286 Department of Conservation of Louisiana 



"With scissors, first cut the leg off where the bone is broken. Then 

 with a very fine saw, saw the bone as far above, where the flesh is cut r 

 as possible in order that the muscles can grow over. A clean cut is 

 necessary, as sharp points on the bone cause pus to accumulate later. 

 It is then washed with Dakin's solution. With a needle and thread, two- 

 or three stitches are taken to pull the skin together over the end of the 

 bone. All this should be done as quickly as possible and as little blood 

 lost as possible. The ether cap is removed and the muskrat placed in a 

 box on clean grass or excelsior. 



"A small pan of water in which a little of Dakin's solution has been 

 placed is put in the box, which is then covered so that it is semi- 

 dark, but also provided with a circulation of air. In a few hours, if 

 the operation has been successful, the muskrat is recovered and ready 

 to eat. It may be kept in a small cage and fed corn, apple and green 

 food until the leg has healed. The pan of water should always contain 

 a small amount of antiseptic in order that the wound can heal easily 



BREEDING 



'Although we have found mice or embryos every month of the year, 

 the heaviest breeding takes place from November to April, inclusive. 

 During the trapping season of 1925-26, 600 muskrat carcasses were 

 examined. Of these 323 were females and 41, or 12%, contained em- 

 bryos. 



"During the 1926-27 season 263 carcasses were examined, of which 

 S9 were females, and of these 21% to 23% contained embryos. After 

 the trapping season closes in February there is generally high water 

 in the marshes until about the end of April. During these spring 

 months the rats, now undisturbed by trapping, are very active. Mice 

 can be found in most of the houses during these months. Although 

 the evidence for an extensive breeding season is conclusive, yet the 

 number of times one individual lemale breeds annually is by no maens 

 so frequent. One female, for instance, had a litter of young last 

 November and, as yet, has had no more. There is, however, every 

 indication that another litter will appear soon, as this pair has been 

 very active lately, building on their house and making new nests. 

 The period of gestation is more speculative material, according to- 

 literature, and by analogy with the gestation period of Microtus, it 

 has been placed at twenty-one days. We have, however, three females 

 which were seen to mate and twenty-one days have passed without 

 young being produced. 



"The number of embryos contained in 66 female carcasses varied 

 from one to six — three and four occurring with, by far, the greatest 

 frequency, thus making an average of between three and four to a 

 litter. In 17 litters of mice found in the field, the numbers ranged 

 from one to five — one, two and three occurring most frequently. This 

 seems to indicate mouse mortality. 



"Young mice, weighing only 21 grams, have been found in the nest, 

 blind and hairy. Large embryos have a sparse covering of hair, which 

 is distinctly visible. The sex can be determined easily before the eyes 

 open and the hair on the bellies become too thick to distinguish the 

 mamae. The mamae range in number from eight to ten. Out of. 

 213 adult and sub-adult female pelts examined, the following had: 



8 mammae, 2 — 2 pectoral, 2 — 2 inguinal 177 



9 mammae, 3 — 2 pectoral, 2 — 2 inguinal 32 



10 mammae, 3 — 3 pectoral, 2 — 2 inguinal 3 



9 mammae, 2 — 2 pectoral, 3 — 2 inguinal 1 



