🔎 Species ID & Natural History · 8 min
Mammals: feeding groups and life histories
Why this matters
Weaning ages and natural history decide whether an animal in front of you is an orphan at all, and when it can go back out.
By the end of this lesson you will be able to
- Classify mammals by feeding group and dentition
- Recall key weaning ages and developmental milestones
- Recognize normal parental behavior that looks like abandonment
Feeding groups
| Group | Teeth | New York examples |
|---|---|---|
| Carnivore | Sharp canines for tearing | Long-tailed weasel, mink, bobcat, fisher, all snakes, hawks and owls |
| Omnivore | Sharp canines and grinding molars | Raccoon, opossum, skunk, black bear |
| Herbivore | Flat grinding molars, no sharp canines | Woodchuck, beaver, deer, cottontail, most rodents |
Note that being an omnivore means an animal eats many things depending on seasonal availability. It does not mean it has a highly specialized diet.
Milestones the exam likes
| Species | Fact |
|---|---|
| Cottontail rabbit | Born blind and furless. Weaned and independent at about 4 weeks, even though still small. Mother leaves the covered nest all day and returns only at dawn and dusk. |
| Snowshoe hare | Born eyes open, fully furred, hopping in a day or two. Not a rodent: rabbits and hares are lagomorphs. |
| Gray squirrel | Born naked and blind. Eyes open about 5 weeks, fully weaned at 12 to 16 weeks (3 to 4 months). |
| Flying squirrel | Begins to glide at about 2 months. It glides on a skin flap between wrist and ankle, it does not truly fly. |
| Virginia opossum | North America's only marsupial. Newborns are the size of honeybees. Leave the pouch around 2 to 2.5 months, independent at 12 to 13 weeks. Lives only 1 to 3 years in the wild. Juveniles can be aggressive toward littermates, even cannibalistic. |
| White-tailed deer | Fawns fully weaned at 4 months, before the spots fade, but stay with the doe until the following spring. A newborn fawn has very little scent. |
| Woodchuck | A true hibernator, active again in late February and March. |
| Black bear | The only bear native to eastern North America. Not a true hibernator: fully alert if disturbed. Color varies. |
| Bobcat | The most common wildcat in New York, solitary hunter. Kittens born late April or May, eyes open at 10 days. Lynx are rare, grayer, larger-footed. |
| Porcupine | Poor vision, good sense of smell. Quills are barbed, not poisonous, and cannot be thrown. |
| Mustelids | Weasels, mink, otters, fishers, pine martens. Ermine is another name for the short-tailed weasel, which turns white in winter. Fishers hunt porcupines. |
| Beaver | Herbivore, does not eat fish. Kits stay with the family 2 to 3 years. Fiercely territorial, so never move one to a strange colony. Hind gut fermenter with a delicate digestive system. |
Absent parents are usually normal parents
It is natural for some mammals to leave their young unattended for long periods, returning only to feed. Cottontails and white-tailed deer both do this. The fawn lying alone in tall grass and the nest of rabbits in the lawn are not abandoned, they are being parented correctly.
This lesson is part of the NY Wildlife Rehabilitator Exam course. Open it in the course to answer the retrieval checks that go with it, track what you have read, and quiz the whole unit. Lessons, quizzes and the glossary are free.