Mortality and female fecundity in an expanding black rhinoceros (Diceros bicornis minor) population

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

doi:10.1007/s10344-013-0694-y

Cited by 23 publications

(60 citation statements)

References 28 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%

“…It remains unclear, however, at what rate population growth declines when density feedback begins. We previously reported (Law et al 2013) an increase of age at first reproduction in SKKR with increasing population size despite no apparent resource limitation (van Lieverloo et al 2009) and suggested that this response may be socially mediated (Bronson 1989:163). Increase in age at first reproduction might therefore provide a practical early warning sign of density feedback in an expanding population of megaherbivores prior to detectable slowing in growth rate.…”

Section: Discussionmentioning

confidence: 91%

“…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%

“…The biological states of interest were calf (dependent upon the mother, specifically, in association with its mother, less than 4 years old, and no younger calf present), subadult (no longer a calf but not yet an adult), and adult (for females, have given birth or at least 7 years old; for males, 8 or more years old) (Law et al 2013;Law and Linklater 2014). Lacking paternity data, reproduction was assigned exclusively to females (Goodman 1969).…”

Section: Matrix Modelmentioning

confidence: 99%

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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: 91%

Section: Discussionmentioning

confidence: 97%

Section: Matrix Modelmentioning

confidence: 99%

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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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Effects of dehorning on population productivity in four Namibia sub-populations of black rhinoceros (Diceros bicornis bicornis)

et al. 2022

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The black rhinoceros (rhino) (Diceros bicornis) is critically endangered, with poaching being one of several threats to the species’ survival. Many reserves across several countries, including Namibia, South Africa, and Zimbabwe, now dehorn their rhinos in an attempt to reduce poaching. Historical data collected by the Namibian Ministry of Environment, Forestry, and Tourism and Save the Rhino Trust were used to investigate whether dehorning has an effect on age at first reproduction (AFR), inter-calving interval (ICI), birth sex ratios, calf survival, cause of death, and lifespan. These were assessed in four Namibian sub-populations (hereafter referred to as ‘populations’) of black rhino (denoted A, B, C, and D) which have undergone varying levels of dehorning. No significant difference was found in any of the variables between dehorned and horned individuals. Population was a significant predictor of AFR (LRT = 7.433, p = 0.024) and ICI (LRT = 13.281, p = 0.004), although pairwise comparisons only found populations A and B to be significantly different (AFR: z = −2.736, p = 0.017, ICI: z = −3.705, p = 0.001). Additionally, a significantly higher number of males than females were born in population D (p = 0.021, CI = 0.544, 0.960). The main cause of death across all individuals was poaching, although there was no significant difference in the proportion of rhinos poached between dehorned and horned individuals (X2 = 0.638, p = 0.424, n = 265). No evidence was found to suggest that dehorning has any effect on AFR, ICI, birth sex ratios, calf survival, or lifespan in the black rhino, which is reassuring in the continued use of dehorning as an anti-poaching technique in this species.

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Admixture and reproductive skew shape the conservation value of ex situ populations of the Critically Endangered eastern black rhino

Elsner-Gearing,

Kretzschmar,

Shultz

et al. 2024

Conserv Genet

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Small populations of endangered species risk losing already eroded genetic diversity, important for adaptive potential, through the effects of genetic drift. The magnitude of drift can be mitigated by maximising the effective population size, as is the goal of genetic management strategies. Different mating systems, specifically those leading to reproductive skew, exacerbate genetic drift by distorting contributions. In the absence of an active management strategy, reproductive skew will have long-term effects on the genetic composition of a population, particularly where admixture is present. Here we examine the contrasting effects of conservation management strategies in two ex situ populations of the Critically Endangered eastern black rhino (Diceros bicornis michaeli), one managed as a semi-wild population in South Africa (SAx), and one managed under a mean-kinship breeding strategy in European zoos. We use molecular data to reconstruct pedigrees for both populations and validate the method using the zoo studbook. Using the reconstructed pedigree and studbook we show there is male sex-specific skew in both populations. However, the zoo’s mean-kinship breeding strategy effectively reduces reproductive skew in comparison to a semi-wild population with little genetic management. We also show that strong male reproductive skew in SAx has resulted in extensive admixture, which may require a re-evaluation of the population’s original intended role in the black rhino meta-population. With a high potential for admixture in many ex situ populations of endangered species, molecular and pedigree data remain vital tools for populations needing to balance drift and selection.

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Mortality and female fecundity in an expanding black rhinoceros (Diceros bicornis minor) population

Cited by 23 publications

References 28 publications

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

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

Effects of dehorning on population productivity in four Namibia sub-populations of black rhinoceros (Diceros bicornis bicornis)

Admixture and reproductive skew shape the conservation value of ex situ populations of the Critically Endangered eastern black rhino

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