Abstract/Summary

Climate change is expected to expand the geographic ranges of ectoparasites, increasing the transmission of vector-borne diseases and thereby necessitating a better understanding of ectoparasite-host trophic dynamics. Haematophagous ectoparasites can serve as valuable subsamples of their hosts, retaining isotopic values that reflect dietary information in both their blood meals and tissues. However, the differences in the lifestyles and feeding strategies of lice, fleas, and ticks may influence how these isotopic values are preserved. Here, stable isotope values of carbon (δ13C) and nitrogen (δ15N) were used to investigate trophic interactions between ectoparasites and their mammalian hosts in three pairings: lice (Anoplura: Polyplacidae; n = 101) and Eurasian red squirrels Sciurus vulgaris, fleas (Siphonaptera: Ceratophyllidae; n = 92) and fat dormice Glis glis, and ticks (Ixodida: Ixodidae; n = 16) and European hedgehogs Erinaceus europaeus. Our findings indicate ectoparasites reflect the dietary patterns of their host, with lice exhibiting the closest isotopic values, followed by fleas and ticks. All ectoparasites had significantly higher nitrogen isotope values compared to those of their hosts, indicative of trophic enrichment, but their carbon isotope values varied. Notably, we found that the presence of a blood meal did not significantly affect the isotopic values found in lice and fleas, while ticks showed a significant difference between exoskeleton and blood meal in δ13C values. This study highlights the importance of understanding how the life histories of parasite species influence the preservation of isotopic host signals in order to be able to utilise stable isotope analyses of ectoparasites (particularly lice) to infer host dietary niches and preferences, with broader implications for understanding host-parasite dynamics and predicting disease transmission pathways.