Temporal host-parasite relationships of the wild rabbit, Oryctolagus cuniculus (L.) as revealed by stable isotope analyses

INTRODUCTION

The European rabbit (Oryctolagus cuniculus ) was most likely introduced into the United Kingdom in the late twelfth century (Lever, 1977). Due to its rapid reproductive cycle and changes in land management (Pollard, Hooper & Moore, 1974), the European rabbit is now one of the major agricultural pests with an estimated loss of revenue of >£100 million to UK agriculture (Mills, 1986). Consequently, the ecology of the rabbit has been well studied (Thompson & King, 1994). However, there is a paucity of data on both the temporal trophic dynamics of the rabbit and the trophic-level interactions between the rabbit host and its parasites.

Naturally occurring stable isotopes of carbon (C) and nitrogen (N) have been utilized by ecologists and zoologists as a tool to determine trophic relationships within a community (e.g. Tieszen et al . 1979; Hobson & Welch, 1992; Scrimgeour et al . 1995; Neilson et al . 1998; Neilson, Boag & Smith, 2000). Furthermore, hitherto unknown temporal changes in diet have also been identified using stable isotope analyses (Ramsay & Hobson, 1991; Ben-David, Flynn & Schell, 1997; Godley et al . 1998; Hobson, Drever & Kaiser, 1999). Natural abundances of stable isotopes are effectively an integrated record of assimilated elements such as C and N (Peterson & Fry, 1987; Robinson, 2001) and, as such, are a better representation of the recent biochemical and dietary past of an organism than traditional snapshot methods, e.g. gut content analyses. Changes in the ratios of ¹³ C/¹² C and ¹⁵ N/¹⁴ N (expressed as Δ¹³ C and Δ¹⁵ N) in animal tissue are indicative of dietary sources and trophic grouping, respectively (DeNiro & Epstein, 1978, 1981; Wada, Kabaya & Kurihara, 1993). Animal tissues such as muscle, hair (fur) and liver have different turnover rates of carbon and nitrogen due to differences in their metabolic activity (Tieszen et al . 1983; Hobson & Clark, 1992; Pinnegar & Polunin, 1999) and have been used as a proxy to indicate short and long-term dietary sources in birds (Hobson & Sealy, 1991; Hobson & Clark, 1992; Hobson, 1993), mammals and reptiles (Tieszen et al . 1983; Ames, van Vleet & Sackett, 1996; Hilderbrand et al . 1996; Godley et al . 1998; Hobson et al