Examination of Annual Variation in the Adult Sex Ratio of Pronghorn (Antilocapra americana)

The adult sex ratio (ASR) is an important component of a population's demographics and can be used as an indicator of a population's status. However, the causes of annual variation in ASRs are unknown for many species. Fluctuations in ASR can arise through demographic stochasticity and int...

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Bibliographic Details
Published in:The American midland naturalist 2012-10, Vol.168 (2), p.289-301
Main Authors: Hoffman, Justin D, Genoways, Hugh H
Format: Article
Language:English
Subjects:
adults
Animal populations
Animal reproduction
Annual variations
Annuals
Antilocapra americana
Birth
bucks
Data processing
Demographic aspects
demographic statistics
Demography
fawns
Females
Habitats
Harvesting
Hunting
Hunting seasons
Males
Mating behavior
Mating systems
Modeling
Polls & surveys
Population density
Population growth
Population status
Precipitation
Pronghorn antelope
Ratios
Research s
Sex ratio
Snow
Stochasticity
Studies
Survival
Tablelands
Variables
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Summary:The adult sex ratio (ASR) is an important component of a population's demographics and can be used as an indicator of a population's status. However, the causes of annual variation in ASRs are unknown for many species. Fluctuations in ASR can arise through demographic stochasticity and intense selective harvesting. In this study we investigate the long-term patterns of variation in the ASRs (bucks: 100 does) for four populations of pronghorn (Antilocapra americana) in western Nebraska. We used multiple variables in a model selection process to predict annual fluctuation of pronghorn ASRs. We found that the number of bucks: 100 does significantly varied over the four populations. The best predictors of annual variation in pronghorn ASRs were variable across all populations. The number of pronghorn bucks harvested in the previous year's hunting season and the previous year's density of pronghorn were the most common predictors of ASR fluctuation. Buck harvest was an important predictor variable in only two of the four populations. Variation of harvest strategies within the populations could account for the lack of importance of buck harvest in half of the populations. The relationship between density and ASR is novel but difficult to interpret due to lack of data on birth sex ratios and fawn survival. More data on pronghorn demographics are needed in order to better explain the connection between density and ASR.
ISSN:0003-0031
1938-4238
DOI:10.1674/0003-0031-168.2.289