Remove the annual crop of musk- 

 rats at the right time and in 

 amounts compatible with the 

 numbers present on the marsh. 



An estimate or census, should be 

 made each year, just before the legal 

 trapping season, as a basis for 

 planned removal of the surplus and 

 determination of population trends. 

 Muskrat crops- cannot be held over 

 a long period for harvesting in a 

 single season. Whenever their 

 density reaches one dwelling house 

 to an acre, trapping should be un- 

 dertaken. A density of 2.5 houses 

 an acre calls for immediate heavy 

 trapping; if action is delayed at 

 this time "eat-outs" invariably re- 

 sult in spite of intensive trapping 

 later. To maintain a proper bal- 

 ance between the muskrats and their 

 environment, approximately two- 

 thirds of the population should be 

 removed each year. 



Analyze the composition of the 

 catch made during the trapping 

 season. Sex ratios and distribution 

 of the age classes of the trapped ani- 

 mals provide an excellent index to 

 population trends. An abnormally 

 high take of adults indicates little 

 or no breeding that season or poor 

 survival of the young. A low pro- 

 portion of adults is indicative of 

 close trapping or overtrapping in 

 the preceding or current year. 



Select trappers carefully. Trap- 

 pers should be experienced, reliable, 

 and energetic. Trap lines should be 

 run daily, preferably early in the 

 morning. Knowledge of the habits 

 of the muskrat and suitable equip- 

 ment are necessary to efficient trap- 

 ping. 



Assign to a trapper only as much 

 acreage as he can manage; and 

 make the catch quota liberal 

 enough to avoid undertrapping. 



The "yield-per-house" is a much 

 better measure of trapping effi- 

 ciency than the "yield-per-acre." 

 Overtrapping can occur under some 

 situations, but it has been the ex- 

 perience of trappers and marsh- 

 owners generally that it is almost 

 impossible to overtrap a normal 

 muskrat population. It is far bet- 

 ter to overtrap an area than to un- 

 dertrap it. 



Keep populations of predators, as 

 foxes, raccoons, and minks within 

 reasonable limits. The annual 

 drain on the muskrat by predators 

 may become very serious. Their 

 control will lead to larger muskrat 

 crops and a reduction in the num- 

 ber of damaged pelts. By removing 

 such animals during the legal trap- 

 ping season additional revenue can 

 be realized from the sale of their 

 pelts. 



Drain "eat-outs'* promptly. To 



correct "eat-outs," drainage ditches, 

 usually about 30 inches wide and 

 deep, should be cut across the marsh 

 to carry the water from the de- 

 nuded areas. This permits the sun- 

 light to reach the mud bottom and 

 creates better conditions for seed 

 germination and the survival of any 

 pieces of rootstalks remaining. 

 Closed or blind ditches are pre- 

 ferred and should be so constructed 

 that salt-water intrusion is pre- 

 vented in coastal marshes. 



Use cattle grazing cautiously. In 



general, muskrats and cattle do not 



41 



