vive. On a good marsh it is gen- 

 erally possible to remove two-thirds 

 of the muskrats each trapping sea- 

 son and still reserve sufficient brood 

 stock for a sustained annual crop, 

 as muskrats are so prolific that it is 

 extremely difficult to overtrap them 

 during the comparatively short 

 legal season. 



The average number of muskrats 

 trapped on an acre of the best type 

 of Maryland marsh over a long 

 period is 4 or 5, and catches of up 

 to 10 animals to the acre under ex- 

 cellent trapping conditions have 

 been reported. A Cameron Parish 

 (Louisiana) marsh of 3,000 acres 

 yielded 68,656 muskrats in 1946-47, 

 or approximately 23 muskrats to 

 the acre. The marsh had to carry 

 30 to 35 animals to the acre to make 

 a catch of this size possible, and 

 represented an advanced case of 

 overpopulation. By the end of the 

 trapping season the better parts of 

 the marsh had been eaten out. 



The "yield per house" has been 

 found to be a much better indicator 

 of trapping efficiency than the 

 "yield per acre." An average of 2 

 muskrats to an occupied house is 

 considered good trapping in view of 

 the difficulties encountered in trap- 

 ping, fluctuations in weather and 

 tides, and movements of the ani- 

 mals. As a rule, an average of 2.5 

 muskrats per house can be removed 

 without jeopardizing the breeding 

 stock for the next season. 



Trapping success is dependent on 

 several factors : to a very great ex- 

 tent on prevailing weather condi- 

 tions that at times seriously hamper 

 the trapper, as well as the experi- 

 ence, energy, and reliability of the 



trapper. Each trapper should be 

 assigned sufficient territory to as- 

 sure him a reasonable and equitable 

 return, but the unit should be small 

 enough to permit thorough trap- 

 ping. In general, 150 acres of good 

 marsh is about all one man can trap 

 efficiently in a normal season. 

 Some years it may be necessary to 

 double this acreage and also resort 

 to spot trapping to attract the 

 trappers. 



Composition of the population 



From a management standpoint 

 it is highly desirable that the man- 

 ager of a muskrat marsh, should 

 know the proportions of mice, kits, 

 subadults, and adults removed dur- 

 ing the trapping season. It is from 

 this information that he can deter- 

 mine the successfulness of the pre- 

 vious breeding season and the rate 

 of survival of the young. An ab- 

 normally high catch of adults indi- 

 cates little breeding during the pre- 

 vious season or a poor rate of sur- 

 vival of the young-of-the-year. An 

 abnormally low proportion of 

 adults indicates very close trapping 

 or overt rapping in either the pre- 

 vious or the current year. Size is 

 generally used to separate subadults 

 from the adults, but alone it is not 

 entirely reliable — there is consider- 

 able overlapping of weights and 

 measurements in the two groups. 

 Young individuals from better hab- 

 itats are often larger and heavier 

 than older animals from poorer 

 areas. A combination of characters 

 such as weight, length, thickness of 

 skin, pelage or fur quality, and 

 toughness in skinning, should be 

 considered in determining age 



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