Cannibalism has been found to be a normal behavior in many animal species in the wild. It may be part of natural selection, a way to eliminate a young or old animal that is sick or unhealthy. A mother may cannibalize one or more of her unhealthy young to eliminate a weak animal and devote more time and resources (food) to the more viable and survivable young.
In the opossum, however, it does not seem to be a “normal” behavior in the unconfined opossum in the wild. Although incidences of cannibalism are rare, it has been known to occur in captivity. When it does occur, the reason can usually be traced back to poor husbandry. In addition to the obvious definition of eating conspecifics (other opossums), it also includes self-mutilation.
- Poor husbandry
- Improper diet
- Insufficient quantity of food/water
- Mixing different sized animals
- Mixing litters
- Placing sick/injured opossum in cage with healthy litter
Prevention: It is important to provide adequate cage space, limit the number of opossums in each cage, provide multiple levels for climbing and separation and at least 2-3 den boxes per cage. Contact OSUS for cage recommendations or you can contact the National Wildlife Rehabilitators Association (NWRA) which produces a Minimum Standards for housing all species, updated every few years. Many states require their licensed rehabilitators to adhere to the NWRA’s Minimum Standards or at least as closely as possible. Never overcrowd! It is better to turn opossums away than to subject the animals to an overcrowding situation setting them and YOU up for the possibility of cannibalism!
Also, minimize stress. Do not talk to the confined opossums and/or pet them. This is stressful, not calming! In addition to den boxes, provide pouches or towels they can burrow under inside. When they are moved outside prior to release, provide climbing limbs with heavily leaved branches for them to hide within, in addition to the den boxes. Keep the cage or a portion of it covered so the opossum cannot see you, cover with towels inside, staple shade cloth on portions of outdoor cages. Keep children, pets and domestic livestock away from the caged opossums. Keep noise levels and contact to a minimum. You should only go into the cage to check on the opossums, monitor their health, medicate if needed, feed them and clean their cage. Make sure you are able to view their sleeping area and can see their tails and feet. Use monotone light-colored material to line their den boxes, pouches or hammocks so you can readily see any body fluid stains on the material.
It is best to avoid mixing litters. If limited caging requires you to do so, preferably introduce the young before their eyes have opened. If introducing after their eyes have opened, do so with extreme caution and careful monitoring. Try inserting the strange opossum in its own separate, smaller pouch next to the pouch containing the other opossums all sleeping together during the day. That way they will have spent all their sleeping time breathing in each other’s scent and may not seem as strange to each other. (See picture below)
Watch for problems and any signs of aggression. Watch for missing or chewed upon ear tips, tail tips, bloody digits, punctures and any sign of blood in the cage/bedding. Watch for lunging or snapping at each other. Listen for “cacking” sounds while they are in their den area. The same “cacking noise” of displeasure they make when you rouse them from sleep to feed them when they are younger.
Any injuries observed, however slight, separate the injured into a different cage!
Watch for any vigorous licking upon one spot of a cage mate. Opossums will casually groom themselves and administer a few licks to a nearby littermate(s) upon first rising in the evening and after eating. Pre-cannibalistic behavior is a frenetic licking. The aggressor will lick so hard they cause a localized spot of hair loss, then the aggressor will start chewing on its victim. For some reason, the victim opossum doesn’t make much of an effort to escape this assault.
View this 13 second video clip of an opossum licking a mouse in preparation of consuming it. This is an example of the frenetic, concentrated licking prior to taking bites:
I’ve experienced cannibalism five times in the 35 years I’ve been rehabilitating opossums. I still don’t feel I’ve pinpointed what exactly precipitates this behavior. My experience is it is one opossum that is the aggressor. I tried to pick out which one by just watching them interact. I figured out the licking when I found a soaking wet opossum, then watched until the culprit approached again and started licking again.
The other time I found I had 4 out of 7 opossums with nipped tails and ear tips. I couldn’t decide which of the uninjured opossums was the culprit. So that night, I withheld food for a couple hours beyond the normal feeding time. When I set the food bowl in the cage, all the opossums came piling out of the den box. One female pushed her way to the bowl and threw her forepaw around a littermate’s neck, initiating a headlock to get him to back away from the bowl. I knew I had my culprit, grabbed her, and put her in a separate cage I already had set up. She was perturbed! The rest of the night she crawled up and down the bars of her cage, making “cacking noises.”
My five experiences with cannibalism were always after the opossum reached self-feeding age. My first three experiences were when I placed the opossums in an outdoor run, just prior to release and I attribute those incidents to not providing enough concealment for them. The first instance, I placed their food bowl in the run for the evening and stood back to observe them come out to eat. I realized two opossums didn’t come out of the den box to eat. I pulled the den box out to examine the opossums. There was only one opossum to pull out. I pulled her out and she was absolutely rotund, stuffed to the gills. Of the other opossum there was no sign, not a hair, piece of bone nor flesh. The bedding looked liked it had been licked clean of blood. The horrible realization of the situation hit me like a punch in the gut. The other two cases were younger litters that I had raised since formula feeding and were inside where I could easily notice anything amiss. I don’t know what, or if, I did anything wrong with their husbandry, but I recognized the possible signs of cannibalism and separated them quickly.
Thankfully, it is a rare occurrence. Knowing proper husbandry, the pre-cursors to cannibalism and NEVER PLACING A SICK OR INJURED ANIMAL IN A CAGE WITH OTHERS should prevent you from experiencing cannibalism. Even a slight wound may be an invitation for another to cannibalize.
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