Demographic vital rates and population growth: rethinking the relationship in a harvested elk population

Jonathan Conard,Philip Gipson

doi:10.1038/npre.2009.3609.1

Jonathan Conard, Philip Gipson

Open Access

https://doi.org/10.1038/npre.2009.3609.1

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Abstract

AbstractUnderstanding the nature of the relationship between demographic vital rates and the rate of population change (λ) is important for determining effective strategies for population management and conservation. We examined the relative impacts of various demographic vital rates on λ within the range of temporal vital rate variability observed in a harvested population to test the hypotheses that adult survival rates in ungulates are relatively invariant when compared to other vital rates and that variability in calf survival has a greater influence on rates of population change than adult survival. Vital rates were estimated for an elk (Cervus elaphus) population at Fort Riley, Kansas from October 2003 – February 2007. The magnitude of adult survival rates were similar to other harvested populations and models including a negative relationship between survival and age received the highest levels of support. Prime-age adult survival had the highest stage-specific elasticity values, indicating a high contribution of these matrix elements to λ. Life-stage simulation analysis indicated that variation in calf survival had the highest correlation with variation in λ (r^2^ = 0.61). Our results suggest that adult survival rates in harvested populations may experience increased levels of variability, but that calf survival rates have the greatest relative influence on λ due to the wider range of variability observed for this vital rate.

Highlights

Forlonglived vertebrates,adultsurvivalis generally the vitalrate w ith the higheststagespecific elasticityvalue
Itis im portantto determ ine ifthe relationship betw een observed vitalrates and rates ofpopulation change in sm all/harvested populations is consistentw ith the hypothesis thatadult survivalrates in ungulates are relatively invariantw hen com pared to other vitalrates (G aillard etal.1998,G aillard etal.2000),and thatvariability in juvenile survivalhas a greaterinfluence on λ than adultsurvival(R aithelet aMl.e2t0h0o7d).s
Lifestage sim ulation analysis results indicatedFtihg.a3t.thMeatgrirxeoaftevistatlarmateouenlatsoticfity vaalruieastion in λ w as explained by variation in calfsurvival(r2 = 0.606)and prim e age adultsurvival(r2 = 0.367)

Summary

Introduction

Forlonglived vertebrates,adultsurvivalis generally the vitalrate w ith the higheststagespecific elasticity (eij)value. H ow ever,adultsurvivalis relatively invariantin response to changes in environm entalconditions or population density (G aillard etal.1998,Pfister1998,G aillard etal.2000, Eberhardt2002). Forharvested populations,variation in harvestregulations,hunteraccess, and success rates could increase variability in adultsurvival.

Results

Conclusion