We collected a total of 304 culpeo faeces. Each scat was air dried, soaked in soapy water, and washed through 1-mm and 3-mm sieves, thus disaggregating the content (hair, feathers, bones, hooves, invertebrate and plant remains) for the identification of prey groups (e.g. Ackerman et al., 1984). Determination of mammalian species was performed according to the patterns of cuticle and medulla in the structure of guard hairs (see Arita and Aranda, 1987; Chehébar and Martín, 1989). Hairs present in the scats were compared with those of a reference collection, which accounted for 46 previously collected potential prey species. Likewise, bone remains were compared when necessary with the reference collection located at San Francisco de Quito University. To estimate biomass consumption by culpeos, the mean body mass for the Ecuadorian species identified as prey was obtained from the literature (e.g. Tirira, 2007), and a maximum consumption of 800 g was assumed considering the culpeo’s size (Sillero-Zubiri et al., 2004). For small food items, such as invertebrates and fruits, representative values of biomass were used (e.g. Malo et al., 2004; see Tab. 1 ).
Food items were classified into eight prey groups (Tab. 1): small mammals, big rodents, armadillos, rabbits, carnivorous (i.e. including marsupial carnivores), cervids, fruits and others (including birds and invertebrates, which were only consumed in small quantities). The relative contribution of each prey item and group to the diet was measured by calculating their frequency of occurrence (FO), i.e. the number of scats in which a given prey item or group was found divided by the total number of scats, expressed as a percentage. Furthermore, the consumed biomass (CB) of each prey group was estimated, and also expressed as a percentage, multiplying the number of each item by its assigned weight and then dividing the result by the total sum of biomass.
Data from the three sampling sites (Fig. 1) were pooled for statistical analyses because sites cannot really be considered as independent areas. Indeed, based on the genetic individualisation of scats, several individuals used more than one site (Authors, unpublished data), so any comparison among sites is rendered meaningless. Then, for the PNP as a whole, G-tests (Sokal and Rohlf, 1981) were performed to search for statistically significant differences in the FO of the eight prey groups in different months. Spearman’s correlation coefficients (Moran, 1948) were calculated to test for the existence of relationships between prey groups over time. The Kruskal-Wallis test was conducted to test for differences in the biomass contribution between prey groups. Moreover, the Shannon-Wiener’s index (Shannon and Weaver, 1949) was used to measure trophic diversity. Data from November and December were combined to get a representative sample size. All statistical analyses were performed using the software Statistica 10 (StatSoft 2011).