Demography in relation to population density in two herbivorous marsupials: testing for source?sink dynamics versus independent regulation of population size

Johnson, Christopher N.; Vernes, Karl; Payne, Alison

doi:10.1007/s00442-004-1781-2

Cited by 11 publications

(7 citation statements)

References 33 publications

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“…Our estimated densities were much lower than those recorded in wetter areas, east of the great dividing range in the Townsville region, but huge variation in densities have been recorded in relation to soil fertility (Johnson, Vernes & Payne, 2005). The home range of rufous bettongs is also highly variable, from 15 to 107 ha, suggesting that at our 1041 ha study location there was likely home range overlap between the 46 individuals we marked (Frederick & Johnson, 1996;Johnson et al, 2005). In 2015, the driest year of the study, breeding was not observed and estimated survival rates were low.…”

Section: Discussioncontrasting

confidence: 86%

Heavy livestock grazing negatively impacts a marsupial ecosystem engineer

Neilly

Schwarzkopf

2018

Journal of Zoology

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Ecosystem engineers play an important role in resource availability and can be negatively impacted by anthropogenic disturbances, such as livestock grazing. The decline of digging and burrowing mammals in Australia is partly attributed to agriculture, however little is known about their use of microhabitats, and thus, how they respond to different cattle grazing regimes. Here, we examine the response of a marsupial ecosystem engineer, the rufous bettong (Aepyprymnus rufescens) to cattle grazing strategies and vegetation types, and examine whether microhabitat selection is driving this response. We hypothesized that rufous bettongs would be negatively impacted by heavy cattle grazing due to their use of ground‐level microhabitat features. We conducted a mark‐recapture trapping survey among four grazing treatments and in two vegetation types (box and ironbark woodlands), at a 20‐year grazing trial in northern Australia. We modelled rufous bettong abundance in response to grazing treatment and vegetation type and determined microhabitat preference using Manly selection ratios. We found that rufous bettongs preferred ironbark and avoided heavy grazing. Thus, they avoided the areas of highest cattle utilization. On average, individuals preferred high grass and other terrestrial microhabitat variables of moderate complexity. Our results indicate that habitat selection is contributing to the response of a marsupial ecosystem engineer to different grazing strategies. Mammalian digging and burrowing ecosystem engineers should be a conservation focus on rangelands due to their positive influence on a suite of species, and their ability to potentially mitigate some of the negative impacts of cattle grazing on soil health.

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Section: Discussioncontrasting

confidence: 86%

Heavy livestock grazing negatively impacts a marsupial ecosystem engineer

Neilly

Schwarzkopf

2018

Journal of Zoology

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“…Several studies of Australian marsupials have found links between indices of quantitative habitat quality and density (Braithwaite et al . 1984; Johnson et al . 2005) but through the indirect link of foliar or soil nutrient levels rather than food abundance.…”

Section: Discussionmentioning

confidence: 99%

Habitat-dependent population regulation in an irrupting population of long-nosed bandicoots (Perameles nasuta)

Dexter¹,

Hudson²,

Carter³

et al. 2010

Austral Ecology

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We used isodars to analyse habitat-dependent population regulation by long-nosed bandicoots Perameles nasuta during an irruption and subsequent population crash in three habitats (heath, woodland and forest) at Booderee National Park, south-eastern Australia. Specifically, we aimed to see whether patterns of habitatdependent population regulation matched a priori estimates of quantitative and qualitative differences between habitats. We also tested if habitat preference changed between the increasing and decreasing phase of the irruption as predicted by the reciprocating dispersal theory. Quantitative differences in habitat quality were indexed by the relative abundance of the main food of long-nosed bandicoots (terrestrial invertebrates), while qualitative differences were indexed by the availability of refuge from predation (vegetation understorey density). One index of fitness, body weight, was highest in forest, and lowest in heath, suggesting an ideal despotic model of habitat selection. Over the entire course of the irruption, there was density-dependent habitat selection with forest and woodland both quantitatively superior to heath. This reflected the overall abundance of invertebrates with highest abundance in woodland and forest and less in heath. Isodar analysis also revealed that although forest was quantitatively better than heath and equivalent to woodland it was qualitatively poorer than either habitat. Heath had a higher density of understorey than woodland and woodland having a higher density of understorey than forest giving crossover population regulation. When the increasing and declining phase of the irruption were analysed separately, no habitat was quantitatively superior to any other during either phase. The lack of switching in preference between habitats from the increasing to the declining phase of the irruption and the virtual absence of any dispersal by adults, does not support the reciprocating dispersal hypothesis.

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“…Fox area (northern Queensland, Australia, see Fig. 1) found that over a 3‐year period both high‐ and low‐density populations showed little variation in size, similar rates of turnover and no evidence for net dispersal from high‐ to low‐density populations (Johnson et al . 2005).…”

Section: Introductionmentioning

confidence: 99%

Dispersal and population structure of the rufous bettong,Aepyprymnus rufescens(Marsupialia: Potoroidae)

2005

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Many species of herbivorous mammals declined to extinction following European settlement of inland Australia. The rufous bettong, Aepyprymnus rufescens (a macropodoid marsupial), is ecologically similar to many of these species. We used analysis of microsatellite markers to determine dispersal patterns and mating system characteristics in a cluster of local populations of A. rufescens , with the aim of gaining a better understanding of regional population dynamics in such species. Particularly, we asked whether the rufous bettong showed sourcesink dynamics, as Morton (1990) hypothesized that many mammals may have been made vulnerable to extinction through such processes. We compared populations separated by distances of up to 12 km, and detected significant genetic differentiation among local populations ( F ST = 0.016). Females displayed greater genetic structuring than males, suggesting that females dispersed over shorter distances or less frequently than males. Geographic distance was weakly related to genetic distance between populations suggesting some gene flow at this scale, and paternity assignment indicated that dispersal can occur over distances of up to 6.5 km. Our study populations varied widely in density, but density did not explain the pattern of genetic differentiation observed. These findings of significant structure among populations, some influence of distance on genetic divergence and that density explains little of the divergence among populations, suggested that source-sink dynamics did not play a large role among these populations. Variance in male mating success was low (maximum assigned paternity for an individual male was 14% of offspring). While data on multiple maternity were limited, roughly half of repeat maternity was assigned to the same male, suggesting that the mating system of the rufous bettong is not purely promiscuous.

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Demography in relation to population density in two herbivorous marsupials: testing for source?sink dynamics versus independent regulation of population size

Cited by 11 publications

References 33 publications

Heavy livestock grazing negatively impacts a marsupial ecosystem engineer

Heavy livestock grazing negatively impacts a marsupial ecosystem engineer

Habitat-dependent population regulation in an irrupting population of long-nosed bandicoots (Perameles nasuta)

Dispersal and population structure of the rufous bettong,Aepyprymnus rufescens(Marsupialia: Potoroidae)

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