Modelled rat and stoat population responses to mast-seeding events

  • Image, rats and stoats mast seeding events.

    Mast-seeding events occur when plant species (eg New Zealand flax or beech trees) produce very large amounts of seed, usually every 4–6 years. These events are vital for the survival of some indigenous bird species. Unfortunately, the increase in food supply also prompts a dramatic increase in the numbers of mice, rats, and stoats (a population irruption). In the years after mast-seeding events, rats and stoats target birds and other prey.

    We classified Modelled rat and stoat population responses to mast-seeding events as supporting information.

    Key findings

    After a mast-seeding event, rat and stoat populations can increase to up to five to nine times their normal peak numbers, respectively.

    • The number of rats is estimated to increase from a normal peak of 190/100ha to 860/100ha after a mast-seeding event.
    • The number of stoats is estimated to increase from a normal peak of 2/100ha to 17/100ha after a mast-seeding event.
    • From their peak, rat numbers take approximately seven months to decrease to their baseline levels.
    • Stoat numbers decrease much slower than rat numbers, taking approximately 17 months to return to baseline levels.

    Figure 1

    land-pests-rats

    Note: The bar shows the period when seeds from the mast event fall in large numbers.

    Figure 2

    Graph, Modelled population responses of stoats to mast-seeding events.

    Note: The bar shows the period when seeds from the mast event fall in large numbers.

    Definition and methodology

    Population models for rat and stoat responses were derived from empirical studies.

    See Rodent and predator population dynamics in an eruptive system (Blackwell et al, 2001) for details on the modelling methods used.

    Data quality

    We classified Modelled rat and stoat population responses to mast-seeding events as supporting information.

    Relevance

    relevance-partial This supporting information is a partial measure of ‘Pests, diseases, and exotic species’ topic.

    Accuracy

    accuracy-medium The accuracy of the data source is of medium quality.

    See Data quality information for more detail.

    References

    Blackwell, GL, Potter, MA, & Minot, EO (2001). Rodent and predator population dynamics in an eruptive systemEcological Modelling, 25, 227–245.

     

    Published 21 October 2015

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