Long term surveillance reveals nematode Elaphostrongylus cervi as a practical indicator of red deer management

Abstract Measures of performance in wild ungulates must consider density dependent and stochastic factors such as parasitic rates (as natural enemies in intimae relation with hosts) along with the impact of population management. In order to standardize parasite counts to be useful ecological indicators, it is essential to test host and parasite responses to the abovementioned. In the Iberian Peninsula, the parasitic nematode Elaphostrongylus cervi and its host the red deer (Cervus elaphus) provide an excellent practical scenario to illustrate how parasitic rates should be interpreted under different management contexts. Our study focuses on two distinct management scenarios, one deer population (LM) with supplemental feeding and one population (QM) with almost no human intervention, aside from hunting. We aim to assess how management (supplemental feeding) modulates the relationships of density dependent, stochastic and individual factors, and E. cervi faecal larvae counts in the red deer, so as with other physiological traits (body condition and spleen weight - as a proxy to immunological status). Overall, we have shown the decisive role that density and precipitation can have in a Mediterranean environment, with different trends in the two studied areas (e.g. negative correlation between E. cervi and red deer density in supplemented population, in opposition to un-supplemented). The crucial role that precipitation combined with density can have on deer dynamics, along with the artificial feeding as buffer of some traits, reinforces the need for an adaptive management, and the demand to manage each population considering the surrounding environment. Management strategies selected in each site can establish populations dynamics and health and should be closely monitored in a long-term context, as it occurs in our study.