Opossum

North America’s only marsupial

The Virginia opossum is the only marsupial native to North America — every other native North American mammal is a placental mammal. The opossum represents an evolutionary anomaly: marsupials are otherwise primarily found in Australia and South America.

The species has been expanding its range northward for centuries — historically tropical and subtropical, opossums have moved into Canadian provinces in the past 100+ years, helped by suburban food sources and climate change.

50 teeth — most of any North American mammal

Opossums have the most teeth of any North American land mammal — a full set of 50 teeth, more than dogs (42), cats (30), or humans (32). The teeth reflect the species’ generalist diet:

• Sharp incisors for fruit
• Canines for animal prey
• Molars for plant material
• Total dental coverage for opportunistic eating

This dental versatility helps explain the opossum’s success — they can eat almost anything.

”Playing dead”

The famous “playing dead” behavior — properly called thanatosis — happens when an opossum is severely frightened. The animal:

1. Falls onto its side in a stiff posture
2. Tongue lolls out
3. Eyes glaze over
4. Body releases foul-smelling glandular secretions
5. Heart rate drops, breathing slows
6. Appears completely dead for minutes to hours

The behavior is involuntary — it’s a stress response, not conscious deception. Many predators that would normally eat live prey are confused or repelled by the apparent death and decay smell.

The opossum eventually “recovers” once danger has passed — sometimes hours later — and resumes normal behavior.

Pouch-rearing

Like other marsupials, opossums give birth to extremely underdeveloped young that complete development in the mother’s pouch:

• Newborn opossums are about the size of a honeybee (0.13 g)
• Crawl from birth canal to pouch with tiny forelimbs
• Attach to a teat for 2-3 months of continued development
• Emerge from pouch at about 60-100 days old, then ride on mother’s back

A typical opossum litter has 8-13 young, but only those who reach a teat survive. The mother has 13 teats; young that don’t claim a teat in time perish.

Tick consumption

Recent research has identified opossums as major consumers of ticks:

• A single opossum can consume 5,000+ ticks per season
• Their grooming behavior efficiently removes attached ticks
• Significantly reduces local tick populations
• Helps control Lyme disease and other tick-borne pathogens

This has shifted public perception — formerly considered pests, opossums are increasingly recognized as beneficial in suburban ecosystems for their tick-eating contribution.

Resistance to snake venom

Opossums have remarkable resistance to snake venom — including pit viper species like rattlesnakes and copperheads. The species has evolved blood proteins that neutralize venoms, providing protection during prey opportunities and accidental encounters.

This resistance has been studied for medical applications — opossum venom-resistance proteins have potential for treating snakebite victims. Several research programs investigate isolating and synthesizing these proteins for human therapeutic use.

”Possum” vs “opossum”

Confusing terminology: the Virginia opossum is the proper name of the North American species. “Possum” technically refers to Australian possums — entirely different animal species in the family Phalangeridae.

In common American speech, the Virginia opossum is often called simply “possum” — but biologists distinguish the two for accuracy. The shared name reflects early European naming confusion when the Australian species was discovered.

Short lives, fast reproduction

Opossums have unusually short lifespans for mammals their size — typically 1-3 years in the wild. The brief life is likely an evolutionary adaptation to high predation rates: opossums reproduce early, often, and prolifically rather than investing in long-term survival.

Females typically have 2 litters per year, producing 8-13 young per litter. This reproductive strategy maintains population despite individual short lives — and helps explain the species’ continued range expansion.