TY - JOUR
AU1 - Hibbard, Edmund, A.
AB - The determination of the age of mink by use of the baculum has been discussed by Elder (Jour. Mamm., 32: 43–50, 1951) and Petrides (Amer. Midl. Nat, 43: 355–382, 1950). However, there is little information in the literature on age ratios obtained from wild mink populations by the use of this method. The only comparable information I have found is given by Lechleitner (Jour. Mamm., 35: 496–503, 1954) who found an age ratio of 28.5 adults per 100 young in 153 wild males from Montana. He states that the morphology of the baculum was reliable in all cases for distinguishing juvenile and adult age classes. The present study began during the 1953 North Dakota trapping season when a small number of penis bones were obtained by examining discarded mink carcasses found at fur houses. The high percentage of fur bearers bought “in the round” in this state makes the procurement of mink carcasses quite easy. In 1954 and 1955 an attempt was made to obtain a larger sample. One method used was to ask the fur buyers to save mink carcasses. Piles of these carcasses were examined whenever possible and the penis bones were removed. Some of the more cooperative fur buyers helped in this collection by asking their skinners to remove this bone at the time the mink were skinned. This collection took place during the mid–November to December 31 trapping seasons. Bacula obtained from the various fur houses were cleaned by the use of dermestid beetles. Separation of the bones into two age classes was then readily accomplished by examining the basal portions, which in adults are encircled near the end by an obvious ridge and are much more massive in appearance than bones from young animals. Of the 2,080 penis bones examined, nearly all were readily separable into two age classes. There was some doubt on the age class involved in only six or seven individuals. These were bones which to all appearances were from juvenile animals but which were beginning to develop a dorsal protuberance. However, since none of these bacula showed the massive feature characteristics of adults, all were consigned to the juvenile class. Data on the age ratios of mink obtained during the three years is presented below. Area . No. in 1953 . Yg.–Old Ratio . No. in 1954 . Yg.–Old Ratio . No. in 1955 . Yg.–Old Ratio . Dickinson–Hettinger ………. — — 195 4.57:1 40 4.71:1 Minot ………. — — 432 4.27:1 400 5.55:1 Jamestown–Valley City ………. — — 508 3.58:1 409 4.84:1 Statewide ………. 96 4.32:1 1135 3.98:1 849 5.15:1 Area . No. in 1953 . Yg.–Old Ratio . No. in 1954 . Yg.–Old Ratio . No. in 1955 . Yg.–Old Ratio . Dickinson–Hettinger ………. — — 195 4.57:1 40 4.71:1 Minot ………. — — 432 4.27:1 400 5.55:1 Jamestown–Valley City ………. — — 508 3.58:1 409 4.84:1 Statewide ………. 96 4.32:1 1135 3.98:1 849 5.15:1 Open in new tab Area . No. in 1953 . Yg.–Old Ratio . No. in 1954 . Yg.–Old Ratio . No. in 1955 . Yg.–Old Ratio . Dickinson–Hettinger ………. — — 195 4.57:1 40 4.71:1 Minot ………. — — 432 4.27:1 400 5.55:1 Jamestown–Valley City ………. — — 508 3.58:1 409 4.84:1 Statewide ………. 96 4.32:1 1135 3.98:1 849 5.15:1 Area . No. in 1953 . Yg.–Old Ratio . No. in 1954 . Yg.–Old Ratio . No. in 1955 . Yg.–Old Ratio . Dickinson–Hettinger ………. — — 195 4.57:1 40 4.71:1 Minot ………. — — 432 4.27:1 400 5.55:1 Jamestown–Valley City ………. — — 508 3.58:1 409 4.84:1 Statewide ………. 96 4.32:1 1135 3.98:1 849 5.15:1 Open in new tab The sample collected in 1953 is perhaps too small to be representative but the samples from 1954 and 1955 should be sufficiently large. Bacula were collected from approximately 7 per cent of the animals harvested in 1954. While harvest figures for 1955 have not yet been determined, it is felt that at least a 15 per cent sample was secured. The difference in age ratios for the last two years is perhaps due to the small amout of trapping done during the 1955 season. Heavy snows and thick ice prevailed over much of the state that fall and prevented trappers from taking a normal harvest. The resultant low trapping pressure probably tended to take a much higher per cent of the younger, easier-to-catch animals. This was especially true in the northern part of the state where the weather conditions were most severe. This area, represented by the 1955 Minot data, showed the highest age ratio in the state. These figures show that each year the bulk of the trapping pressure falls on the young animals. In years when the pressure is light, such as in 1955, there is a higher survival of all animals and the next spring's breeding stock is increased accordingly. Thus one should expect a lowered age ratio among mink harvested in a year of normal trapping pressure following a year such as 1955. This paper is a contribution from Pittman-Robertson Project W 36 R of the North Dakota Game and Fish Dept. 1957 American Society of Mammalogists
TI - Age Ratios in Wild Mink Populations
JF - Journal of Mammalogy
DO - 10.2307/1376244
DA - 1957-08-23
UR - https://www.deepdyve.com/lp/oxford-university-press/age-ratios-in-wild-mink-populations-1fZrmt7DAO
SP - 412
EP - 413
VL - 38
IS - 3
DP - DeepDyve
ER -