referred to colloquially as a possum (similarly to the way some people refer to a potato as a tater or to a mosquito as a skeeter), but its actual name is opossum. When we refer to it by its colloquial name on this website, we usually add an apostrophe at the beginning to indicate the omission of the initial o: ’possum. But there really is an animal called a possum (without an initial o) that differs significantly from the North American opossum. The true possum is indigenous to Australia and looks quite unlike the American variety. You can see pictures of the Australian possum here and there are also links to other possum websites.
What do opossums eat?
Opossums are not picky eaters and will consume almost anything, including table scraps and carrion. They do seem to have a particular fondness for cat food, however, especially the tinned varieties. Their normal diet consists of carrion, rodents, insects, frogs, and plants including fruits and grains.
How big can an opossum get?
Most are about the size of a large house cat, from 15 to 20 inches long. They generally weigh 10 to 13 pounds. This can vary, however, just as height and weight vary among humans. Some well-fed opossums can seem gargantuan, especially when they startle you on an evening walk.
Are opossums dangerous to pets?
Opossums will sometimes try to eat small critters such as mice, reptiles, amphibians, and even young kittens if other food is scarce. They will leave larger animals alone and, in fact, are more likely to be harmed by a dog or full-grown cat than they are to inflict injury on them. They will rarely fight, despite putting up a fearsome display if threatened, and most likely will simply attempt to flee or play dead.
The only animals that should avoid exposure to opossums are birds, horses, and sea otters. Strange as that may sound if these animals ingest opossum feces they are at high risk of contracting a deadly disease known as sarcocystosis. If you suspect an opossum may have entered a stable of horses, look for signs of their feces.
Fish have been disappearing from my pond. Is an opossum responsible? No, the opossum is not catching your fish, Opossums are rather lazy and will always seek out readily available food whenever possible. It is not generally industrious enough to catch fish or try to attack an animal that might fight back. The disappearance of fish or chickens is more likely due to a raccoon, fox, or badger. If you see an opossum eating your fish, most likely it came across the remains that another creature left behind on the bank.
Lately, I have seen several holes in my yard. Is this the work of opossums?
No, opossums do not dig. They will often inhabit holes that were created by other animals, but they are themselves not miners. If you have holes in your yard, keep a lookout for armadillos, moles, groundhogs, or other digger critters.
I live in a large city. Was that really an opossum I saw in my dumpster?
It could well have been an opossum. Opossums have not restricted their range to rural areas and more and more can be found in densely populated urban environments. (I have even received reports of sightings from Brooklyn and Toronto.)
Last night I saw an opossum on top of a high fence. Can they jump or climb?
They cannot jump, but they are superb climbers. One should never hope to keep an opossum out of a yard with a mere fence. With their opposable thumbs and prehensile tail, they can scale practically any obstacle.
Opossums are nocturnal, but I saw one out during daylight. Is this normal?
Opossums are generally nocturnal, foraging throughout the night. But it is not at all unusual to see an opossum out during the daytime, especially during cold weather. They also can be seen in the day when food is scarce or when they have been disturbed from their sleeping quarters. The winter months will see many opossums change their foraging habits from night to day in order to try to take advantage of the warmer weather during sunlight hours.
Do opossums carry rabies?
Unlike most wild animals, opossums are highly resistant to rabies. It is extremely rare to encounter a rabid opossum, though if bitten or scratched by one, it is nevertheless advisable to see a physician immediately. Any opossum that would behave in such an uncharacteristic fashion must be assumed to be rabid.
Are opossums immune to the bite of rattlesnakes and copperheads?
Yes, they are highly resistant to snakebite, probably due to their low body temperature and metabolic rate.
What are male and female opossums called?
Male opossums are called jacks, and females are called jills. (Sound familiar?) The young are referred to as joeys, just like their Australian cousins. A group of opossums is called a passel.
What kinds of noises does an opossum make?
Opossums are very quiet creatures. You are far more likely to see one long before hearing any noises from it. When threatened they often will hiss, much like a cat, and can make a low growling sound. Some have reported hearing opossums softly purring to their young, though I have never been so privileged. One person wrote me to say they’d once heard a young opossum mewing like a kitten, but it is the only such report I’ve received.
How many babies does an opossum have in each litter?
As with most mammals, the number will vary, but generally, opossums will give birth to between 6-25 young one to three times a year, usually between January and July. Most litters consist of 6 to 9 young. Of these no more than 13 will survive because the mother only has 13 teats with which to feed them. Each joey will latch onto a teat, and those who do not secure a place in their mother’s pouch will starve and die.
Do opossums really mate through the nose?
This is a myth that has been around for ages and has become so prevalent that I actually have seen a few websites about opossums which state it as fact. The truth is, there is no truth to it. The whole crazy idea seems to have come about because the male opossum has a bifid (forked) penis, and the only corresponding parts on the female appeared to be the nostrils. The myth states that after mating through the nose, the female later sneezes the tiny fetuses into her pouch. Rather than indicating what a unique animal the opossum is, this story actually just reveals how bizarre some people are in what they can imagine! In reality, the male has a bifid penis because the female has two uteri (wombs), and sperm is deposited into each womb during copulation. But mating occurs through the vagina, not through the nose.
I have heard that opossums are deaf and/or blind. Is this true?
No. Neither their eyesight nor their hearing is particularly acute, but they can both see and hear.
What should I do with an injured opossum?
The best thing to do is to call a local veterinarian or animal control officer. Although opossums are rarely aggressive, any injured animal that is in pain may react unpredictably and should not be handled except by an expert.
What should I do with an orphaned baby opossum? (If the baby is 7 inches from nose to tail it can live on its own.)
Again, it is best to consult with a local veterinarian or animal control officer for assistance. Also, try to locate a rehabber in your area with experience in caring for orphaned animals. If you need to do the rehabbing yourself and aren’t sure what to do, find a rehabber in your area by going to the following directories:
Wildlife Rehabbers by State (Letters A-M) Wildlife Rehabbers by State (Letters N-W) If you are unable to locate a rehabber from the above directories, try contacting one of the following experienced rehabbers who belong to the Imperial Order of the Opossum:
- Andy (Texas)• Lorna Buffum (Rhode Island)• Laura Burdett (Texas)• Marie Calford (Canada)• SugarBane (Tennessee)
Also, check with your local library to see if they have the book I Found a Baby Opossum, What Do I Do? By Dale Bick Carlson. If they don’t have it, they can probably get it for you through an interlibrary loan. You also can find copies by going to BookFinder.com. Though out of print, it is an excellent resource for those who wish to rehab an orphaned opossum.
How do I relocate a bothersome opossum?
First of all, it is never necessary to kill the animal. The kindest way to remove an opossum is to set a Have-A-Heart trap baited with tinned cat food. These are harmless traps that can be obtained at many hardware or farm supply stores or from some rent-all establishments. Once the opossum has been captured, it can be taken to a remote area and released. Even this is generally not necessary, however, because opossums are transient animals, usually staying in a particular area only a few days at a time and then moving on. The best way to avoid being “bothered” by an opossum is simply to make sure no food is available to them. Don’t leave out pet food or table scraps and make sure your trash cans are fully closed. With no food available in your yard, they will simply go search elsewhere.
An opossum got in my house through the back door. How do I remove it?
If there is no time to call animal control, You can throw a blanket over him and take outside you may be able to coax it out with a broom. Try to avoid hurting the animal, but simply attempt just to urge him along. Sometimes they can become quite stubborn and hide under a table or couch, looking very fearsome by baring their 50 teeth. I once removed an opossum from a neighbor’s house by cautiously picking it up by the tail (do not pull their tail), but I did have on heavy gloves. Opossums usually will not bite, but they certainly can if given the opportunity. It is difficult for them when held by the tail to curl back enough to reach the holder’s hand, but this is not a method I would recommend for a novice. If possible, leave the door open awhile, perhaps with some cat food just outside the threshold, and wait to see if he leaves on his own. If it is cold out, you may have a long wait. An animal control officer is your best bet if you are anxious for him to depart.
Do opossums make good pets?
Generally speaking, no but there are exceptions. Animals are like people in that no two are alike. Some people have kept opossums as pets and enjoyed their company very much. Usually the best pets are those rescued when very young. A full-grown opossum will rarely adapt well to captivity. As a rule, however, keeping opossums as pets is not recommended. You also should check your local and state or provincial laws to be sure whether it is legal to do so in your area before attempting this.
How far north do opossums range? The range of the opossum seems to be ever expanding. They can be found in almost every state in the U.S. (excepting some of the arid regions), portions of Mexico, and in several Canadian provinces (including as far north as Toronto). They also inhabit urban as well as rural areas. It would appear that their capacity for expansion is almost limitless.
What are the natural predators of opossums?
Many animals happily ignore the gentle opossum, and there have been many reports of pet cats making friends with neighborhood opossums. Their natural enemies, though, are foxes, coyotes, dogs, bobcats, and owls. But even more than these natural predators, their greatest enemy in the modern world is the automobile.
Do opossums hibernate during winter?
Opossums do not hibernate. Their greatest challenge during winter, especially in colder climates, is simply to survive. Very often opossums will alter their foraging habits during winter, coming out during the day when it is warmer rather than at night. It is not uncommon for opossums in northern regions to suffer frostbite during extremely cold periods. Their tails are particularly susceptible to frostbite as they have no fur covering to protect them. Sometimes opossums can be found relocating to basements or garages in order to escape the cold. The only way to prevent this is to make sure all openings are fully covered.
On a side note; I was fortunate enough to care for one of these beautiful little creatures when the mother of 2 babies was killed and the babies were ill; when they were brought back to health they were too tame to be released into the wild so I took one and an educational program called Inside the Outdoors took the other. Tallulah was what we named her and she lived with me and my son for 3 wonderful years. Normally it is against the law to keep wild animals I was given special permission to raise her because of her non-releasable status. This is a link to her photo album Talluah Jean Possum
One big reason for the general public to not keep an opossum is that the wrong diet can kill an opossum the opossum diet is very specific and important if fed wrong they can and will develop metabolic bone disease:
PLEASE READ THIS!
Achieving good nutrition in the opossum is a difficult and evolving task. This challenging aspect of opossum care is one of the reasons that diets recommended by various groups and individuals can be so diverse, and some so detrimental. The opossum as a biological organism is not forgiving of a poor diet- they WILL get sick, lose mobility, or die if they are fed inappropriately.
The Modified Jurgelski- Don’t Do It.
Various sources have advised to feed what is known as the Modified Jurgelski Diet (90% kitten chow and 10% raw beef liver) to juvenile opossums. It is our experience that this diet, or any diet which includes any meat or protein products except in very restricted amounts, or has an excessive amount of Vitamin A or D, as is found in beef liver, is a dangerous diet for the omnivorous opossum. Even Dr. Jurgelski didn’t believe the diet he developed for laboratory opossums was adequate (references available). It is our hope that the MJD will soon be seen as so outdated that this advisory will become unnecessary.
We see many cases of Metabolic Bone Disease (nutritional secondary hyperparathyroidism) in opossums that have been fed poor diets. MBD can progress to cause immobility and death, if not corrected quickly and appropriately! It is not a matter of IF the opossum will become ill, it is a matter of when!
The MJ diet is not the only harmful diet being promoted by various groups and individuals AND websites. These assorted diets may be based on canned cat or dog food, chicken meat, eggs, kitten chow, or include excessive amounts of applesauce, human baby cereals, etc. DO NOT USE THEM!
An important note regarding infant opossum formula: we are seeing increasing numbers of cases where infants fed “name brand” formula is resulting in hypocalcemic episodes. Untreated hypocalcemia can quickly result in death in infant opossums! Remember that a photo of an opossum on a label does NOT qualify it as a suitable milk replacer.
Current diet information, including the pathogenesis of MBD, is available with membership in the National Opossum Society. It is against N.O.S. policy to publish complete diet plans or infant formula on its website or to have others publish it electronically. In our experience, it is essential that anyone trying to provide care for any opossum be in telephone or face-to-face contact with an experienced opossum rehabilitator. This is ESPECIALLY true if you are trying to correct MBD. Therefore, we ask that you establish this contact with a call to your local experienced opossum rehabilitators and veterinarians. You will find that the N.O.S. membership packet is filled with valuable information about the welfare of opossums, and phone numbers for experienced rehabilitators.
What Do They Eat in the Wild??
The diet that the National Opossum Society recommends is based on several studies wherein the stomach contents of wild opossums were analyzed. All studies show variation in diet according to season and habitat.
The following table is drawn from one of those studies, published in The Murrelet, Spring 1980, authored by David D. Hopkins and Richard B. Forbes. The study was performed on road-killed opossums in and near Portland, Oregon.
mammals 27% leaf litter 11% fruits, seed, bulbs, etc. 10% gastropods 10% garbage 9% earthworms 9% pet food 9% grass, green leaves 8% insects 3% birds 3% misc. animal tissue 1%
Another study conducted in New York State in 1951 analyzed the stomach contents of 187 opossums. The study was conducted by W.J. Hamilton, Jr. and published The Journal of Wildlife Management, Vol. 15, No. 3
Fruit 18.0% Amphibia 17.2% Mammals 14.2% Insects 13.4% Grasses 6.6% Worms 5.4% Reptiles 5.3% Birds 5.0% Carrion 4.8% misc. or Undetermined 6.7% PLEASE NOTE THAT THIS IS NOT A DIET RECOMMENDATION! THESE STUDIES ARE EXAMPLES OF THE EXTREME DIVERSITY OF THE OPOSSUM’S NATURAL DIET — ONE WE MUST STRIVE TO MIMIC WHEN WE HAVE THEM IN OUR CARE!!
Check out the nutrient content in the foods that you are feeding at the USDA Nutrient Database
For current diet information, please contact the National Opossum Society.
NUTRITIONAL METABOLIC BONE DISEASE: Its Causes . . . Its Cure
By: A. M. Henness, D.V.M., NOS Veterinary Advisor © 1996. This Web article contains minor edits for clarity.
Introduction and Background
Numerous groups and wildlife facilities, as well as individual rehabilitators, have used (or are using) some form of the Modified Jurgelski Diet for opossums (90% kitten chow: 10% raw beef liver). Many use it innocently thinking it is safe and appropriate. IT IS NEITHER!
Before I dropped the other opossum group I founded, I carefully explained why their leadership’s planned use of this and similar diets was extremely ill-advised; why it was guaranteed to harm, perhaps kill, opossums of any age (i.e., they were given basic principles of general nutrition). Nonetheless, these women embraced the diet and have touted it widely. This includes (recently) on the Internet and a video and handbook which direct the user to start this diet on infants of 80-100 grams body weight. Consequently, MANY opossums are NOW BEING DAMAGED IN GREATER NUMBERS (see letter to Editor, ‘Possum Tales, Vol. 10, No. 2-3, July 1996). Ironically, caregivers strictly following the MJ diet (from 80 grams) are seeing the most rapid onset of dramatic signs of Nutritional Metabolic Bone Disease (NMBD); whereas, caregivers still providing at least some fruit and vegetables, or those who give it to older opossums, are seeing delayed onset of overt signs of NMBD. These latter opossums are often more severely affected by skeletal and systemic complications due to their longer duration on this diet. In contrast, the diet NOS recommends will not cause NMBD when used exactly as published. However, if its user “improvises” usually with protein (fish, chicken, etc.) far in excess of that recommended problems can and do occur (see letter to Editor, Vol. 10, No. 1, “Possum Tales, January 1996).
- ANY DIET, when used in specific, INCORRECT ways, can cause NMBD!!
- CERTAIN DIETS will cause NMBD EVERY TIME, regardless of usage.
This report and a companion one on details of portion quantities in NOS-recommended diets (see “Possum Tales, Vol. 10, No. 2-3, July, 1996) discuss these issues in an effort to provide clarification. This is not intended to be an all-inclusive treatise on NMBD, but it contains the basics to more fully comprehend the nature of the problem with improperly balanced diets. I sincerely hope all our reader’s veterinarians, rehabilitators, orphan caregivers, pet guardians, and wildlife appreciators will read that which follows . . . then USE THE INFORMATION! Use it in discussions with others, share it on The Net and in letters to friends and those caring for opossums. Each of us as opossum ambassadors has the responsibility to get involved! Eventually, enough people will have the CORRECT information; this will serve as a buffer against the continued spread of this scourge to opossums’ bodies and lives . . . rather like a wide-spread vaccination program which ultimately stops an epidemic. For NMBD is becoming a nation-wide epidemic from the MJD and similarly unbalanced diets.
The Metabolic Bone Disease Complex: Metabolic bone disease (“MBD”) is the term for an entire group of diseases which occur as a result of: (1) defective bone formation, (2) excessive bone resorption, or (3) some combination of the two. Defective formation, in its “pure” form, is either osteoporosis (insufficient bone formation) or rickets/osteomalacia (defect in mineralization of bone). Excessive resorption, in its “pure” form, results from too much osteolysis (bone breakdown at the cellular level).In their least complicated presentations, MBD is classified as one of the following disorders (NOTE: in “real life” one frequently sees combinations):
- Nutritional secondary hyperparathyroidism, caused by intake of low calcium: high phosphorous foods (i.e., protein in excess); ratios of calcium: phosphorus can reach 1:16 or greater! Most mammals require their diets to have a ratio of 1.0:1.0 to 1.2:1.0. Low calcium intake leads to a fall in blood calcium; this activates parathyroid hormone, which, in turn, stimulates demineralization of bone and release of calcium to maintain blood levels. This is independent of Vitamin D. The activation of the parathyroid hormone also increases urinary calcium loss.
- Rickets (in young) or osteomalacia (in adult) is rare, due to widespread availability of Vitamin D in food. Vitamin D deficiency will lead to low calcium: low phosphorus, because of reduced calcium absorption by and use in the body. Vitamin D works best when ingested with Vitamin A. But excesses in A or D can cause functional deficiency in the other (though it may be at adequate levels).
- Renal osteodystrophy – accelerated calcium loss from the bones and out via kidneys, due to insufficiency or failure of these organs. Can be temporary (e.g. as a result of medication or certain vitamins), or progressive (e.g. in renal disease).
- Hypervitaminosis A osteopathy – Depending on the degree or chonicity of excessive Vitamin A intake, it causes varying amounts of increased bone deposition or accelerates calcium loss from bones and from the body.
Origination and Development of Clinical Metabolic Bone Disease (“MBD”): The precise circumstances which lead to MBD usually vary from one facility or individual to another. For, although its development involves inappropriate levels of ONE OR MORE of the following, no two situations are exactly the same:
- Protein in excess (calcium: phosphorus ratio is too low, sometimes dramatically so!).
- Vitamin A (deficiency or excess).
- Vitamin D (deficiency or excess).
- A variety of possible, though less frequently seen, problems. One example is an incident wherein an Amoxicillin overdose caused temporary renal dysfunction with resulting accelerated loss of urinary calcium.
Vitamin A or D Deficiency as a Cause of NMBD: “Pure” deficiencies of Vitamins A or D are essentially non-existent in orphan care. Infant wildlife formulas all contain some form of these nutrients in sufficient quantities to augment the orphan’s own body stores. Some formula mixes actually contain very high levels which can lead to MBD (see below).In the late infant juvenile period, prior to release, “pure” deficiency of Vitamin A or D can theoretically occur. But most diets fed opossums in captivity prior to release are rarely deficient in either vitamin due to wide-spread fortification in commercial chows. Although they are lower in A than opossums appear to require (NOTE: cat chow is higher in Vitamin A than are dog chows), they are usually sufficient to augment whatever body stores remain until they are released . . . but only if they are not fed protein in excess! Appropriate deworming with levamisole by injection removes the potential drain of vitamins and nutrients by parasites. NOTE: Actually, excess Vitamin A is a greater potential danger; it is involved in MBD caused by the “MJD” or similar diets (see below)! Deficiency of one or both vitamins may be present in adult opossums having the so-called “emaciation syndrome”, where cachexia (malnutrition, wasting), parasitism and prolonged nutritional deprivation is frequently associated with states of systemic infection, trauma, etc. In these cases, body muscle, organ mass and fat depot sites are reduced. Vitamin A and D stores are reduced or near absent, too. It is uncommon to find clinical evidence of bone density loss of any significance, however, unless there is associated renal insufficiency (see renal osteodystrophy discussion). Most of these animals were they not treated appropriately would die of all their other problems long before fractures or other bone damage might occur. A proper and balanced diet is of extreme importance, of course, for recovery of these animals. Vitamin D deficiency leads to rickets. It is seldom recognized now in human populations in developed countries unless nutrition is inadequate and the individual receives no sunlight (the best means to our bodies of forming Vitamin D). Although opossums in infancy may be exposed to some sunlight, they seldom are for the bulk of their lives. Their primary source of this vitamin is their food predominantly from insects, slugs, snails, mammals, etc., which comprise approximately 70% of their diet. A slightly analogous situation exists in humans: The more pigment in one’s skin the longer exposure to sun is required to form adequate levels of Vitamin D; dietary sources can play a vital role in these circumstances. Calcium: Phosphorus Ratio less than Minimum of 1:1 as a Cause ofNMBD: Many foods, in addition to beef, chicken, fish, eggs, or organ meats, contain protein. Even vegetables! The difference is, the calcium: phosphorus ratio is usually better (i.e. closer to the desired ratio) in vegetables and, of course, dairy foods, than it is in “pure protein” foods. Additionally, not all proteins are “created equal”. For example, organ meats and mackerel have a much lower ratio than do sardine, salmon or chicken, and are also disproportionately higher in Vitamin A and D. One must examine more than a few constituents of the foods we feed to fully assess their suitability. Vitamin A and/or D in EXCESS as a Cause ofNMBD: Paradoxically, these vitamins . . . which, in deficiency, can lead to bone calcium loss, weakened and fractured bones, mobility problems, septicemic illness via organ damage and pain . . . these vitamins in EXCESS will also lead to these same problems and often far worse organ damage! It may also happen more quickly than with other possible causes ofNMBD. Vitamin A, in excess, increases osteoclast (cells which resorb bone) activity. This leads to hypercalcemia (overload of calcium in the bloodstream) and, initially, more bone formation (possibly fusion) along certain joints and the spine. It also damages renal tubules which, if it continues, causes excessive calcium excretion and, ultimately, hypocalcemia (shortage of calcium in the bloodstream). The animal experiences deep bone pain, has flaky, dry skin, a poor appetite, nausea, and diarrhea. The liver may be enlarged; there is often excessive urine output. Discontinuing the vitamin will usually reverse all signs within days. But, bone damage may or may not be fully reversible, depending upon the presence and degree of deformities. Vitamin D in excess is the most toxic vitamin. It, too, increases osteoclast activity, and causes hypercalcemia and urinary calcium excretion. Additionally, it leads to calcium deposition in heart and skeletal muscles, artery walls and the lungs. The animal is anorexic, nauseated, and may vomit. Continued excess may cause hypertension and severe kidney damage from calcium deposition in the tubules. Discontinuation of excess Vitamin D results in quick recovery from all signs, except for any deformities in bone. Only time, a properly balanced diet, and a planned exercise program will enhance recovery and assist the patient in remodeling damaged bones.
Calcium Supplementation: Calcium supplementation in the opossum should be limited to high calcium food sources in controlled amounts for a restricted length of time. NO PURE calcium supplements should be used, EXCEPT in severe causes of NMBD for only the first few days of treatment. There is NO ADVANTAGE to continuing “pure” calcium supplements; the opossum is extremely efficient at absorbing and utilizing dietary calcium from a BALANCED diet. Supplements can lead to hypercalcemia, depressing of osteoclast activity, and depression of bone and cartilage remodeling and maturation. In other words: TOO MUCH OF A “GOOD THING” even calcium! CAN IMPAIR DEVELOPMENT AND REMODELING OF BONE! Typical Sequence of Signs, According to Degree or Duration of NMBD: Once signs of NMBD are recognized, regardless of the duration or extent, ONE MUST IMMEDIATELY STOP THE DIET AND/OR SUPPLEMENTS OF ANY TYPE. One must institute an appropriate diet, deficient in protein, in a planned management program! Consultation with someone experienced in care of these patients is STRONGLY URGED, so that recover can be as uncomplicated and as complete as the animal is able to achieve. DO NOT DELAY! 1. (days to two weeks, approximately, from start of cause):
a. Usually limited to infants and young juveniles (up to approximately 1 lb. body weight).
b. Hypocalcemia may be the first sign (hyperactive behavior, tremors, inappropriate fear, sometimes inappropriate jaw snapping, twitching. (Some of these signs might be confused with the opossum that is in need of levamisole).c. Other signs will progress, as below, if cause is not removed/corrected immediately. NOTE: THIS IS ONE CAUSE OF SO-CALLED CANNIBALISM. These animals will attack anything, including littermates or cage mates. This is not true cannibalism; but can maim or kill others, REGARDLESS! You will only see this in human-fed infants.2. Acute chronic (days to weeks to months):a. Can occur at any age through adulthood; but always sooner and often more extensive in young, rapid-growing animal.b. Sequence from earliest (mild NMBD) to advanced (severe and/or chronic NMBD): (1) Slight to significant depressed grip in hands/feet and in strength of limbs or tail; reluctant to climb.(2) Depressed activity level. Tends to sleep more; cranky when awake; will not run when active. (Pain begins here.)(3) Appetite may begin to change; grip markedly reduced.(4) Stands with restricted stance; walks with short mincing steps, variously described as “walking on eggshells.” Can’t climb. (Pain increases.)(5) Early signs of systemic changes (e.g. urinary output may rise, dilute urine, sometimes increased water intake).(6) Limbs appear to have become stocky or chubby; palpation (examining by touching) of the long bones causes significant pain. Changes are due to thinning of the cortex (outer portion of the bone) while the diameter of the limb widens.(7) If blood calcium is fluctuating, may see tremors and jerky movements. Or blood level may be normal and phosphorus may be elevated.(8) Fractures are possibility at any time from 5 or 6 above digits first, then long bones, spine, etc.(9) Walks in crouched posture with creeping movements of limbs; down on elbows and/or knees and ankles; hands and feet have abnormal postures with little use.(10) Distortion of limbs, loss of appetite, further changes in urine and bowel habits.(11) Skull changes, including, but not limited to, inability to effectively use mouth/jaw parts; bulging of eyes, etc.(12) Depending on the severity of the diet, site of fractures (e.g. thoracic (chest) area has potential for extremely grave prognosis), age of animal, and other problems (e.g. parasites, infection, etc.), the animal is ill enough to die at any point if intervention is not immediate and aggressive. : It is
always worth treating and rehabilitating these opossums to whatever level of functional recovery they may attain particularly since WE caused this animal’s distress and pain, regardless of how sincere our intentions were to help. WE must accept responsibility, correct the problem, and assist this patient back to health. Recovery takes at least as long to accomplish as did the damage to occur. Complications or residual problems can arise; but their extent is unknown until one reaches the late recovery phase of rehabilitation. If the disorder is recognized early and halted, opossums will completely recover! The most severely affected opossums can still live quite happy, comfortable lives in captivity — as pets, or in education programs. As has been pointed out in prior articles, mobility impairment results in the need to MONITOR CLOSELY FOR UTI (urinary tract infections) . . . for life. A female must have ovario-vaginal-hysterectomy as soon as she is in recovery and otherwise healthy (see ‘Possum Tales, Vol. 8, No.1-2, 1994 articles on female anatomy and genital tract infections). Comments on the Jurgelski , or Similar Diets, in View of Tabulated Data Provided in Table 1 and Discussion Above: Although Table 1 only includes major components of the foods listed, one must not make the assumption these are their only important constituents (see note with Table ). One ordinarily begins evaluation of any given diet by examining these values; either in relation to another diet or as compared with what one knows of the species’ requirements. But, more extensive analysis is necessary to ascertain precise dietary needs of any given species. Unfortunately, this would dictate an EXPERIMENTAL STUDY which, by its very nature, leads to detriment (sometimes illness and death) of many subjects in the study in this case, opossums. For we do not know their full dietary requirements! We only know a few of the extremes (i.e., too much or too little of something causes a specific problem), and data from post mortem examination of stomach and intestinal contents of urban opossums in two separate studies (see reading list at end).I believe the “experiment” of the MJD diet for opossums has failed! It has harmed more than it has helped; and it has especially done so at their most vulnerable point in life: the rapid-growth months. And, when it is given EVEN FOR A FEW DAYS! Just prior to release, one ensures damaged and at-risk animals are in the environment . . . because the care-giver is apparently incapable of recognizing the subtle signs of VERY EARLY NMBD! These just-released 200-gram plus opossums are prey to any animal that comes upon them. In pain, weak, unable to run or climb, they are caught, injured or killed. Guilt can be a powerful motivator to effect positive change in our behavior . . . if we acknowledge it, instead of denying it or misdirecting it elsewhere. Please note, from Table 1, that kitten chow: raw beef liver APPEARS to have a “wonderful” calcium: phosphorus ratio. For the “MJD” diet, hypervitaminosis A (over-dose of Vitamin A) is of FAR GREATER SIGNIFICANCE, and the prime (not exclusive) mode of NMBD in opossums fed this UNBALANCED DIET. Beef liver, particularly RAW BEEF LIVER (which retains all its high Vitamin A content!) is the ABSOLUTELY WORST PROTEIN TO PROVIDE OPOSSUMS! … Besides, how many times have you seen an opossum bring down, kill and eat a cow?? Opossums certainly can and do kill and eat chickens and other birds. But COWS??!
PLEASE DO NOT USE OR RECOMMEND SUCH DIETS!!!
This report’s companion article in ‘Possum Tales, Vol. 10, No. 2-3, July, 1996 discusses the content and amounts National Opossum Society recommends in its Infant Formula and Adult Diet and gives seven sample days’ basic diet). It also touches upon comparisons between Esbilac, MultiMilk, and Milk Matrix 33/40 used in infant formulas. As a result of preparing for both these articles, we also have some specific comments on recommendations and “pit-falls” to avoid. Suggested Reading: Ettinger & Feldman, Editors. Joint and Skeletal Disorders, Section XVI, Textbook of Veterinary Internal Medicine; Diseases of the Dog and Cat. 4th Ed. (1995). WB Saunders; p. 2146.Hamilton, WJ. The Food of the Opossum in New York State, Journal of Wildlife Management, Vol. 15, #13 (July 1951), pp. 258-264.Hopkins, DD and Forbes, RB. Dietary Patters of the Virginia Opossum in an Urban Environment, The Murrelet, Vol. 61 (Spring 1980), pp. 20-30. Portland, OR.Kirschmann, JD and Dunne, LJ. Nutrition Almanac, 2nd Ed. (1984), pp. 313. [Note: There is a 4th Ed, which contains many new categories, but the 2nd Ed. Is actually more complete for foods used for wildlife.]Pennington, JA. Bowes & Church’s Food Values of Portions Commonly Used, 16th Ed. (1994). JB Lippincott, p. 483.Watt, BK and Merrill, AL. Agriculture Handbook No. 8, Composition of Foods, Raw, Processed, Prepared. (Dec. 1963) USDA, Wash, DC, p. 190; and the Revised version (1967-1991). =============================================================Opossums: The Unsung Heroes Against Lyme Disease And Other Tick-Borne Diseases
Several states in the U.S. are reporting record populations of ticks and increasing tick-borne disease transmission, like Lyme disease, but clearing your yard of these blood suckers might be only one opossum away. Yes, that giant rat-looking animal that plays dead when threatened and hisses like the devil’s spawn when scared is actually extremely beneficial to humans and other mammals. Opossums’ diets include snakes, snails, slugs, mice, rats, and carrion. Perhaps the most intriguing item on an opossum’s daily menu is an even more dreaded human foe: the tick. Opossums’ voracious appetite for ticks can nearly obliterate a tick population.
Scientist Rick Ostfeld points out that few ticks survive a run in with an opossum. These animals, often called filthy, are actually remarkable groomers and spend almost all of their free time grooming themselves. Ticks are attracted to these mammals, but most of them never survive on an opossum’s body long enough to taste a single drop of blood.
“So these opossums are walking around the forest floor, hoovering up ticks right and left,” Ostfeld explained, “killing over 90% of these things, and so they are really protecting our health.”
Michigan State University entomologist Howard Russell told the Detroit Free Press that the tick population is increasing. Russell says that both male and female ticks feed on blood and these thirsty bloodsuckers can transmit diseases like Lyme and Rocky Mountain spotted fever.
Robert Pinger, professor emeritus of physiology and health science at Ball State University, told the Indy Star that in the past couple of decades, the population of deer ticks, which is a host for Lyme disease, has grown exponentially in the U.S. According to Slate, reports of tick-borne diseases have doubled since 2003 and tripled since 1995 in America.
Possum Posse bragged about the opossum’s powers of fighting our tick foes after reading a study in the Proceedings of the Royal Society B.
“The new paper’s authors, Keesey et al., caught a range of tick hosts — white-footed mice, eastern chipmunks, gray squirrels, opossums, veeries, and catbirds — and experimentally infested them with ticks. They found a huge range of tick success across the six host species: almost half of all ticks introduced onto mice were able to feed, while only 3.5% of ticks introduced onto opossums were…Wild-caught opossums carried an average of almost 200 ticks — if that’s 3.5% of the ticks that try to feed on a opossum, then that means each opossum had attracted, and eaten, up to 5,500 ticks!”
That’s in just one week. An opossum successfully grooms off and kills and average of 5,686 larval ticks every week. The DFW Wildlife Coalition also sang praises to the opossum.
“When left alone, the opossum does not attack pets or other wildlife; he does not chew your telephone or electric wires, spread disease, dig up your flower bulbs or turn over your trash cans. On the contrary, the opossum does a great service in insect, venomous snake, and rodent control. He takes as his pay only what he eats, and maybe a dry place to sleep. The ‘possum tolerates our pets, our cars, prodding sticks, rocks and brooms. ‘Attacks’ by opossums are simply non-existent. When he gets too close, or accidentally moves into your attic space, he can be easily convinced to move along. If you are lucky enough to have one of these guys come around, you can rest assured he is cleaning up what he can, and will soon move along to help someone else.”
Many people use the rabies excuse for ridding their properties of opossums, but that justification is a false one. According to Wildlife Rescue and Rehabilitation, opossums are “rarely found to be rabid and appear to be resistant to many viral diseases such as distemper, parvovirus, and feline hepatitis” and this resistance to diseases is also seen with Lyme. The Poughkeepsie Journal reports that opossums don’t seem to be very good transmitters of Lyme disease even if they didn’t eat almost all of the ticks they encounter.
Ticks do transmit Lyme disease, and Lyme affects around 300,000 Americans a year. An opossum, normally viewed as nothing more than a filthy nuisance – stealing garbage, garden surplus and chicken eggs – kills over 5000 ticks on any given week. This super exterminator also kills venomous snakes and small rodents and cleans up carrion from our yards and fields. Perhaps allowing opossums to also steal some chicken eggs and garden veggies is a fair trade for decreasing tick-borne diseases like Lyme and all of the other benefits they offer.