Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2011;6(11):e28002.
doi: 10.1371/journal.pone.0028002. Epub 2011 Nov 18.

Contrasting Life Histories in Neighbouring Populations of a Large Mammal

Affiliations
Free PMC article

Contrasting Life Histories in Neighbouring Populations of a Large Mammal

Tom H E Mason et al. PLoS One. .
Free PMC article

Abstract

Background: A fundamental life history question is how individuals should allocate resources to reproduction optimally over time (reproductive allocation). The reproductive restraint hypothesis predicts that reproductive effort (RE; the allocation of resources to current reproduction) should peak at prime-age, whilst the terminal investment hypothesis predicts that individuals should continue to invest more resources in reproduction throughout life, owing to an ever-decreasing residual reproductive value. There is evidence supporting both hypotheses in the scientific literature.

Methodology/principal findings: We used an uncommonly large, 38 year dataset on Alpine chamois (Rupicapra rupicapra) shot at various times during the rutting period to test these two hypotheses. We assumed that body mass loss in rutting males was strongly related to RE and, using a process-based approach, modelled how male relative mass loss rates varied with age. For different regions of our study area, we provide evidence consistent with different hypotheses for reproductive allocation. In sites where RE declined in older age, this appears to be strongly linked to declining body condition in old males. In this species, terminal investment may only occur in areas with lower rates of body mass senescence.

Conclusions/significance: Our results show that patterns of reproductive allocation may be more plastic than previously thought. It appears that there is a continuum from downturns in RE at old age to terminal investment that can be manifest, even across adjacent populations. Our work identifies uncertainty in the relationship between reproductive restraint and a lack of competitive ability in older life (driven by body mass senescence); both could explain a decline in RE in old age and may be hard to disentangle in empirical data. We discuss a number of environmental and anthropogenic factors which could influence reproductive life histories, underlining that life history patterns should not be generalised across different populations.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Patterns of male mass and mass loss with age.
Variation in mean predicted male chamois initial body mass (blue lines), final body mass (green lines) and body mass loss rate, L (red lines), with age across our three study sites; Adamello (A & D), Brenta (B & E) and Presanella (C & F). Predicted values for each age are mean values across all years. Dashed lines represent 95% confidence intervals from 1,000 bootstrapped replicates . Sample sizes are displayed for each age.
Figure 2
Figure 2. Patterns of female mass and mass loss with age.
Variation in mean predicted age of female chamois initial body mass (blue lines), final body mass (green lines) and body mass loss rate, L (red lines), across our three study sites; Adamello (A & D), Brenta (B & E) and Presanella (C & F). Predicted values for each age are mean values across all years. Dashed lines represent 95% confidence intervals from 1,000 bootstrapped replicates . Sample sizes are displayed for each age.
Figure 3
Figure 3. Age structure of males.
The abundance of males in each site at each age, from 6 years upwards (hunting age class I, see Table S1), relative to the area-wide age-distribution. Assuming that individuals within each hunting age class are shot randomly, the proportions of different ages shot represent the age structure of that class. A value of 0 indicates no difference to the mean population age-structure. Adamello is a young population relative to Brenta and Presanella.

Similar articles

See all similar articles

Cited by 5 articles

References

    1. Stearns SC. Oxford: Oxford University Press; 1992. The Evolution of Life Histories.
    1. Williams GC. Princeton, New Jersey: Princeton University Press; 1966. Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought.
    1. Williams GC. Natural Selection, The Costs of Reproduction, and a Refinement of Lack's Principle. Am Nat. 1966;100:687–690.
    1. Clutton-Brock TH. Reproductive effort and terminal investment in iteroparous animals. Am Nat. 1984;123:212–229.
    1. Pianka ER, Parker WS. Age-Specific Reproductive Tactics. Am Nat. 1975;109:453–464.

Publication types

Feedback