Assessing the Population Performance of the Black Rhinoceros in Kruger National Park

Ferreira, Sam M.; Greaver, Cathy; Knight, Mike

doi:10.3957/056.041.0206

Cited by 46 publications

(63 citation statements)

References 36 publications

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“…Our estimate of the annual intrinsic rate of growth for the SKKR population (0.102±0.017) is at the high end of published values (Owen-Smith 1988;Knight et al 2001;Okita-Ouma et al 2010;Brodie et al 2011;Ferreira et al 2011;Greaver et al 2014), which are typically below 0.1. Our estimate is within theoretical expectations based on the scaling law r=1.5W −0.36 (Caughley and Krebs 1983), where W is the mean adult live weight in kilograms, 700-1400 for black rhinoceros (Owen-Smith 1988; 1000 kg yields r=0.125).…”

Section: Discussioncontrasting

confidence: 40%

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: Discussioncontrasting

confidence: 40%

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

Law

Fike²,

Lent

2015

Eur J Wildl Res

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“…Our estimate of the (annual) intrinsic rate of growth for the SKKR population of 0.102 ± 0.017 is at the high end of the range of published values with estimates typically below 0.1 (Owen-Smith, 1988;Knight et al 2001;Okita-Ouma et al 2010;Brodie et al 2011;Ferreira et al 2011;Greaver et al 2014); Cromsigt et al (2001) obtained r = 0.1 while Okita-Ouma et al's (2010) largest estimate was 0.086 ± 0.022. The scaling law r = 1.5 W -0.36 (Caughley and Krebs 1983), where W is mean adult live weight in kilograms, yields W = 1750 for r = 0.102 and higher rates for lower W, so the estimate of SKKR is within theoretical expectations as W lies in the range 700 -1400 for black rhinoceros (Owen-Smith, 1988; 1000kg yields r = 0.125).…”

Section: Discussionmentioning

confidence: 46%

Dynamics of an Expanding Black Rhinoceros (Diceros Bicornis Minor) Population

Law

Fike²,

Lent

2015

Preprint

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Population dynamics is a central component of demography and critical for meta-population management, especially of endangered species. We employed complete individual life records to construct census data for a reintroduced black rhinoceros population over 22 years from its founding and investigated that population's dynamics to inform black rhinoceros meta-population management practice and, more generally, megaherbivore ecology. 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, but yielding no evidence of density dependence. This result is consistent with, but does not confirm, the threshold model of density dependence that has influenced black rhinoceros meta-population management. Our analysis did support previous work contending that the generalized logistic is unreliable when fit to data that do not sample the entire range of possible 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. Process noise derived from demographic stochasticity, 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 considered in managed removals and introductions. We suggest that an extended period of exponential growth is common for megaherbivore populations growing from small size and that an increase in age at first reproduction with increasing population size, manifest in the study population, may provide a warning of density feedback prior to detectable slowing of population growth rate for megaherbivores .

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“…Density-dependant growth regulation in large-mammal populations may manifest through increased female age at first parturition or inter-calving intervals, or decreased immature or adult survival (Eberhardt, 2002). In the case of black rhino, these processes most likely occur as a result of socially mediated cues rather than resource limitation (Ferreira et al, 2011;Law et al, 2013), particularly in small reserves with higher rates of association (Linklater & Swaisgood, 2008). Recorded fighting mortalities in T2 and decreased male survival rates suggest that reduced adult male survival may be a contributing factor.…”

Section: Discussionmentioning

confidence: 99%

Starting small: long‐term consequences in a managed large‐mammal population

et al. 2018

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Small populations are vulnerable to founder effects, stochastic demographic events and inbreeding depression. These factors raise the extinction probability of small populations, and thus effective management plans for endangered species have become essential. The black rhinoceros (Diceros bicornis) survived a historic global population crash and is currently facing renewed threat through poaching, population fragmentation and isolation. South Africa is home to approximately 36% of the world's remaining black rhinos; however, this population is fragmented across parks and reserves, and many of these small populations remain geographically and genetically isolated. The historic population crash, subsequent fragmentation and relentless poaching pressure together threaten the viability of the black rhino population within South Africa. This study employed a practical, non‐invasive sampling protocol and genetic analyses to assess the growth and performance of a small founder population in a fenced reserve. We used these data and recorded life‐history data to compare the population growth and vital rates between the first and second 10‐year periods since founding. We report a decrease in population growth rate and male survival in the second 10‐year period (0.06; 0.89) compared to the first (0.09; 0.97). Genetic diversity (HEXP = 0.405) was low when compared to larger black rhino populations, and average pairwise relatedness was high (0.193). These results suggest that negative genetic consequences and the beginning of density‐dependant growth regulation may be present in this population. This highlights the importance of establishing an evaluation framework for the assessment of small populations of long‐lived mammals in order to inform metapopulation management.

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Assessing the Population Performance of the Black Rhinoceros in Kruger National Park

Cited by 46 publications

References 36 publications

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

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

Dynamics of an Expanding Black Rhinoceros (Diceros Bicornis Minor) Population

Starting small: long‐term consequences in a managed large‐mammal population

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