284 Department of Conservation of Louisiana 



first step in the construction of a new house. The approach develops 

 into the plunge hole and the feeding platform forms the basis for 

 the inside of the house, which is then built up and around the plunge 

 hole. The muskrats here make use of the old houses, so much so that 

 most of the occupied houses are made over from the previous year 

 and eveTi the year before. 



"The materials used are those closest at hand and include the green 

 vegetation interspersed with muck. Houses indicate that building is in 

 progress by the bunches of fresh material dragged up onto the house 

 during the night. The building material is carried, dragged or pushed 

 while the muskrat still holds it in its mouth. It is placed in a seem- 

 ingly haphazard manner, yet a well-packed, matted roof results. This 

 mixture of muck and vegetation, which is always wet, except for the 

 sun-baked outer layer, forms a veritable thermos bottle. In the hottest 

 of weather the inside maintains a cool, even temperature, while dur- 

 ing the coldest snaps the warmth from the body heat of the muskrats 

 is kept constant. 



"The size of the house varies. Some are quite small, only a foot 

 high and a foot in diameter at the base, while others may be as large 

 as three to lour feet high and eight to ten feet in diameter. Usually, 

 the small houses are made by a single rat, perhaps the male, while 

 the larger ones are built by more than one rat, perhaps a pair. It 

 has been our experience that a single male, placed in a pen, will build 

 only a small house with a single nest, but when a female is placed 

 with him, they both work until the house is greatly enlarged. As the 

 size of the houses varies, so does the number of houses to a given area, 

 for naturally some areas contain more rats than others. In many 

 regions, even though the marsh vegetation is thick and water plenti- 

 ful no hills occur, while in other places hills may be as frequent as six 

 to an area of 20 by 50 feet. 



The number of hills to an area is usually the means of telling how 

 good a piece of rat land it is. It is assumed by trappers that houses 

 with many nests contain many rats. Houses have been found with 

 as many as seven nests, with plunge holes easily accessible. Only an 

 approximate estimation of the number of rats which occupy a house 

 can be made. From field observations, it appears that when breeding 

 is in progress but one pair of rats occupy a hill. During other seasons, 

 the inhabitants may vary in number. 



"In digging canals or runways, the muskrat digs with its front feet, 

 casting the material up between its hind legs. Then, taking a step 

 forward, it pushes the material farther out with its hind feet. This 

 is done on the surface, as well as underground. 'Marshlands which 

 harbor muskrats are netted with runways, both on the surface and 

 underground. When walking through the marsh one is constantly 

 sinking into these runways, which often form regular labyrinths. The 

 under ground runways are often quite deep, measuring in some cases 

 as deep as 16 inches. During the hot, dry summers, the openings to 

 these are often plugged mith muck to preserve the moisture. 



ASSOCIATIONS WITH OTHER ANIMALS 



"Muskrats are not the only animals which occupy muskrat houses. 

 The damp, warm house material harbors ants and other insects, 

 skinks, frogs, toads and snakes. The snakes include the small garter 

 snake and the southern king snake, which have been found during 

 cold weather under the top layers of material. 



"Moccasin snakes and blue runners have often been seen basking 

 on top of the muskrats' houses. Skinks (Leiolopisma laterale) 80 are 



'"Identified by G. K. Noble of the American Museum. 



