The rodent relocation program

We have started a rodent relocation program of sorts in our house. We live in southeastern Pennsylvania and our 200-year-old house is a fond nesting spot for many small creatures. I truly can't stand killing anything (okay, not true, ticks are fair game) so we catch them in traps and release them somewhere far away from our house. Our traps are small grey and plastic- they tip when the mouse goes in shutting the door behind them so I have never had a chance to see what we were catching. When we release them, they don't stick around to be observed. Our gerbil died a while back so my daughter and I got the idea of releasing a prisoner into the gerbil cage to see what we caught. Turned out to be a deer mouse. Mikaela immediately named him (her?) Harry. So for a few days we thought we would watch and check out his antics. As unhomeschoolers we can find nature and science everywhere we turn. We were surprised at how brave he is. He comes right up to the edge of the cage and watches us. He will then perform an array of stunts that include running wildly around the cage and hanging upside down from the bars and then comes back to look at us as if to say, so are you impressed? (Of course he could also be saying Let me out of this freaking cage!) My daughter likes to stuff part of a tissue through the bars at night before she goes to bed to see that he has pulled the whole thing in and shredded it to expand on his nest by morning. So, science aside, we have now grown found of this little guy who seems to perform for us. Although we have signs of spring everywhere we turn (the snowbells are out!) we are wondering if we relocate Harry to a park near us if he will be able to survive and find other deer mice buddies when it is still dipping into the thirties at night. I started to research deer mice on the web and found Rob Sandelin’s nature web site. I’m in love with this guy! His writing is wonderful. I want to follow him around for a while so I can experience all the nature he sees that I surely pass by. When I read his 2005 nature notes about putting a vole in his pant pocket I knew I had found the guy to ask. A guy who puts a vole in his pant pocket might understand our dilemma and have some more info. When I read his 2008 notes about how he held a baby deer mouse in his hands to warm it up, I knew I had the right guy. Below I have copied his field notes that pertain to deer mice. We still had a few more questions so I emailed him. We are also curious about how far an average deer mouse can travel and find his way home. You know where I am going with this one! We love Harry but when we set him free we really don’t want to see him again!



From Northwest Natural History by Rob Sanelin

End of September 2005 field notes
As the nights cool off some of the rodents from outside are keen to find a warmer spot and look for ways to squeeze into your house. House mice are quite numerous and can squeeze into cracks only 1/3 of an inch thick, the only limiting factor they have is how wide their little skull is. House mice and deer mice are prolific breeders, both can have 5 or more litters a year, thus one female might produce 35 or more of her kind. Since both species become sexually mature at about a month old, the mouse math quickly goes exponential. Thankfully, mice are sort of the lunchbox of the predator world and mice can only breed in relation to food supply, which varies.



April 2006 field notes
The first annual broods of deer mice are curled up together, their hairless pink bodies huddled in a mousey ball for warmth. These babies will be out of their grass and moss lined nest in about three weeks, providing food for the variety of predators that depend on their prodigious reproductive rates. At six weeks of age a female can become pregnant, and if she should live so long, she could be a great-great grandmother by fall. Populations of tiny rodents can have a large impact on what kinds of plants might grow in an area. Seedling plants offer high nutritional values and are often primary food resources for rodents. If the rodent population is high, and rodents prefer maple seedlings, then maples may not succeed in getting any of its seedlings large enough to where such predation is less effective. In an enclosure study done on the Olympic Peninsula, Deer mice ate every single Cottonwood and Big-leaf maple seedling in the enclosure. The ebb and flow of populations flux from year to year and decade to decade. So perhaps if owls and weasels decline, the mouse population increases, and maple trees might decline. Or, perhaps the very existence of maple trees is an artifact caused by a temporary population bloom of weasels many years ago which repressed the rodents long enough that the trees could grow beyond their reach. The landscape we see today was shaped by forces of several years ago and we can only guess at why things are the way they are.




April 2008 field notes
The deer mice are having babies and I rescued a mouseling that was wet and cold by putting it in my pocket. The warmth of my hands around it brought it back to alert activity so I set the squirmy tyke down at the edge of the wood, said my goodbye and good luck and then walked a few paces to a sunny spot to sit and listen to birds. I walked back uphill and then felt a tickle on my ear which was my mouse, who had climbed up the back of my coat as I sat. The little mouse was quite fearless and I was sorely tempted to keep it as a pet, but it is often no favor to captivate wild animals, and so I placed my mouse into a pile of Douglas fir cones and then strode quickly away, although I spend the day looking over my shoulder. It’s a big dangerous world for young mice and only a few will make it through the summer.



Deer mouse Peromyscus maniculatus

Identifying Features: Distinct boundary between white underside and brown top, tail white underneath, brown on the top.

This is perhaps one of the most numerous animals in our area, yet few people ever see them. They are found in all habitats from the sandy beaches of the ocean to mountain alpine meadows, although they are most numerous in forests. They eat a wide variety of foods including seeds, fungi, berries, and plant material. They also chew fallen bones, antlers and skulls to get the calcium. Deer mice will have their first brood in February, and a female can breed again within days of giving birth and can have up to 5 litters of young in a year. Each litter is typically 4-5 young but if food resources are plentiful she may have up to 9. Her first litters of young can also have litters in that same year and so if food supplies were without limit, one mouse could produce hundreds.

Deer mice make nests of moss, grass or other soft plant material on dry, well-drained areas. Each nest is only used once then abandoned, and these empty nests are sought after by bumblebee queens in the spring who renovate the mouse nest and use it to raise their own young.

This small animal is a prime food item for all the local predators and they are readily consumed by weasels, hawks, owls, coyotes and even crows.



So I am caught up in the sweet world of nature that Rob has offered to me. I am thinking of The Tale of Despereaux, the heroic mouse that reminds me of Harry…
And then I imagine my sister, Barbara, reading this blog entry with eyes wide with the fear of germs, diseases. Am I crazy? Yes I might be. So I type in a google search for Deer Mice and immediately an option comes up for Deer Mice Diseases that I had previously ignored. I was thinking about ticks and how baby ticks feast on mice first and then grow to more ambitious meals of deer and us. This site doesn’t even mention ticks. Suddenly the world Rob has created transforms into a much more ominous vision with none of Rob’s writing flair.

First some mouse facts from Pest Control Canada


Mouse Facts

* Mice travel over their entire territory daily, investigating each change or new object that may be placed there.
* Mice have poor vision, hence their activity patterns rely heavily on smell, taste, touch, and hearing.
* Mice use the long sensitive whiskers near the nose and hairs on the body as tactile sensors. The whiskers and hairs enable the mouse to travel in the dark, adjacent to walls in burrows.
* Mice also have an excellent sense of balance, enabling them to walk along telephone wires, ropes and similar thin objects.
* Mice are excellent jumpers, capable of leaping at least 12 inches vertically.
* Mice can jump against a flat vertical surface using it as a spring board to gain additional height.
* They can run up almost any vertical surface; wood, brick, weathered sheet metal, cables, etc.
* They can easily travel for some distance hanging upside down.
* Although they are good swimmers, mice tend to take to water only if left with no other alternative.
* Mice are basically nocturnal in nature.
* House mice breed throughout the year and can become pregnant within 48 hours of producing a litter.
* There are usually about 6 mice to a litter and females may produce as many as ten litters (about 50 young) per year.
* It takes 18 to 21 days for gestation, and 35 days for a mouse to mature. Most mice live anywhere from 15 to 18 months.
* They make their nests out of the same types of soft materials as rats, and as many as 3 females may use the same nest.
* They commonly nest in insulation in attics, also in stoves and under refrigerators.
* Mice do not travel far from their nest, about 12 to 20 feet.

This would explain how they mange to around in my kitchen.

And then they share the dangers of feeding the birds (Is nothing safe?):

The most common rodent attractant in urban locations is wild bird seed. Once a constant food source has been detected, rodents will leave pheromone trails for their family members to follow. This could result in a large populations being attracted to your home or business. An abundant supply of food will also speed up their reproductive cycle. Most people who feed wild birds don't realize they are probably feeding more rodents than birds. Pet food, grass seed and poorly stored human food are other attractants.

And it gets worse. Ewww:

* In six months, one pair of mice can eat about 4 pounds of food and during that period produce some 18,000 fecal droppings.
* Deer mice are a primary vector of Hantaviral infections which cause hemorrhagic fevers.
* Mice may infect food with their droppings transmitting such organisms as salmonella and the microscopic eggs of tapeworms.
* Mice transmit disease in a number of ways including biting, infecting human food with their droppings or urine, indirectly via the dog or cat and bloodsucking insects.

The most common way mice transmit disease organisms is by contaminating food with their droppings and/or urine. The most threatening organism spread by mice is Salmonella, a cause of food poisoning, spread via droppings. Other transmittable organisms include tapeworms via droppings, rat-bite fever via bites, infectious jaundice/leptospirosis/Weil’s Disease via urine in food or water, a fungus disease (Favus) of the scalp either by direct contact or indirectly via cats, plague and murine typhus via fleas, Rickettsial pox via the mite Liponyssoides sanguineus (Hirst), lymphocytic choriomeningitis via droppings, and possibly poliomyelitis (polio). Another problem is house mouse mite dermatitis which is caused by these mites when they feed on humans.


Harry is not looking as cute as he was before. And now they ruin the happy thoughts I have about our rodent relocation program by sharing that deer mice have an incredible ability to track back to their nest and can travel very large distances to do so. They conducted a large study tracking mice that they captured and released:


50% of deer mice in that study returned to their home sites (a short-grass prairie habitat).

The mice traveled 650 m to 1,980 m (mean 1,500 m) and had to cross a river and pass optimal habitat patches to reach their home sites. Deer mice with previous homing experience were more successful in returning home (100%) than inexperienced mice (60%) and faster in doing so. Teferi and Millar suggest that these deer mice were able to navigate in a direct route to their home sites. We released mice in locations where they had no direct route to the house; they had to follow a winding road, climb over rocky outcroppings nearly 17 m high, or otherwise surmount obstacles and dangers, such as predators.

Perhaps I should have the Damn Husband release Harry in Chester on his way to work. The country mouse visits the urban enclave.
Poor Harry