To catch a deer mouse (Peromyscus maniculatus)

Notice the bicolored tail, dark above, white below, on the
deer mouse (Peromyscus maniculatus)
Photo by Brad Sylvester. Copyright 2012.

There are a number of different species and subspecies that are popularly called deer mouse, wood mouse, or white-footed mouse. Many have a similar appearance and if you just catch a glimpse of one or are just looking at a top view as it sits in a bucket waiting to be carried far away from the house, then it can be hard to tell the difference between them. This appears to be a deer mouse of the species Peromyscus maniculatus.

One of the best websites detailing the differences between the deer mouse and similar species is enature.com. The tail is one key point of identification. In Peromyscus maniculatus, the tail is dark above and light below. There’s a clear demarcation of the two colors on the tail which should be about the same length as the rest of the mouse. The bicolored tail is shown clearly in the photo at the top left of this post.

The white underbelly with the tail details, the color of the top of the mouse’s body, the large, bulging eyes, and the location where it was found (New Hampshire) make it a pretty sure bet that this is, in fact, Peromyscus maniculatus, even though there are four species of mice that are native to New Hampshire and one (the house mouse – Mus musculus) that was introduced from Europe and is now firmly established here and throughout North America . If you look up images of the species by the common name on the Internet, however, odds are about fifty-fifty that you’ll get something other than Peromyscus maniculatus.

Deer mice typically live in the forest and fields and do quite well without coming into human houses during the winter. They will burrow under the snow seeking seeds and other edible plant material. In my yard, they will eat the soft green bark of bushes and shrubs below the snow so the damage isn’t visible until the snow melts in the spring. Once the snow does melt, however, the gnaw marks are very clear often girdling the bush (removing the bark all the way around it), which kills the plant.

From the top, not enough distinguishing features can be seen
for a positive identification of the deer mouse (Peromyscus
maniculatus).
Photo by Brad Sylvester. Copyright 2012.

We do, however, get an occasional mouse inside the house when there is a period of particularly cold or severe winter weather. They come in seeking better shelter and a more ready source of food.
Mice are prolific breeders. Just a couple slipping into the house can turn into an infestation if not quickly eliminated. Once inside, they’ll also look for whatever foods they can find there: dog food, cat food, my food.

For that reason, and because the area in which we live has carpenter ants which would like nothing better than to chew up the structural wood of our house until it falls down around our ears, our house is serviced regularly by an exterminator. They bait for rodents in the crawl spaces and little nooks and crannies where they might be otherwise found. This is quite effective and we generally don’t have mice around, at least not for very long.

Outside, however, there are the tunnels in the snow that reveal their presence and favored routes. To catch one, I just needed to put this live capture mouse trap , baited with peanut butter, in the walkway near the opening to one of the snow tunnels.   That's what led to the photo opp. for this little guy. This deer mouse was released unharmed.

Quick Facts about the Deer Mouse (Peromyscus maniculatus):

Diet: The deer mouse eats seeds, insects, berries, nuts and mushrooms. The US Forestry Service doesn't list the green inner bark of shrubs as part of the deer mouse diet, but I have the dead ornamentals to prove it, although they don't seem to choose it when other food is available in the summer. Since they seem to only eat it when it is under the snow, it is hard to catch them in the act. In this case, however, the tunnels, footprints, and captured deer mouse itself provide pretty solid evidence that this is the species that is eating the bark. 

Range: According to US Forestry Service, the deer mouse lives pretty much all throughout the continental United States except the extreme southeast (northern Georgia yes, Florida no). It can also be found in parts of Mexico and Canada west to southeastern Alaska.

Habitat: Deer mice live in just about every type of habitat: forests, fields, scrub, canyons, desert, you name it. They build nests just about everywhere, too. Deer mouse nests can be found high in trees, in underground burrows, in scrub piles, rock piles, and all sorts of man-made structures (like houses, cars, and barbecue grills) where they can stuff leaves, grass and other soft insulation to make it more comfortable.

Reproduction: Litter sizes may range from one to nine, but three to five is more typical. Gestation lasts 22-26 days and females may have several litters each year. The US Forestry site says that as many as 14 litters in a single year have been reported. At about 48 days of age, female deer mice are sexually mature and ready to begin having litters of their own.

When is it here? The deer mouse is a year-round resident of New Hampshire.

Where does it go int he winter? The deer mouse does not hibernate and is fully active throughout the winter.

Territory:

Predators: What eats deer mice? Many New England animals eat deer mice. The owl, coyote, fox, bobcat, house cat, snakes, weasels, martens, fisher cats, mink, chickens, and even skunks will all eat deer mice either regularly or opportunistically. With so many predators, the deer mouse relies on frequent litters and rapid maturation to maintain its population.

Deer Mouse Taxonomy:

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Cricetidae
Genus: Peromyscus
Species: Peromyscus maniculatus


Sourcing Note: Because the range of the deer mouse covers such a wide variety of climates and geography, there are variations in reports of diet, litter size, litter frequency and other aspects of behavior among different sources. They may all be correct for different regions, but I have used data from the US Forestry service website linked above for information that I have not directly observed myself.

Double-lined Prominent Caterpillar Moth (Lochmaeus bilineata) - Or is it?

I’ve talked about identifying whether a particular insect is a butterfly or a moth, but what if it’s still a caterpillar? Often caterpillars have distinctive colors and patterns as well and can be identified that way. Some, however, like the Variable Oakleaf Caterpillar and the Double-lined Prominent Caterpillar, fall into the variable category, meaning that different individuals of the species may have substantially different coloration.

It’s not a minor variation either. It can be the difference between a caterpillar that is all green with narrow yellow stripes and a caterpillar that is green with a broad irregular reddish brown patch down the length of its back.  If I saw the two extremes of the Variable Oakleaf Caterpillar side by side, I would never have guessed that they were the same species.

That can be tricky if you are trying to identify a caterpillar by searching through photos. If you happen upon a photo of a color variant much different from your specimen, you may rule it out too early. That happened with me on the caterpillar pictured below.

Double-lined Prominent Caterpillar (Moth) - Lochmaeus bilineata (probably)
Photo by Brad Sylvester, copyright 2011, all rights reserved

At first, I thought that it could not be a Lochmaeus manteo (Variable Oakleaf Caterpillar), based on a few images I saw with a pronounced reddish saddle. Neither, however, could I find much else that was similar except the closely related Lochmaeus bilineata (Double-lined Prominent). By the way, Bugguide.net says the two may be indistinguishable in larval form, so technically, my specimen could be either species.  With some further searching and the use of a handy identification tool at Discover Life, I came back again to Lochmaeus bilineata and discovered some images of variants without the red marking on the back. These were nearly identical to my specimen, with the exception of two pairs of little red wart-like structures which should be present, but are not visible in my photos. Despite this, I am as certain as I can be that it is one of the two Lochmaeus species, and most probably Lochmaeus bilineatus or the Double-lined Prominent.

Clues to caterpillar identification

besides the color, pattern, presence of bristles, horns on its head or tail, and other distinguishing physical features, another clue to use to identify caterpillars is the type of food, usually leaves of some sort, which they eat. Some species of caterpillar are very picky about what they eat. In this case, both of the Lochmaeus caterpillars eat oak and other tree leaves. The Double-lined Prominent caterpillar that I found was eating a beech tree leaf, when I encountered it, although there is certainly plenty of oak on the property as well.

Another way to identify a caterpillar’s species is to see what it turns into after it undergoes metamorphosis. This, obviously, takes a little more time, and involves some risk to the caterpillar if you can’t keep it in a proper environment. If you aren’t sure what it eats, you shouldn’t even try to keep it captive until it pupates and forms a chrysalis or a cocoon. Even the chrysalis itself most likely requires the humidity and temperature to stay within a certain range to keep it viable. Ambient outdoor conditions for your region can be a good clue though.

If I had tried to keep the Double-lined Prominent caterpillar until it became a butterfly or moth, in this case, a moth. It would have formed a silken-thread cocoon and emerged as a pretty non-descript gray-patterned moth of small to medium size.

Quick facts about the Double-lined Prominent Caterpillar Moth (Lochmaeus bilineata)

Diet: Tree leaves: beech, oak, birch, elm, basswood, linden

Range: From New Mexico in the Southwest and Saskatchewan in the northwest eastward to the Atlantic Coast.

IUCN Redlist Status: Prevalent, not-listed

When they are here: Adult Double-lined Prominent moths can be found from June through August. I didn’t have a resource with good information on the larval life-cycle, but my BEST GUESS is that they overwinter in caterpillar form and form a cocoon when it gets warm in the spring, perhaps late April or early June based on the presence of the adult moth. The larva is certainly present in early-mid July, when I found this specimen.

Habitat: Deciduous woods