Biology ETDs


Pamela Cotton

Publication Date



The adult sex ratio and the sex ratio at birth was determined for the unhunted mule deer (Odocoileus hemionus) population occupying the riverbed area of the Bosque del Apache National Wildlife Refuge, Socorro County, New Mexico. The adult sex ratio was computed as the number of yearling and adult males per number of yearling and adult females observed within the effective area of seven linear one-mile transects established on the study area in accordance with the Stake Estimator Technique (Evans 1975). The ratio of 586 males:501 females (117:100) was significantly different from a 50:50 ratio. No evidence was found for differential dispersal of marked male and female deer. While accidents and disease could have contributed to a higher differential mortality of females, the male-biased adult sex ratio may have been the result of differential predation. Male deer on the study area were significantly heavier than females. Because of this size differential, predators on the study area may take female deer more frequently than males. Furthermore, male deer on the refuge, significantly heavier than male deer on six other deer study areas in New Mexico, may exceed the size of prey their predators are usually able to capture. The sex ratio at birth was determined by the examination of: 1) 20 fetuses collected during the last two months of pregnancy, 2) six fawns captured alive, and 3) one newborn fawn found dead. The ratio of 9 males:18 females, marginally significantly different from a 50:50 ratio, indicated a trend toward the production of more female fawns than male. Nutritional condition, as measured by rumen protein analysis, deer weights, and endogenous fat indices, was excellent. These results are consistent with sex ratios reported in the deer literature, but do not support the Trivers-Willard model for adaptive sex ratio adjustment.



Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Norman J. Scott

Second Committee Member

W. Evans

Third Committee Member

J. David Ligon

Fourth Committee Member

James Smith Findley

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Biology Commons