European red squirrel population dynamics driven by squirrelpox at a gray squirrel invasion interface.

Area of Science:

• Ecology
• Conservation Biology
• Veterinary Science

Background:

• Non-native species introductions can facilitate native population declines via infectious diseases.
• Squirrelpox virus (SQPV) is suspected in the decline of UK red squirrels (Sciurus vulgaris) post-gray squirrel (Sciurus carolinensis) introduction.
• Understanding this dynamic is crucial for red squirrel conservation and managing invasive species.

Purpose of the Study:

• To analyze time series data on squirrel abundance and squirrelpox disease (SQPx) incidence in Merseyside.
• To determine the impact of SQPV and non-native gray squirrels on native red squirrel populations.
• To identify the drivers of SQPx outbreaks in red squirrels.

Main Methods:

• Analysis of time series data on red squirrel and gray squirrel abundance.
• Assessment of squirrelpox disease (SQPx) incidence in red squirrels.
• Retrospective serological analysis to determine red squirrel survival rates post-SQPV exposure.

Main Results:

• SQPx significantly negatively impacts red squirrel densities and population growth rate (PGR).
• Gray squirrel presence, not density, influenced red squirrel density but not PGR.
• SQPx outbreaks in red squirrels are linked to previous red squirrel infections and local gray squirrel infections, suggesting gray squirrels initiate outbreaks.

Conclusions:

• The UK red squirrel-gray squirrel system exemplifies native species decline facilitated by introduced infectious diseases.
• SQPV-infected gray squirrels are potential initiators of SQPx epidemics in red squirrels.
• Disease prevention and control are paramount for red squirrel conservation efforts in the UK.