Appendix B: Control tips for common nuisance species in New York
Opossum (Didelphis virginiana)
North America's only marsupial (mammals whose young develop in a pouch). They're
more closely related to kangaroos and koalas than to the other animals in the
4–14 pounds. Body is 15–20 inches long. They often suffer frostbite
and lose part of their tails and ears.
Signs of their presence:
- Sounds: growl, hiss, screech when threatened.
- Evidence of their feeding: Eggs that have been chewed into many small pieces.
(Raccoons usually remove one end of the shell without crushing it. Foxes carry
eggs away. Weasels and mink crush the entire egg.) Opossums maul chickens
beginning at the rear, while raccoons bite their heads off.
Tracks: look like they were made by little human hands, fingers spread wide
- Scats: are semi-liquid and don't last long. Left everywhere, even in the
den. When scared, possums may secrete a smelly, greenish fluid out of their
Opportunist. Opossums eat mostly meat (mainly insects or carrion) but they
also eat many plants, especially fruits and grains. They may eat garbage, compost,
pet food, bird seed, bird eggs, and young birds (turkeys, chickens, geese, and
game birds). They also eat voles, shrews, worms, and toads.
Typical activity patterns:
Social style: Solitary.
Daily activity: Usually nocturnal.
Hibernator? No, but does den up for days at a time when the weather is bad.
Distribution in NY and the Northeast: rural, suburban, and urban areas; parks.
Habitat: Wide ranging—arid to moist, woodsy to open, but more common near
streams and swamps. Dens in a different place three out of four nights (except
in the cold of winter). They find shelter under buildings, in brush heaps, hollow
logs or trees, old crow or squirrel nests, and rock crevices. Opossums may share
quarters with woodchucks, skunks, and rabbits.
Territory and home range: not territorial.
They have constantly shifting home ranges and may be considered nomadic. Home
range is usually 10–50 acres.
Pair bonding style: Polygamous. Females raise the young alone.
Breeding dates: February–June. Most
females, though, have just 1–2 litters per year. The young are born about
13 days after breeding.
Litter size: 6–16, average 8.
Life in a pouch: The tiny (about 1/2"
long) young are born blind and helpless. They must crawl into the mother's pouch
and attach to a nipple. They'll remain in the pouch for 7–8 weeks, firmly
attached to that nipple. Then, for about two weeks, they'll begin to explore
the world, often riding on the mother's back. They'll return to her pouch to
nurse. They're weaned at about 3 months old and are generally fully independent
by the time they're seven inches long.
Amount of time young remain with parents beyond weaning
date: 3–4 weeks.
Common nuisance situations:
Time of year: Any time of year.
What are they doing?
- Raid gardens, chicken coops, bird feeders, pet food, and garbage.
- Sometimes den in garages or attics and make a mess.
- A parasite found in the feces of opossums can contaminate water and food
sources for horses (both hay and feed). This parasite can transmit a disease
to horses, called "equine protozoal myelitis." This disease affects
the nervous system and can cause lameness.
- Disease risks to people: mange, rabies (rarely).
De-bunking myths about opossums:
- A hissing or drooling opossum is not necessarily rabid. When threatened,
a healthy opossum may bare its teeth, make a lot of noise, drool, bite, or
leak a nasty fluid out of its rear. Stress may cause them to play dead, which
might confuse predators and keep them from being eaten.
Legal status in New York:
Protected. Game species with set season. From ECL 11-0523:
"7. Whenever black, grey and fox squirrels, opossums or weasels are injuring
property on occupied farms or lands or dwellings, they may be taken at any time
in any manner, by the owners or occupants thereof or by a person authorized
in writing by such owner or occupant.
9. Varying hares, cottontail rabbits, skunks, black, grey and fox squirrels,
raccoons, opossums or weasels taken pursuant to this section in the closed season
or in a manner not permitted by section 11-0901 shall be immediately buried
or cremated. No person shall possess or traffic in such skunks or raccoons or
the pelts thereof or in such varying hares or cottontail rabbits or the flesh
- Opossums move around a lot, and usually don't stay in one den site. If the
problem was caused by an individual opossum, it will probably leave on its
own. Just realize that the problem could be caused by different animals who
are all attracted by the same source of food, water, or shelter.
Remove food sources and shelter:
- Put trash out in morning instead of the evening.
- Opossum-proof garbage can with a tight fitting lid, or secure it with straps.
- Don't leave pet food out at night.
- Enclose compost piles in a framed box using hardware cloth; in a sturdy
container, such as a 55-gallon drum; or in a commercial composter.
- Keep the area under bird feeders clean.
- Remove brush piles and debris.
- Close garage doors at night.
Protect vulnerable livestock:
- Close doors to poultry houses, and if birds are caged, keep those doors
- To keep opossums from climbing over a wire mesh fence, install a tightly
stretched electric wire near the top of the fence, about 3" out from
- Install an electric fence around the hen house, or use hardware cloth to
cover holes and potential entrances.
- Opossums are easily caught with cage traps.
- Foothold traps (# 1 or #1 1/2) are also effective.
- Set traps along fence rows or trailways in a dirt hole, cubby, or running
- They prefer slightly spoiled baits, such as cheese or fruit. If you use
a box trap with these baits, you may also capture skunks so be prepared to
- They're slow, so it's possible to capture them by hand, or with the use
of a catchpole. Grasp the end of the tail (wear heavy gloves because they
have sharp teeth). If you're holding an opossum and it tries to climb its
tail to reach (and bite) your hand, lower it to the ground, where it will
attempt to crawl away.
- Assume that a female opossum has young in her pouch during the rearing season
(March–August). The females are not likely to retrieve young, so make
sure that all her babies are either in her pouch or clinging to her before
you release her.
- Body-gripping trap, #120 or #160, set in a vertical cubby for greater selectivity
(see chapter five for details).
Preferred killing methods:
- CO2 chamber
- Lethal trap
- Lethal injection of barbiturate, if possible
- Shooting, using a shotgun with #6 shot or larger, or a .22 caliber rifle
(heart/lungs shot is preferred). Why is just the heart/lungs shot listed as
preferred? The head shot is difficult because opossums have very small brains
located in a relatively large skull—and there's a strong crest on their
skull, which can deflect the bullet. See the illustrations on the next page
for more information about the head shot.
Properly targeting a head shot for an opossum is challenging because their
brains are much smaller than you'd guess, looking at the size of their heads.
Looking at the side of the opossum's head, imagine a direct line between the
eye and ear. Now, aim slightly below that, closer to the base of the ear.
Position the gun very close to the head.
Acceptable killing methods:
- Gunshot to the head (this is a difficult target and should only be attempted
by NWCOs who are more experienced and skilled in the use of firearms)
- Stunning and chest compression
- Stunning and exsanguination