Birth sex in an expanding black rhinoceros (<i>Diceros bicornis minor</i>) population

Law, Peter R.; Fike, Brad; Lent, Peter C.

doi:10.1644/13-mamm-a-175

Cited by 9 publications

(18 citation statements)

References 52 publications

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“…The climate of the study area is warm temperate (Fike 2011) with rainfall expected to be the main driver of environmental influence on dynamics. Yet, we (Law et al 2013(Law et al , 2014 found no evidence for the influence of rainfall on interbirth intervals, age at first reproduction, or birth sex, consistent with our estimation of no environmental stochasticity.…”

Section: Discussionsupporting

confidence: 81%

“…Few estimates of demographic stochasticity have been reported for mammals. This paper extends the study of a key population of the critically endangered black rhinoceros (Lent and Fike 2003;Ganqa et al 2005;Ganqa and Scogings 2007;van Lieverloo et al 2009;Fike 2011;Law et al 2013Law et al , 2014 and contributes to the understanding of megaherbivore population dynamics (Cromsigt et al 2002;Gough and Kerley 2006;Chamaillé-Jammes et al 2008;Okita-Ouma et al 2010;Owen-Smith 2010;Brodie et al 2011;Lee et al 2011;Okita-Ouma 2014) both for theoretical ecology and conservation science.…”

Section: Communicated By H Kierdorfmentioning

confidence: 63%

“…Direct examination of the structured population trajectories and matrix projections (Table 3) indicated that the discrepancies could largely be attributed to deviations between the actual numbers of and model projections of sex-specific recruitment each year. We previously (Law et al 2013(Law et al , 2014 found no deterministic explanation for the variation in interbirth intervals or birth sex in the SKKR population and proposed that the variation was due to demographic stochasticity.…”

Section: Discussionmentioning

confidence: 97%

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Dynamics of an expanding black rhinoceros (Diceros bicornis minor) population

Law

Fike²,

Lent

2015

Eur J Wildl Res

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Understanding population dynamics is critical for meta-population management, especially of endangered species, and also for megaherbivore ecology. We employed complete individual life records to construct census data for a reintroduced black rhinoceros population over 22 years since its founding and investigated its dynamics. Akaike's information criterion applied to scalar models of population growth based on the generalized logistic unambiguously selected an exponential growth model (r=0.102±0.017), indicating a highly successful reintroduction. No evidence of density dependence was detected, and thus, we could not confirm the threshold model of density dependence that has influenced black rhinoceros meta-population management. Our analysis supported previous work contending that the generalized logistic is unreliable when fitted to data that do not sample the entire range of population sizes. A stage-based matrix model of the exponential population dynamics exhibited mild transient behaviour. We found no evidence of environmental stochasticity, consistent with our previous studies of this population that found no influence of rainfall on demographic parameters. Demographic stochasticity was present, principally reflected in annual sex-specific recruitment numbers that differed from deterministic predictions of the matrix model. Demographically driven process noise should be assumed to be a component of megaherbivore population dynamics, as these populations are typically relatively small, and should be accounted for in managed removals and introductions. Increase in age at first reproduction with increasing population size, as manifested in the study population, may provide a warning of possible density feedback prior to detectable slowing of population growth rate for megaherbivores.

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Section: Discussionsupporting

confidence: 81%

Section: Communicated By H Kierdorfmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 97%

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Dynamics of an expanding black rhinoceros (Diceros bicornis minor) population

Law

Fike²,

Lent

2015

Eur J Wildl Res

Self Cite

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“…These data, rounded to the nearest 0.05, are listed in Table 1, along with the estimate that females in this region produce 0.315 calves per female per year. The female sex ratio used is 0.6, based on estimates reported in Law, Fike, & Lent, 2014, and the male maturity age is taken to be 2 (age 6 + -9). These data, when used in a 9-age class, female only Leslie matrix model yield a density-independent growth rate of 6.4% per annum (see SI Appendix 2).…”

Section: Basic Population Parametersmentioning

confidence: 99%

A web app for population viability and harvesting analyses

Getz

Muellerklein

Salter

et al. 2016

Natural Resource Modeling

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Population viability analysis (PVA) is used to assess the probability that a biological population will persist for a specified period of time. Such models are typically cast as Markov processes that may include age, stage, sex and metapopulation structures, density‐dependence and ecological interaction processes. They may also include harvesting, stocking, and thresholds that trigger interventions. Here we present a PVA web app that includes extensible user‐selected options. Specifically, this PVA web app allows for the specification of one to ten age classes, one or two sexes, single population or metapopulation configurations with 2 or 3 subpopulations, as well as density‐dependent settings for inducing region‐specific carrying capacities. Movement among subpopulations can be influenced by age, metapopulation connectivity, and attractivity of regions based on the relative fitness of the youngest age classes in each region. Simulations can be carried out deterministically or stochastically, with a user‐specified combination of demographic and environmental processes. This PVA web app is freely available at http://www.numerusinc.com/webapps/pva for running directly on any browser and device. It is easily modified by users familiar with the NovaModeler Software Platform.

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“…It is only recently that studies of black-rhinoceros demography have progressed much beyond natural history. Notable examples include Cromsigt et al (2002), Hrabar and du Toit (2005), Okita-Ouma et al (2009), Brodie et al (2011), Ferreira et al (2011, and Law et al (2013Law et al ( , 2014Law et al ( , 2015.…”

Section: Introductionmentioning

confidence: 99%

Intriguing density dependence but problematic birth rates in Greaver et al.’s study of a black-rhinoceros population

Law

Linklater

Gedir

2016

Preprint

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Greaver et al. (2014) presented evidence for density dependence in the Ithala population of black rhinoceros. Finding that they did not place their regression-based evidence in a modelling context, we recast their result as an example of the ramp model of density dependence that underlies black rhinoceros meta-population management. Greaver et al. concluded that the Ithala population did not reach carrying capacity, a conclusion we consider unwarranted since they did not conduct any analyses of trends in demographic parameters with population density. Our interpretation implies that the Ithala population did indeed reach carrying capacity. Where relevant, we compared their results for the Ithala population with those for another southern African black-rhinoceros population in order to provide a broader basis for evaluating black rhinoceros demography. We detail inconsistent presentation of data in their paper that plagued our efforts to understand their results and also draw attention to possible errors in some analyses. In particular, we argue that the results on birth rates reported by Greaver et al. appear dubious. Greaver et al. have presented important evidence for density dependence in a population of black rhinoceros but we suggest they have underutilized their data in interpreting this density dependence while misanalysing birth data.

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Birth sex in an expanding black rhinoceros (Diceros bicornis minor) population

Cited by 9 publications

References 52 publications

Dynamics of an expanding black rhinoceros (Diceros bicornis minor) population

Dynamics of an expanding black rhinoceros (Diceros bicornis minor) population

A web app for population viability and harvesting analyses

Intriguing density dependence but problematic birth rates in Greaver et al.’s study of a black-rhinoceros population

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