Dr Sarah Burthe

Animal Population Ecologist

Current work

I am an Animal Population Ecologist, working with the Isle of May seabird group. I work on two main projects: SPACE (Shifting Phenology: Attributing Change across Ecosystems) and IMLOTS (Isle of May Long-Term Study).

I am investigating whether changes in phenology (timing of breeding) are affecting animal population dynamics. Although phenology changes associated with climate warming have been widely documented, the majority of work has focused on terrestrial ecosystems. We are investigating rates and directions of phenological change across a wide variety of taxa from three ecosystems (marine, freshwater and terrestrial) using extensive long-term data from the UK. This is the first standardised and unbiased analysis of phenology across ecosystems and will greatly facilitate our understanding of the impacts of climate change.

Using the Isle of May system as a case-study, I am examining evidence for trophic-mismatch between seabirds and their sandeel prey. Trophic mismatch occurs when predators do not sufficiently adjust the timing of breeding to match the phenology, and hence availability, of their prey. I am investigating whether there is increasing asynchrony over time between sandeel phenology and seabird phenology, and whether this mismatch is having an impact on seabird fitness (survival and reproductive success), or whether other drivers are more important.

I am also investigating whether population-level phenology change in shags is caused or masked by changes in the age-structure of the population. Younger birds tend to breed later in the season than older birds, and preliminary analysis suggests that the age of recruitment varies between years.

With Liverpool University, I am currently evaluating whether pathogen infection delays the onset of maturity of field voles, utilising program E-SURGE, a newly developed capture-mark-recapture statistical program capable of examining changes in host states.

Research interests

I am primarily interested in understanding the drivers of changes in animal population dynamics, via effects on survival and reproduction, with a particular interest in disease and parasite ecology.

I am keen to expand my work investigating the impact of infections in natural populations, to the seabird system on the Isle of May. Seabirds are well-suited for disease and parasite studies because: uniquely marked individuals can be sampled repeatedly though time; much is already known about their population dynamics and demographic rates over a long time period, experimental manipulations can be undertaken easily, and because reproductive parameters can be directly observed in order to quantify fitness effects.

Seabird population declines in the North Sea have generally been attributed to reduced prey availability. However, there is much interspecific and regional variation in population trends suggesting that the situation is complex and other factors may be involved. One potentially important seabird population driver that has largely been ignored is disease, with very few studies have evaluated the impact of endemic pathogens and parasites on seabird host fitness in the wild.

Most studies that have investigated the impacts of parasites on wildlife hosts have only considered single-parasites, despite the fact that hosts are frequently simultaneously infected with a wide range of macro- and micro-parasites. I am hoping to identify concomitant infections in seabirds, and to evaluate experimentally whether multiple infections are having additive or multiplicative effects on host fitness.

Brief CV

• April 2008 to present: Animal Population Ecologist at CEH at Edinburgh.
• June 2007 to April 2008: PDRA at Liverpool University investigating the impact of multi-pathogen infections on wild rodent hosts.
• 2006: Newcastle University. PDRA investigating squirrel poxvirus infection in wild grey squirrel populations. . Supervised by Dr S. Rushton and Prof. J. Gurnell.
• 2001-2005: University of Liverpool. PhD thesis title: The role of endemic pathogens, vole tuberculosis (Mycobacterium microti) and cowpox virus, in the cyclic population dynamics of field voles (Microtus agrestis). Supervisors: Prof . M. Begon, Prof. M. Bennett & Prof. X. Lambin. I studied the impact of two endemic diseases (cowpox virus and vole tuberculosis Mycobacterium microti) on the population dynamics of wild field vole hosts in Kielder Forest, UK. I found that voles infected with cowpox virushad a significantly lower probability of surviving than uninfected voles, both at the individual level and the population level, thus disputing thelong-standing view of population ecologists that endemic diseases do not impact on population dynamics. Vole tuberculosis prevalence was investigated over a wide spatial area, providing the first detailed investigation into the pathology and prevalence of this disease in UK wildlife.
• 1996-2000: BSc Honours Zoology (1st Class), University of Aberdeen.

Selected publications

Smith, M. Telfer S., Kallio, E., Burthe, S. et al. 2009. Host-pathogen time series data in wildlife support a transmission function between density and frequency dependence. PNAS 106: 7905-7909.

Begon M., Telfer S., Smith M.J., Burthe S.J., Paterson, S. & Lambin X. (2009) Seasonal host dynamics drive the timing of recurrent epidemics in a wildlife population. Proc. Roy. Soc. 276: 1603-1610.

Burthe, S.J. et al. 2008. Cowpox virus infection in natural field vole, Microtus agrestis, populations: significant negative impacts on survival. J. An. Ecol. 77: 110-119.

Burthe, S.J. et al. 2008 Tuberculosis (Mycobacterium microti) in wild field vole populations. Parasitology 135: 309-317.

Burthe, S.J. et al. 2006 Cowpox virus infection in natural field vole Microtus agrestis populations: delayed density dependence and individual risk. J. An. Ecol. 75: 1416-1425.

Telfer, S., Begon, M., Bennett, M., Bown, K.J., Burthe, S.J., et al. 2006. Contrasting Dynamics of Bartonella spp. in Cyclic Field Vole populations: the Impact of Vector and Host Dynamics. Parasitology 134: 413-425.

Bambini, L. Blyth, A., Bradford, T., Burthe, S, et al. 2006. Another Seychelles endemic close to extinction: the emballonurid bat Coleura seychellensis. Oryx 40:310-318.

Bown, K.J., Begon, M., Bennett, M., Birtles, R., Burthe, S.J., Lambin, X., Telfer, S., Woldehiwet, Z. & Ogden, N.H. 2005 Sympatric Ixodes trianguliceps and Ixodes ricinus ticks feeding on field voles (Microtus agrestis): potential for increased risk of tick-borne zoonotic infections in the United Kingdom. Emerg. Infect. Dis. In Press.

Smith, A., Telfer, S., Burthe, S.J., Bennett, M. & Begon, M. 2005 Trypanosomes, fleas and field voles: ecological dynamics of a host-vector-parasite interaction. Parasitology 131:355-365.