Directions in Conservation Biology

Caughley, Graeme

doi:10.2307/5542

Cited by 2,019 publications

(1,455 citation statements)

References 86 publications

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“…As such, each alien control programme should be designed and implemented as a scientific experiment, with hypotheses, rigorous protocols, and control of expected (and unexpected) results (Pascal & Chapuis, 2000). This will allow researchers in conservation biology to establish a wider and stronger theoretical framework, which is much needed in this discipline (Caughley, 1994), and will also allow conservation managers to benefit from ensuing generalisations.…”

Section: Discussionmentioning

confidence: 99%

Mammal invaders on islands: impact, control and control impact

Courchamp¹,

Chapuis²,

2003

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The invasion of ecosystems by exotic species is currently viewed as one of the most important sources of biodiversity loss. The largest part of this loss occurs on islands, where indigenous species have often evolved in the absence of strong competition, herbivory, parasitism or predation. As a result, introduced species thrive in those optimal insular ecosystems affecting their plant food, competitors or animal prey. As islands are characterised by a high rate of endemism, the impacted populations often correspond to local subspecies or even unique species. One of the most important taxa concerning biological invasions on islands is mammals. A small number of mammal species is responsible for most of the damage to invaded insular ecosystems : rats, cats, goats, rabbits, pigs and a few others. The effect of alien invasive species may be simple or very complex, especially since a large array of invasive species, mammals and others, can be present simultaneously and interact among themselves as well as with the indigenous species. In most cases, introduced species generally have a strong impact and they often are responsible for the impoverishment of the local flora and fauna. The best response to these effects is almost always to control the alien population, either by regularly reducing their numbers, or better still, by eradicating the population as a whole from the island. Several types of methods are currently used : physical (trapping, shooting), chemical ( poisoning ) and biological (e.g. directed use of diseases ). Each has its own set of advantages and disadvantages, depending on the mammal species targeted. The best strategy is almost always to combine several methods. Whatever the strategy used, its long-term success is critically dependent on solid support from several different areas, including financial support, staff commitment, and public support, to name only a few. In many cases, the elimination of the alien invasive species is followed by a rapid and often spectacular recovery of the impacted local populations. However, in other cases, the removal of the alien is not sufficient for the damaged ecosystem to revert to its former state, and complementary actions, such as species re-introduction, are required. A third situation may be widespread : the sudden removal of the alien species may generate a further disequilibrium, resulting in further or greater damage to the ecosystem. Given the numerous and complex population interactions among island species, it is difficult to predict the outcome of the removal of key species, such as a top predator. This justifies careful pre-control study and preparation prior to initiating the eradication of an alien species, in order to avoid an ecological catastrophe. In addition, long-term monitoring of the post-eradication ecosystem is crucial to assess success and prevent reinvasion.

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Section: Discussionmentioning

confidence: 99%

Mammal invaders on islands: impact, control and control impact

Courchamp¹,

Chapuis²,

2003

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“…This is a problem that has been the basis for criticism of PVA modelling by some authors (e.g. Caughley 1994). …”

Section: Discussionmentioning

confidence: 99%

A simple landscape‐scale test of a spatially explicit population model: patch occupancy in fragmented south‐eastern Australian forests

Lindenmayer

McCarthy²,

Possingham³

et al. 2001

Oikos

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The results of a landscape-scale test of ALEX, a widely used metapopulation model for Population Viability Analysis (PVA), are described. ALEX was used to predict patch occupancy by the laughing kookkaburra and the sacred kingfisher in patches of eucalypt forest in south-eastern Australia. These predictions were compared to field surveys to determine the accuracy of the model. Predictions also were compared to a ''naïve'' null model assuming no fragmentation effects. The naïve null model significantly over-predicted the number of eucalypt patches occupied by the sacred kingfisher, but the observed patch occupancy was not significantly different from that predicted using ALEX. ALEX produced a better fit to the field data than the naïve null model for the number of patches occupied by the laughing kookaburra. Nevertheless, ALEX still significantly over-predicted the number of occupied patches, particularly remnants dominated by certain forest typesribbon gum and narrow-leaved peppermint. The predictions remained significantly different from observations, even when the habitat quality of these patches was reduced to zero. Changing the rate of dispersal improved overall predicted patch occupancy, but occupancy rates for the different forest types remained significantly different from the field observations. The lack of congruence between field data and model predictions could have arisen because the laughing kookaburra may move between an array of patches to access spatially separated food and nesting resources in response to fragmentation. Alternatively, inter-specific competition may be heightened in a fragmented habitat. These types of responses to fragmentation are not incorporated as part of traditionally applied metapopulation models. Assessments of predictions from PVA models are rare but important because they can reveal the types of species for which forecasts are accurate and those for which they are not. This can assist the collection of additional empirical data to identify important factors affecting population dynamics.

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“…Thus, the efficiency of dispersal is linked closely to population persistence on these objects. In general, animal populations face two sources of local extinction: an external risk caused by the variability of the environment, and an internal risk based on demographic stochasticity (Caughley, 1994). Among environmental threats, habitat destruction is by far the most serious one.…”

Section: Discussionmentioning

confidence: 99%

Local population persistence as a pre-condition for large-scale dispersal of Idotea metallica (Crustacea, Isopoda) on drifting habitat patches

Gutow

2003

Migrations and Dispersal of Marine Organisms

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Idotea metallica establishes self-sustaining populations exclusively on objects drifting at the sea surface. Largescale transport of drift material with surface currents results in an efficient dispersal of the species. Two types of drifting objects are utilised (biotic and abiotic), providing quite different conditions of life. Ephemeral biotic substrata (mainly uprooted macroalgae) may be used for transport and food, however, resulting habitat destruction from feeding must be a major threat for local population persistence of I. metallica. Abiotic substrata or wood represent efficient vectors for long-distance dispersal due to their resistance to biodegradation, but do not provide food for this herbivorous species. In laboratory experiments, the spatially-limited conditions of drifting substrata were simulated in microcosms. Idotea metallica established persistent populations on both types of substrata. On abiotic substrata, however, where the animals were fed only on Artemia larvae, high variations in density and a reduced intrinsic rate of population growth increased the risk of population extinction. Idotea metallica avoids habitat destruction by limited feeding on macroalgae. In contrast, the coastally distributed congener Idotea baltica destroyed algal habitats by feeding about 10 times faster than I. metallica.

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Directions in Conservation Biology

Cited by 2,019 publications

References 86 publications

Mammal invaders on islands: impact, control and control impact

Mammal invaders on islands: impact, control and control impact

A simple landscape‐scale test of a spatially explicit population model: patch occupancy in fragmented south‐eastern Australian forests

Local population persistence as a pre-condition for large-scale dispersal of Idotea metallica (Crustacea, Isopoda) on drifting habitat patches

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