Population crash in an invasive species following the recovery of a native predator: the case of the American grey squirrel and the European pine marten in Ireland

Sheehy, Emma; Lawton, Colin

doi:10.1007/s10531-014-0632-7

Cited by 56 publications

(70 citation statements)

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“…Dispersing squirrels may be more difficult to detect with baited equipment because they are transient rather than exploring or foraging and do not remain in the area to become familiar with experimental devices. A recent hair-tube study in an Irish woodland with an established grey squirrel population recorded 20% of hair tubes positive for grey squirrel (Sheehy and Lawton 2014), which is considerably higher than any proportion of grey squirrel-positive tubes found in the current study. Squirrels in low-density populations may also be less likely to interact with baited equipment because of incomplete exploitation of natural food resources.…”

Section: à2contrasting

confidence: 80%

Locating species range frontiers: a cost and efficiency comparison of citizen science and hair-tube survey methods for use in tracking an invasive squirrel

et al. 2014

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Context. Improved knowledge of changing species distributions is critically important for conservation managers in the face of increasing species invasions, habitat disturbance and climate change. Efficient monitoring of the location of advancing species invasion frontiers is especially crucial for effective species community and habitat management.Aims. To compare the cost-effectiveness and efficiency of two survey methods, a citizen science survey and a traditional hair-tube survey, in their abilities to locate the current southern invasion frontier of grey squirrels (Sciurus carolinensis) in Ireland.Methods. In the citizen science survey, we collected sighting reports of the grey squirrel and its native congener, the red squirrel (S. vulgaris), from the geographic region of the invasion frontier from untrained members of the public over a 2-year period. Hair-tube surveys were carried out in 14 woodlands (!30 ha) in the same geographic area to test the ability of this indirect field method to identify colonising grey squirrel populations. The costs, efficiency and cost-effectiveness of each method were compared.Key results. The citizen science sighting reports resulted in the clear delineation of the southern frontier of the zone invaded by the grey squirrel. The hair-tube survey ascertained the presence of grey squirrels in 4 of 14 sites, but did not detect this species close to the invasion frontier defined by the citizen science survey. Even though the total cost of the citizen science survey was higher, it was more cost-effective and efficient on a per detection basis for the purposes of detecting the presence of grey and red squirrels.Conclusions. The citizen science survey detected invasive squirrels in sites where the hair-tube survey did not. As such, the citizen science survey provided a more comprehensive snapshot of the location of the grey squirrel invasion frontier more efficiently and cost-effectively than did traditional field techniques.Implications. In the face of increasing ecological and economic costs of biological invasions, we recommend straightforward citizen science surveys, over indirect field surveys, to managers and researchers seeking to efficiently track progressing invasions of readily observable animals cost-effectively.

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Section: à2contrasting

confidence: 80%

Locating species range frontiers: a cost and efficiency comparison of citizen science and hair-tube survey methods for use in tracking an invasive squirrel

et al. 2014

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“…Our results complement the observations of landscape-scale negative correlations between grey squirrel abundance and pine marten presence (Sheehy & Lawton, 2014;Sheehy et al, 2018).…”

Section: Discussionsupporting

confidence: 85%

Translocated native pine martens Martes martes alter short‐term space use by invasive non‐native grey squirrels Sciurus carolinensis

McNicol

Bavin

Bearhop

et al. 2020

Journal of Applied Ecology

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1. Predators can shape the distributions and dynamics of their prey through direct and indirect mechanisms. Where prey animals are regarded as pests, the augmentation of predator populations might offer a potential tool in their management. Declines in invasive non-native grey squirrel Sciurus carolinensis populations inIreland and Scotland have been related to an increase in range and density of native pine marten Martes martes populations. These reductions in grey squirrel abundance have, in turn, been linked to recovery of native red squirrels Sciurus vulgaris. Taking the opportunity presented by a conservation translocation of pine martensfrom Scotland to Wales, we investigated the short-term effects of exposure to translocated martens on the space use and survival of resident grey squirrels. 4. Grey squirrel range size and daily distance travelled increased significantly with increasing exposure to martens but we found no effect of marten exposure on the recapture probability (i.e. apparent survival) of the sampled squirrels within the study time frame. This is suggestive of contemporary, non-lethal effects changing the ranging or foraging regimes of squirrels, due either to predator avoidance and/ or earlier lethal effects associated with a reduction in intraspecific competition. Synthesis and applications.Our evaluation mimics the conditions experienced by grey squirrels at the front edge of naturally recovering pine marten populations and presents direct evidence that pine marten translocations could play an influential role in the behaviour and dynamics of invasive non-native grey squirrel populations. Translocations of native predators, undertaken primarily for biodiversity conservation, could therefore find additional application in managing the ecological and economic impacts of invasive non-native prey. K E Y W O R D S biological control, grey squirrel, home range, invasive species, landscape of fear, pine marten, reintroduction, translocation | 905 Journal of Applied Ecology McNIcOL et aL.

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“…Simberloff and Gibbons (2004) found little directed research investigating collapse of non-native species populations and concluded that this phenomenon is of little importance to invasion biology. However, since 2004 additional examples of population collapse have been observed in non-native taxa as diverse as ants (Cooling et al 2012), crayfish (Sandstrom et al 2014), and mammals (Sheehy and Lawton 2014). Few additional fish examples have been published but spontaneous collapse for unknown reasons has been noted for the widespread, invasive topmouth gudgeon (Pseudorasbora parva Temminck and Schlegel) in Europe (Copp et al 2007).…”

Section: Discussionmentioning

confidence: 99%

“…Few additional fish examples have been published but spontaneous collapse for unknown reasons has been noted for the widespread, invasive topmouth gudgeon (Pseudorasbora parva Temminck and Schlegel) in Europe (Copp et al 2007). Predation by native species is seldom thought to be the cause of these newer examples (but see Sheehy and Lawton 2014). Boom-and-bust cycles and spontaneous population collapse for non-native fishes in Florida are mentioned in the literature but accounts are largely anecdotal (but see Harrison et al 2013 andBoucek and for cold effects).…”

Section: Discussionmentioning

confidence: 99%

Collapse of a reproducing population of non-native African jewelfish (Hemichromis letourneuxi) in a Florida lake

Hill¹

2016

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Established populations of non-natives may collapse without a clear causal mechanism. Hypothetically, fluctuations in habitat structural complexity may influence dynamics of invaders and the biotic resistance offered by predators. Herein I report observations of the collapse of a reproducing population of the nonnative African jewelfish (Hemichromis letourneuxi) in a Florida lake concurrent with an unusual low-water period. I test the hypothesis that predation may have played a key role in the collapse using a combination of field surveys of habitat and fish abundance and predator-prey experiments. Habitat complexity was high before and after the low water period but virtually nonexistent during low water. The abundance of African jewelfish and native juvenile bluegill (Lepomis macrochirus) and eastern mosquitofish (Gambusia holbrooki) declined concurrently with decreasing complexity but the native species rebounded when lake levels increased. Large-bodied natives such as largemouth bass (Micropterus salmoides) and adult bluegill showed no pattern of fluctuation related to habitat complexity. African jewelfish survival was 1.6 times greater at high versus low complexity and over 7 times higher versus no complexity in the presence of largemouth bass. Conversely, eastern mosquitofish, a species that exerts strong effects on small-bodied fishes in structurally complex habitats had no effect on African jewelfish survival. Predation effects on susceptible non-natives should be considered as a potential control action. Population collapse is understudied but may provide insights into long-term dynamics of invaders and information useful for management of problematic species.

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Population crash in an invasive species following the recovery of a native predator: the case of the American grey squirrel and the European pine marten in Ireland

Cited by 56 publications

References 36 publications

Locating species range frontiers: a cost and efficiency comparison of citizen science and hair-tube survey methods for use in tracking an invasive squirrel

Locating species range frontiers: a cost and efficiency comparison of citizen science and hair-tube survey methods for use in tracking an invasive squirrel

Translocated native pine martens Martes martes alter short‐term space use by invasive non‐native grey squirrels Sciurus carolinensis

Collapse of a reproducing population of non-native African jewelfish (Hemichromis letourneuxi) in a Florida lake

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