When is the birth rate the key factor associated with population dynamics?

Coulson, Tim; Hudson, Elodie; Holt, William V.; Pickard, Amanda R.; Rodger, John C.; Wildt, David E.

doi:10.1017/cbo9780511615016.010

Cited by 10 publications

(22 citation statements)

References 35 publications

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“…Third, there is little evidence that either of the previous generalizations (Gaillard et al . 2000; Coulson & Hudson 2003) is supported. Fourth, any decomposition of variation in population growth should consider covariation between demographic rates.…”

Section: Discussionmentioning

confidence: 74%

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Decomposing the variation in population growth into contributions from multiple demographic rates

Coulson

Gaillard

Festa-Bianchet

2005

Journal of Animal Ecology

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166

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Summary1. The decomposition of variation in population growth into the relative contributions from different demographic rates has multiple uses in population, conservation and evolutionary biology. Recent research has favoured methods based on matrix models termed 'life-table-response experiments' or more generally 'the retrospective matrix method', which provide an approximation of a complete demographic decomposition. The performance of the approximation has not been assessed. 2.We compare the performance of the retrospective matrix method to a complete decomposition for two bighorn sheep populations and one red deer population. 3. Different demographic rates make markedly different contributions to variation in growth rate between populations, because each population is subject to different types of environmental variation. 4. The most influential demographic rates identified from decomposing observed variation in population growth are often not those showing the highest elasticity. Consequently, those demographic rates most strongly associated with deterministic population growth are not necessarily strongly associated with temporal variation in population growth. 5. The retrospective matrix method provides a good approximation of the demographic rate associated most strongly with variation in population growth. However, failure to incorporate the contribution of covariation between demographic rates when decomposing variation in population growth can lead to spurious conclusions.

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Section: Discussionmentioning

confidence: 74%

“…The generalizations proposed by Gaillard et al . (2000) and Coulson & Hudson (2003) were based on studies that ignored covariation between demographic rates. Before any new generalizations can be proposed further studies examining the association between demographic rate covariation and variation in population growth are required.…”

Section: Discussionmentioning

confidence: 99%

Decomposing the variation in population growth into contributions from multiple demographic rates

Coulson

Gaillard

Festa-Bianchet

2005

Journal of Animal Ecology

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166

223

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“…Density dependence primarily in adult survival was previously noted also for African buffalo (Syncerus caffer) in Serengeti (Sinclair 1973), and zebra (Equus burchelli) and giraffe (Giraffa camelopardalis) in Kruger . The rise in adult mortality toward high density was largely an outcome of increased mortality among older females, coupled with a shift in population structure toward older animals, in populations where prime and old females could be differentiated (e.g., kudu, Owen-Smith 1990; red deer, Coulson and Hudson 2003;bighorn sheep, Festa-Bianchet et al 2003). Nevertheless, a density effect on mortality among prime-aged females was detectable for kudu, albeit more weakly.…”

Section: Density-related Patternsmentioning

confidence: 99%

“…This implies that variable juvenile survival is mainly responsible for causing population size to vary, as well as for densityrelated feedbacks restricting population fluctuations. However, these outcomes may be contingent upon the ecological circumstances (Owen-Smith and , and differ between phases of population growth (Coulson and Hudson 2003). Furthermore, the changing age structure of the population has additional effects on the realized population growth rate, with old animals having lowered survival forming a greater proportion as the net growth rate slows (Festa-Bianchet et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Demographic Determination of the Shape of Density Dependence for Three African Ungulate Populations

Owen‐Smith

2006

Ecological Monographs

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The shape of the relationship between population growth rate and population density has important consequences for population dynamics. Past reviews have led to suggestions that, for large mammalian herbivores, the density‐dependent response is curvilinear or abrupt in its onset above some threshold density, and that different demographic segments differ in their sensitivity to rising density. I examined the form of density dependence in stage‐specific mortality rates for three African ungulate populations for which data were available over a sufficiently wide range in abundance: kudu in Kruger National Park, South Africa, and wildebeest in both Kruger and Serengeti National Park, Tanzania. Calf losses remained fairly high toward low‐density levels, indicating that juvenile mortality was sensitive to various influences, some acting independently of density. The maximum population growth rate at low density was truncated by density‐independent factors restricting recruitment success, while the slope of the initial plateau region of the density‐dependent response depended on how steeply juvenile mortality rose and fertility in the youngest reproductive stage fell with increasing density. Adult mortality rose only above some threshold density, especially among older females, and was largely responsible for setting the zero growth level. The density‐dependent response in adult mortality was effectively linear, so that the trend in population growth rate toward the zero growth level was also linear. Differences in the stage of onset and steepness of the density dependence in adult female mortality appeared to be affected by differences in the predator–prey relationship for these three ungulate populations. Overall nonlinearity in the population growth response was an emergent outcome of the different stages at which mortality and recruitment losses among different population segments became affected. Models depicting curvilinear density dependence exaggerate the tendency toward overcompensation around the zero growth level and resultant propensity toward oscillatory dynamics. Reliable projections of population dynamics require models that are faithful to the intrinsic demographic responses determining the overall population growth rate.

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“…2 al. Prior to 1972 the population was limited by culling; during the period of population increase, the predominant limiting factor was the birth rate; but since the population reached ecological carrying capacity, the population has been food limited (Clutton-Brock et al 1985, Albon et al 2000, Coulson and Hudson 2003, with starvation being the predominant cause of death (Clutton-Brock et al 1997a). Prior to 1972 the population was predominantly limited by hunting, with an unselected ϳ14% of females and males removed annually (Clutton-Brock et al 1985, 2002, Milner-Gulland et al 2000.…”

Section: Introductionmentioning

confidence: 99%

The Demographic Consequences of Releasing a Population of Red Deer From Culling

Coulson

Guinness

Pemberton

et al. 2004

Ecology

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141

165

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A change in population density can generate spatial and demographic effects that can have an impact on fluctuations in population size for many years. Although the demographic effects of time lags have been incorporated into analyses of time series data, there are few detailed descriptions of the long-term demographic consequences of a change in density. We use detailed, individual-based data from a population of red deer (Cervus elaphus) from the North Block of the Isle of Rum, Scotland, to describe long-term demographic and spatial effects of a change in density. The population was released from hunting pressure in 1972. Over the following 10 years population density doubled and, since the early 1980s, has fluctuated around ecological carrying capacity. The cessation of culling led to long-term transient spatial and demographic effects that have persisted for 30 years. Different vital rates responded to the increase in density at different rates, causing long-term changes to the demographic and spatial structure of the population. These changes altered the impact of different age-and sex-specific vital rates on annual changes in population size. These changes are still ongoing, 30 years after cessation of the cull, suggesting that a change in density may generate transient dynamics that persist for several generations.

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When is the birth rate the key factor associated with population dynamics?

Cited by 10 publications

References 35 publications

Decomposing the variation in population growth into contributions from multiple demographic rates

Decomposing the variation in population growth into contributions from multiple demographic rates

Demographic Determination of the Shape of Density Dependence for Three African Ungulate Populations

The Demographic Consequences of Releasing a Population of Red Deer From Culling

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