Meet Our Mammal Nursery Patients
So the Mammal Nursery may be overrun with squirrels and bunnies, and raccoons are arriving daily, but what about those other mammals, which may not be as common, but still need just as much care and attention? In fact, some of it very precise care due to their unique needs.
Already this year we’ve cared for numerous Red Fox kits, half a dozen baby opossums (or ‘joeys’), woodchuck cubs, a couple baby mink, a young beaver kit, a handful of baby mice, a coyote pup, as well as several flying squirrels and chipmunks!
Here’s one of the very tiny mink on day of admission. Animals this small go home with volunteers who have special permits from the MN DNR.
The opossums may be the most interesting to me, simply because, unlike all other ‘placental’ mammals in North America, they are the only marsupial. The babies are born at a very early stage in their development, and then make their way to the mother’s pouch to continue growing. Once within the confines of the pouch (or ‘marsupium’), they latch onto one of the mother’s nipples, and do not let go until they are ready to leave. Juvenile opossums may ride on the back of their mother until they are old enough to leave her altogether.
Because infant opossums are attached to the mother’s nipple at all times, they will not learn, like placental mammals, how to ‘suckle’ from a syringe or bottle. This means that when caring for them at the WRC, we have to feed them their formula using a gavage tube which is carefully inserted through their esophagus into their stomach.
Woodchuck parents usually give birth to a litter of five young, which wean relatively quickly at around five weeks old. Woodchucks are known at the WRC for being bundles of ‘pure muscle,” and, as adults, exceptionally aggressive. The young start to exhibit the same characteristics at weaning age, and generally tend to be hostile toward humans. Although this may seem like a negative trait, we, as wildlife rehabbers, seek this type of behaviour! It is a good sign that when released they will not walk up to the next human they encounter, wanting food, and instead will behave like any other wild woodchuck. The cub we have at current is so young it cannot yet see; most likely only a couple of weeks old (they open their eyes during their third week).
At birth, mice ‘pups’ are hairless, blind and have closed (flattened) ears. They can weigh as little as 0.5g (0.02 oz)! They mature relatively quickly, and at about 3 weeks old (10 g or 0.35 oz) will stop nursing. At one month old they will leave the mother, and at 3 to 4 months old will be ready to mate! This may seem very fast, but things have to happen quickly when your life expectancy is, on average, only two years. We feed the mice pups at WRC with special ‘mice feeding tips’ and give them less than 0.5 ml of formula at each feeding. As soon as their eyes open we offer them sunflower seeds, small pieces of fruit and bird seed, and a soaked ‘rodent chow’ with formula. From there they quickly learn to forage on their own.
The flying squirrels we admitted were very young and orphaned when a dead tree was cut down. We’ll be able to determine whether they’re Southern Flying Squirrels or Northern Flying Squirrels when they’re a bit older. Here’s how tiny they were at the time of admission:
May 27th, 2012 at 11:18 am
Where are the opossums from? I thought they were found further south. Was surprised to see them at the nursery but am so impressed by all the work WRC does, thank you!
PS am thrilled w/ the comeback of the Blue Heron this year as I am sure everyone at WRC is also, that’s how I found you last year after the devastation.
May 28th, 2012 at 6:55 pm
Opossums are originally from Virginia (more appropriately termed, Virginia opossum) but they adapt well to new environments and are quickly venturing further and further north. During a cold winter, we often get many adults in with frostbite because they haven’t yet evolved for freezing temperatures!