IN UTERO PREGNANCY RATE, TWINNING RATE AND FETUS PRODUCTION FOR AGE-GROUPS OF COW MOOSE IN SOUTH-CENTRAL ALASKA
The relationship of reproductive parameters (i.e., pregnancy rate, twining rate and fetus production) to 5-age groups (calf = C, yearling = Y, teen = T, prime = P, and senior = S) of cow moose (Alces alces) were investigated. Age-class and in utero fetus counts from 895 moose killed in 14 area-specific antlerless/cow-moose hunts (year/area (Y/A) samples) during November-February, 1964 to 1974, in south-central Alaska were analyzed. Measures of central tendency and dispersion were used to characterize the reproductive parameters in each age-group classification. There was evidence of age-group effects on pregnancy rate (P = 0.0000). None of the C moose examined carried a fetus(es). Age-groups ordered by pregnancy rate were Y < T < S < P. The difference in pregnancy rate between P and S age-groups was not statistically significant (P = 0.1019). Y/A effects on pregnancy status were insignificant (P = 0.8414). There was evidence of age-group effects (P = 0.0001) and Y/A effects (P = 0.0001) on occurrence of twinning. None of the Y age-group moose examined carried twin fetuses. Age-groups ordered by twinning rate were T < S < P. The difference in twinning rate between T and P age-groups was statistically significant (P= 0.05). Age-groups ordered by fetus production (fetuses/100 cows) were Y < T < S < P. Based on the reproductive parameters studied, cow moose attain their maximum productivity after 3-years-of-age. Findings emphasize the importance of considering cow moose reproductive maturity in measuring productivity, interpreting information on productivity, modeling moose population dynamics and implementing selective harvests of cow moose.
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