Lancaster University

 

 

NERC FUNDED PhD STUDENTSHIP AVAILABLE NOW

(Deadline for applications: February 24th 2008)

 

Survival through the Arctic winter:

How gastrointestinal nematodes influence fitness in Svalbard reindeer

 

 

Supervisors: Dr Ken Wilson; (Lancaster University); Prof Steve Albon and Dr Justin Irvine (The Macaulay Institute); and Dr Steve Coulson (University Centre in Svalbard - UNIS)

Start date: January 2009

 

 

Background and Rationale

Regulation of animal populations by their parasites was demonstrated using mathematical models nearly 30 years ago (Anderson & May 1978, May & Anderson 1978). Theoretical studies examining the dynamics of host-parasite interactions have since flourished (Dobson & Grenfell 1995). However, whilst many empirical studies have quantified the negative impact of parasites on host survival and fecundity (Gulland 1995), few have come close to demonstrating that macroparasites can regulate wildlife populations, mainly due to logistical difficulties (Hudson et al., 2002). There are two exceptions (Wilson 2002): 1) the role of caecal worms (Trichostrongyle tenuis) in red grouse dynamics (Hudson et al 1992, 1998), and 2) the role of abomasal nematode (Ostertagia gruehneri) in Svalbard reindeer dynamics (Albon et al., 2002, Stien et al., 2002).

 

For Svalbard reindeer, quantifying the regulatory role of parasites is possible because a) field experiments are tractable in a long-term individual-based study, b) the system is relatively simple, with no predators or herbivore competitors, and c) there are only two species of parasites: the abomassal dwelling O. gruheneri and Marshallagia marshalli. Interestingly, these two species appear to have evolved different transmission cycles, thereby potentially avoiding competition within the host: while O. gruenhneri seems to be transmitted in the summer, which is typical of gut nematodes, remarkably M. marshalli is transmitted in winter and appears to accumulate in significant numbers between October and March (Irvine et al., 2000). It is therefore likely that these two species have different impacts on the host.

Experiments using anthelmintics that remove O. gruehneri have shown that parasite-mediated reduction in fecundity increases as the intensity of the parasite infection increases, which, in turn is related to the host population density two years earlier (Albon et al. 2002 and featured in Begon, Townsend & Harper 2006 Ecology: From Individuals to Ecosystems, 373-376). Recent developments in anti-parasite drug delivery now permit an experimental manipulation of the impact of the winter-transmitted M. marshalli on the reindeer hosts. M. marshalli, is an ostertagid like parasite of animals in cold deserts and can have negative impacts on its hosts (Morgan et al., 2004).

This studentship will test the hypothesis that, since M. marshalli infects reindeer over winter when they are starving, it depresses host performance, reduces survival and has a role in regulating reindeer population dynamics.


 

Methodology and Approach

Study area and animals: Located on Nordenskiold, Spitsbergen, Svalbard (78 N, 15 E), individual, marked reindeer have been followed since 1994, providing measures of growth, fecundity and year of death. Each April, up to 150 individuals are re-captured using a net from snow scooters.

Experimental Design: When reindeer are captured, anti-helminth drugs can be administered to remove their parasite burden at specific times of year. This will allow us to test a number of specific predictions about the interaction between the reindeer and its parasites:

 

1)   After 4 months (in February), reindeer treated with the delayed-release bolus will have a lower abundance of parasites than untreated controls, and these parasites will be largely M. marshalli.

 

2)   By April, the proportional decline in body weight and body fat will be lower in the treatment groups than in the untreated controls, with those receiving a second dosing in February losing least condition.

 

 

3)   Differences in relative change in body condition between treated animals and untreated controls will increase with winter severity (total precipitation Oct-Apr) and host density.

 

4)   The probability of survival to the following winter will be highest in treated animals, especially those receiving a second dosing.

 

Research training

The student will receive an induction into theoretical population ecology, and specifically host-parasite interactions, through Lancaster University.

The CASE partner (Macaulay Institute) will provide practical training in animal capture-mark-recapture, field experimentation and monitoring, as well as advanced statistics facilitated by Biomathematics and Statistics Scotland.

The student will learn basic parasitological laboratory methods, as well as molecular techniques at the University of Aberdeen, to distinguish both larval and adult stages of the nematode species (Dallas et al. 2000; Irvine & Dallas., 2002).

The student will take part in field studies on Svalbard during several weeks each year, where they will be associated with the University Centre in Svalbard (UNIS).

 



 

Application procedure

Informal enquiries can be made to Dr Ken Wilson (email: ken.wilson@lancaster.ac.uk) or Prof Steve Albon (s.albon@macaulay.ac.uk).

You mat apply online at https://www.pgapps.lancs.ac.uk/

University application forms and guidance notes are available online at:

http://www.lancs.ac.uk/users/admissions/postgrad/pgform1.htm

Email enquiries to: lec.pg@lancaster.ac.uk

Additional information about PhDs within the Lancaster Environment Centre can be found at: http://www.lec.lancs.ac.uk/postgraduate/phd/

Interviews will be held between 10th and 14th March 2008


 

References

Albon, S. D., Stien, A., Irvine, R.J., Langvatn, R., Ropstad, E. & Halvorsen, O. (2002). The role of parasites in the regulation of a reindeer population. Proc. Royal Society B. 269, 1625-1632.

Anderson R.M. & May R.M. (1978). Regulation and stability of host-parasite population interactions. I. Regulatory processes. J. Anim. Ecol. 47, 219-247.

Dallas, J.F., Irvine, R.J. Halvorsen, O. & Albon, S.D. (2000). Identification by polymerase chain reaction (PCA) of Marshallagia marshalli and Ostertagia ostertagi in Svalbard reindeer. Int. J. Parasitology, 30, 863-866.

Dobson, A. P. & Grenfell, B. T. (1995). Introduction. pp. 1-19. In Ecology of Infectious Diseases in Natural Populations (ed. Grenfell, B. T. & Dobson, A. P.), Cambridge University Press, Cambridge.

Gulland, F.M.D. (1995). The impact of infectious diseases on wild animal populations ‑ a review. pp 20‑51 in Ecology of Infectious Diseases in Natural Populations (ed B.T. Grenfell & A.P. Dobson) Cambridge University Press.

Hudson, P.J., Newborn, D. & Dobson, A.P. (1992). Regulation and stability of free-living host-parasite system: Trichostrongylus tenuis in red grouse. I. Monitoring and parasite reduction experiments. J. Anim. Ecol. 61, 477-486.

Hudson P.J., Dobson, A.P. & Newborn, D (1998). Prevention of population cycles by parasite removal. Science, 282, 2256-2258.

Hudson, et al (2002). The Ecology of Wildlife Diseases, Oxford University Press, Oxford.

Irvine, R.J., Stien, A., Halvorsen, O., Langvatn, R. & Albon, S.D. (2000). Life-hisory strategies and population dynamics of abomasal nematodes in Svalbard reindeer (Rangifer tarandus platyrhynchus). Parasitology 120, 297-311.

Irvine, R. J., & Dallas, J. F. (2002). Efficient Polymerase Chain Reaction (PCR) detection of the Internal Transcribed Spacer (ITS2) of mucosa derived larvae is dependent on the larval extraction method. J.Parasitology, 88, 807-809.

May R.M. & Anderson R.M. (1978). Regulation and stability of host-parasite population interactions. II. Destabilising processes. J. Anim. Ecol. 47, 249-267.

Morgan, E. R., Milner-Gulland, E. J., Torgerson, P. R. & Medley, G. F. (2004). Ruminating on complexity: macroparasites of wildlife and livestock. TREE 19, 181-188.

Stien, A., Irvine, R.J., Ropstad, E., Halvorsen, O., Langvatn, R. & Albon, S. D. (2002). The impact of gastrointestinal nematodes on wild reindeer: experimental and cross - sectional studies. J. Anim. Ecol. 71, 937-945.

Wilson, K. (2002). Ups and downs of wildlife population regulation by macroparasites. TREE, 17, 454.


 

 

(all photographs copyright Erik Ropstad)