Sex Ratio and Weights of Muskrats from the Montezuma National Wildlife Refuge

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Abstract
Approx. 800 acres of marsh on the Montezuma Natl. Wildlife Refuge in New York, trapped Jan. 1 to Mar. 20, 1944, by 3 trappers, yielded 3,919 muskrats, 2,152 (55%) [male][male] and 1,767 [female][female], a sex ratio of 122:100. The preponderance of [male][male] was maintained throughout the trapping operations. Males were heavier than [female][female], averaging 3.6 pounds (1,644 gms.) and 3.3 lbs. (1,503 gms.), respectively, the difference being highly significant statistically. The combined average wt. was 3.5 lbs. (1,588 gms.), the highest yet recorded for this species. The smallest weighed 1 lb. 4 oz.; the largest, a [male] trapped Jan. 29, weighed 5 lbs. 4 oz., a record for the species. Its measurements in inches were: body, 141/2; tail, 103/4; right hind foot, 37/16; greatest width of tail, 15/8. The relatively huge wts. of the Montezuma muskrats can be partly accounted for by the large amt. of fat as a result of excellent food and water conditions. From some of the larger muskrats about 8 oz. of fat was removed from the pelt, body and viscera. Accurate comparisons between wts. of muskrats from different sections of the country cannot be made, therefore, unless the amt. of fat is considered. Examinations of numerous feeding shelters showed that the favorite muskrat food on this Refuge in winter was the tender, partly green, growing shoots of the "blue flag" cattail (Typha angustifolia var. elongata) and the main roots of both cattail and burreed (Sparganium eurycarpum). These young shoots start in late autumn but remain 4-5 inches in length, beneath the ice, until spring. They are undoubtedly a most valuable source of essential nutrients.

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