Mammals on the move

As spring progresses, we’re seeing ever more mammals on the move. They’re mating and having young and in search of extra sustenance for these activities. The animals whom we unfortunately see dead alongside — or on — roads often include members of the rodent group: groundhogs, squirrels and chipmunks.

Would you be surprised to discover that about 40% of all mammal species are rodents? When people hear that term, many immediately think of rats and mice (i.e., “vermin”) but the group is more diverse. What they all have in common is a pair of incisor teeth in their upper and lower jaws which never stop growing.

groundhog P3203437© Maria de Bruyn (2) res    groundhog P2249052© Maria de Bruyn sgd res

The woodchucks (another name for groundhogs, Marmota monax) whom I’ve seen the past couple months have been seeking food at two local reserves. The name woodchuck does not indicate one of their activities, however. It comes from the Native American name “wuchak,” which means “digger”.

groundhog P3203312© Maria de Bruyn (2) res

These rodents are fairly solitary but live near family members. They greet one another, with one individual touching the other’s mouth with his or her nose. Their ever-growing teeth are bright white, unlike the dingier teeth of other rodents.

groundhog P3203339 © Maria de Bruyn (2) res  groundhog P2249047© Maria de Bruyn (2 res)

They have both summer and winter dens in well-drained areas. The summer abode is near food sources and the winter one is situated near areas with protective cover. Their ear canals are kept clean while they burrow because their round ears can cover the auditory opening, so no dirt or debris gets in. They usually have more than one entrance to dens with multiple tunnels and spaces, including an escape hole!

groundhog P3203375© Maria de Bruyn (2 res)

groundhog P2248981© Maria de Bruyn res

If there is danger, they call out a warning by giving a high-pitched whistle, which has led to them also being called “whistle pigs.” They also use other vocalizations and scent glands to communicate with one another. To escape predators, these hefty mammals can climb trees.

groundhog P3203306© Maria de Bruyn (2) res  groundhog P3203338 (2) (2) res

groundhog P2249010 © Maria de Bruyn res

We may not see the groundhogs too often — unless you have a garden. They enjoy eating alfalfa, dandelions and clover, but I can attest to their penchant for savoring tasty vegetables like tomatoes. One came up onto my porch to sample the wares in my container garden! In my experience, however, they tend not to stay around too long.

Eastern gray squirrel P2090522© Maria de Bruyn (2 res)

Eastern gray squirrel P2218598© Maria de Bruyn (2 res)A rodent that we may see much more often in yards, parks, public gardens and along trails are the Eastern gray squirrels (Sciurus carolinensis). Some people find them amusing to watch, while others wish they would just go away — especially birders who end up spending more on bird food than they planned because these clever rodents find innumerable ways to get up onto bird feeders. Facebook groups for birders regularly have postings by people asking for suggestions on how to thwart squirrels from gaining access to their feeders.

Eastern gray squirrel IMG_0418© Maria de Bruyn (2) resI, too, continue with ongoing efforts to outwit these feeder marauders. They are not shy, coming up on the front porch to look in on my indoor cats.

They jump from trees onto the roof and then perch at the edge, calculating whether they could accomplish a far enough jump to reach some feeders.

Eastern gray squirrel P6170627© Maria de Bruyn (2) res      Eastern gray squirrel P6170625© Maria de Bruyn (2 ) res

I’ve moved my feeder poles away from trees, roofs, tall bushes and shrubs numerous times since squirrels can successfully launch themselves to a feeder 10 feet away.

Eastern gray squirrel P5255669© Maria de Bruyn (2 res) In my yard, they have gnawed at the bottom of a baffle designed to keep them off poles as they try to pull it down. Their ability to chew through plastic and metal may be one reason that they manage to keep their dentition to “normal” lengths since their teeth grow about 6 inches per year.

Eastern gray squirrel P5255651© Maria de Bruyn (2) res

Eastern gray squirrel P5255633© Maria de Bruyn (2) res

In the past week, one especially athletic individual has figured out how to jump over the baffle from the ground to get to feeders.

Eastern gray squirrel P2197722© Maria de Bruyn (2) res

Eastern gray squirrel P2197741© Maria de Bruyn (2 res)

I raised the baffle and put chicken wire on it in an experiment to see if this would deter this determined rodent. It didn’t. I finally put a second sloping baffle above the tube baffle and the squirrel slid off in its latest attempt to get to the fruit and nuts.

Eastern gray squirrel PA241931© Maria de Bruyn res (2)Many nature observers do admire squirrels’ cleverness. For example, squirrels spend a lot of time hiding food in caches dug in the ground. To outwit other squirrels and rodents who might be watching, they will prepare a hole, pretend to deposit food, and cover it up. Then they will go somewhere else where they don’t see a rival watching and hide the food in another place.

An anatomical peculiarity these animals share with other rodents is that they are unable to burp, have heartburn or vomit. (How this was discovered is probably something I don’t want to know.) They also can suffer from insects, carrying ticks and having botflies lay eggs under the skin as happened to this individual whom I spotted in a city park.

Eastern gray squirrel PA170160© Maria de Bruyn ed (2) res

Scientists have determined that gray squirrels’ spatial memory is excellent as they later are able to retrieve about 80% of food stored in their numerous (up to several thousand!) caches. One university study showed that almost two years after some squirrels learned to solve a tricky problem to gain access to a desire food, they were still able to recall the solution to the problem.

Eastern gray squirrel P6267310© Maria de Bruyn res (2)

The squirrels are quite vocal and have a variety of calls, including chattering, squeaking, raspy noises and one particular call that I have come to recognize as a warning that a hawk is near the yard. And they not only avoid predators but have been shown to be able to remember whether people are their friends or enemies!

In our area, the number of gray squirrels is quite high, even when they are often hunted and caught by local predators. It would surprise some of my friends and neighbors, I’m sure, if they learned that, in July 1856, a crowd went to New York City’s (NYC) Central Park to see what was then considered a rare gray squirrel! Other cities also had low numbers; in 1847, Philadelphia initiated one of the first squirrel reintroduction projects, followed by NYC, Boston and other municipalities.

Eastern chipmunk PC292310© Maria de Bruyn (2) resA rodent that many people tend to like more than groundhogs and squirrels is the diminutive Eastern chipmunk (Tamias striatus). The “cuteness” factor undoubtedly plays a role as these active little animals do tend to look a bit endearing.

   

They also look amusing to many people when they are filling their cheek pouches to carry food home. These pouches can stretch to three times the size of their heads so that they can build up a sizeable store of saved food for winter.

Eastern chipmunk IMG_0243© Maria de Bruyn (2 res)

Because they have two litters a year, encounter so much competition for seed and nuts, and because they must work hard to gather supplies, I have on occasion given them a little dish of food for them to gather with ease. Since I just love watching them, I get something out of it, too.

Eastern chipmunk IMG_0273 © Maria de Bruyn (2 res)

Eastern chipmunk P6094693© Maria de Bruyn (2 res)

These rodents live in burrows dug about 3 feet underground. The multiple “rooms” (one used for nesting and others for food storage) can be connected by alleyways up to 30 feet or so in length. They can also climb; one individual in my yard has been imitating the squirrels who run up my bird feeder poles.

Eastern chipmunk PB283524© Maria de Bruyn res   Eastern chipmunk PB283523© Maria de Bruyn res (2)

Eastern chipmunk P2010412© Maria de Bruyn (2 res

My observations have convinced me that these little creatures are very brave. When I’ve spread some bird seed on the ground, they will join the towhees, robins, sparrows and other birds to feed. When squirrels move in and try to chase them off, they will retreat but only for a minute or so and then they return to continue gathering seed.

Eastern chipmunk P3022838© Maria de Bruyn ed (2) res

One day, some white-tailed deer moved in to also eat some of the seed on the ground. A chipmunk was there, and one deer very tenderly nuzzled it a bit in a non-aggressive way. The brave little rodent, confronted with a touch from a being hundreds of times its size, just kept filling its pouch! It was a touching moment (poorly photographed through the screened porch but nevertheless showing the event).

Eastern chipmunk P1304359 © Maria de Bruyn ed res

Because chipmunks don’t tend to eat vegetable garden plants or figure out ways to deplete bird food sources, they may be the rodent that people like best among the garden and field visitors.

Eastern chipmunk P1304354© Maria de Bruyn res (2)

Eastern chipmunk P3022806 © Maria de Bruyn (2 res)

If you take the time to just observe these three commonly seen mammals, however, you might find that they all have behaviors you find interesting and/or amusing. So please try not to hit them on the road. Tolerating their presence, especially given how much of their wild habitat has been destroyed, means that we are at least helping promote biodiversity in our environment.

Eastern chipmunk P3044769 © Maria de Bruyn (2) res