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Variation in gestation length among captive reindeer (Rangifer tarandus tarandus)
1Department of High Latitude Agriculture, School of Natural Resources and Agricultural Sciences, University of Alaska Fairbanks, Fairbanks, AK 99775-7200, USA. j.rowell@uaf.edu
Theriogenology
|April 7, 2009
Summary
Reindeer gestation length is negatively linked to conception date, enhancing calving synchrony. This relationship was confirmed in a 2-year study and a larger historical dataset, with male birth weight positively correlating with gestation length.
Area of Science:
- Reproductive biology
- Animal science
- Wildlife ecology
Background:
- Reindeer (Rangifer tarandus) exhibit highly synchronized mating and calving, with a notably variable gestation period (203-240 days).
- Previous research indicated a negative correlation between reindeer gestation length and conception date.
- Understanding factors influencing gestation length is crucial for managing reindeer populations and predicting calving events.
Purpose of the Study:
- To investigate the negative relationship between gestation length and conception date in reindeer using a controlled experimental design.
- To validate these findings with a larger historical dataset from established reindeer herds.
- To explore potential influencing factors such as dam weight, calf birth weight, and calf sex on gestation length.
Main Methods:
- A switchback design experiment over two years, dividing reindeer into early and late mating groups.
- Regression analysis was performed on paired observations (n=11) from the experimental groups.
- Analysis of a larger historical dataset (n=70) from University of Alaska Fairbanks reindeer herds, including conception dates verified by progesterone levels and recorded gestation lengths.
Main Results:
- A significant negative association (P<0.001) was found between gestation length and conception date in the experimental group (slope=-0.31).
- This negative relationship was confirmed in the larger historical dataset (P<0.001, slope=-0.37).
- Dam weight, calf birth weight, and calf sex were not significant predictors of gestation length, but male birth weight showed a positive relationship with gestation length in the larger dataset (r²=0.19, P=0.014).
Conclusions:
- The negative relationship between conception date and gestation length significantly enhances calving synchrony in reindeer.
- While the precise mechanisms and limits of this gestation plasticity remain unclear, photoperiod's role in early embryonic development is suggested.
- The findings contribute to understanding reproductive timing and synchrony in reindeer populations.
