Study areanext section
The study was conducted in the high areas of the Podocarpus National Park (PNP), this being the most important protected area in southern Ecuador (Fig. 1). It is located within the so-called ‘Huancabamba depression’, which is considered a transition zone between the Northern and Southern Andes mountains because their maximum elevations (3800 m.a.s.l) are the lowest in the Andean range. The PNP occupies 145000 ha of this region, in the provinces of Loja and Zamora-Chinchipe (MAE, 2015). The PNP has a humid-subhumid ombrotype and the temperature varies between 2 and 22 °C. The vegetation consists of tropical rainforest at low altitude, followed by different types of Sub-Andean, Andean and High-Andean forest (i.e. cloud forests) at higher altitudes. Between 2600 (m.a.s.l) and the high peaks (3600 m.a.s.l.) a moorland type habitat (known as ‘paramo’) appears, occupying a narrow strip along the ridge in a north-south gradient (Rivera, 2007; MAE, 2015). These paramos are characterised by the abundance of rosette and pad plant species: Bambu and Chusquea are the dominant plant genus, alongside Polylepis, Escallonia and Clusia shrub species (see Sierra, 1999). These mountain ecosystems in the PNP are the most humid in Ecuador, with rainfall exceeding 6000 mm/year, low temperatures and strong winds (Richter, 2003; Rivera, 2007).
Collection of culpeo scats
This study is based on analysing scat contents to determine the culpeo’s diet. It is a non-invasive method that shows what the species real consumes (Putman, 1984; Corbett, 1989) and is widely used for studying the feeding habits of carnivores (e.g. Halter, 1967; Reynolds and Aebischer, 1991; Juarez and Marinho-Filho, 2002; Malo et al., 2004). In Particular, this method has already been used to study the culpeo’s diet (e.g. Iriarte et al., 1989; Ebensperger et al., 1991). All accessible areas of paramo in the PNP were sampled for culpeo scat collection. These areas were concentrated in three zones of the PNP known locally as Cajanuma, El Tiro and Cerro Toledo. A different number of fixed 1-km transects (16 in total) were established in each area on existing paths (see Fig. 1). During 2009 each 1-km transect was sampled in search of fresh scats once a month (thus resulting in a total of 192 km of overall sampling effort), at 30 day intervals and starting in the middle of each month (so that any scat found was assigned to the corresponding sampled month). Previously, a survey to remove old scats was undertaken in all transects. Samplings were always conducted by the same observers, who were well trained prior to starting the fieldwork (Lozano et al., 2013).
Collected scats were stored at -80 °C when clearly identified as belonging to Andean foxes. Scats were first identified based on a set of context-based diagnostic characteristics (Romo, 1995; Cornejo and Jiménez, 2001; Achilles, 2007; Palacios et al., 2012; Pia, 2013), which included location (scats directly on the path or close by), general morphology (canid-like scats, different from those of cats, bears, etc), and diameter (2-3 cm). In addition, genetic analyses were performed in the lab to confirm scat identification. 89 scats were randomly selected from the total sample, and DNA was extracted by applying the QIAGEN QIAamp DNA Stool Mini Kit (QIAGEN, CA.USA). The protocol described by De Barba et al., (2014) was used for mitochondrial DNA amplification. Amplification was successful for 81.2% of the total sample (i.e. 70 scats), the genetic material being positively identified as belonging to culpeo in all cases. Therefore, observers in the field had a 100% success rate in the identification of these 70 scats, demonstrating that with good previous training correct identification of culpeo scats based on external features is possible in the area (see Lozano et al., 2013). Hence, no relevant confusion with the scats of other animals inhabiting the same environment, such as pumas (Puma concolor), Andean bears (Tremarctos ornatus) or domestic dogs (Canis familiaris), was assumed.
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).