Mesopredator abundances, prey interactions and diet of Caracal caracal and Canis mesomelas in the Gamkaberg, Western Cape

[摘要] ENGLISH ABSTRACT: Carnivore conservation is considered a priority due to a rise in conflict between involved species and humans. Conservation strategies are thus essential in ensuring the persistence of carnivores in carnivore-human conflict. This conflict affects many livestock farmers, whose main concern is the loss of income due to livestock deaths from predators. Reported incidences of depredations could intensify the human-wildlife conflict in an area, which could potentially result in predators being killed by, for example, trapping and through sport hunting. This measure-for-measure retaliatory response can drive predators to local and regional extirpation, often resulting in an increase of wild herbivore densities. Small stock farmers in South Africa regard leopard, caracal (Caracal caracal) and black-backed jackal (Canis mesomelas) as vermin. In the Gamkaberg region of South Africa's Western Cape Province, the diet of the Cape leopard has been studied quite extensively, but research on the diets of the black-backed jackal and the caracal in the area is lacking. Consequently, this study focussed on the distribution and diet of caracal and black-backed jackal using camera traps and scat and stomach content analyses.The first part of this thesis focuses on the diets of the two species and compares dietary preferences on farmland and in conservation areas. Results pose a clear contrast to livestock farmers' view on these predators' natural diet. Both focal species were found to prey upon predominately smaller prey and were opportunistic. Insects were found in approximately 10% of both the jackal and caracal scats. Other invertebrates were also identified in the scats of both species, including scorpions and Solifugae. The stomachs of 11 black-backed jackal contained Solifugae and egg remnants; the softer nature of such diets makes it difficult to detect them in scats. Stomach content analyses thus indicated more recent and detailed diet results, in particular for the opportunistic black-backed jackal that ingests many soft-tissue prey items, such as carrion and Arthropoda that rarely persist through the digestive tract. Mammals, especially rodents, are a very important food source for mesopredators and were found in most of the samples for both jackal and caracal. In this study, 83.3% and 88.1% of jackal and caracal scat samples, respectively, contained rodent parts. Rodents, therefore, account for a significant part of both mesopredators' diets in the Little Karoo. The large variation found in both the caracal and black-backed jackal diets confirmed their opportunistic feeding nature in the Gamkaberg. This flexibility in diet, especially for the black-backed jackal, makes it difficult to determine a prey-specific preference pattern. The diets of the focal species in this study are adaptable to time, space and prey availability.The second part of the thesis focuses on estimating population density based on camera trapping. Population size and density estimates are informative to conservation and management planning but are difficult to estimate, especially if the species is rare or elusive. This study used estimators based on relative abundance and presence-absence records to assess the relative abundance of caracal and black-backed jackal in the study area. Camera traps were used for a 10 month period(June 2014-April 2015) in farmlands and conservation areas, whilst also testing different samplingefforts. Graphs were produced to illustrate activity periods of the focal species throughout the year.In particular, caracal and black-backed jackal were found to roam in overlapping areas, preying onsimilar species and showing similar activity patterns. A significant difference was found betweenprey diversity of the two land-uses (P=0.001). Significant differences were also found betweenrandomised and intensive sampling (P=0.03) as well as between randomised and extensivesampling (P=0.05). However, there were no significant differences in prey diversity betweenintensive and extensive sampling. In total, 28 caracal and 115 black-backed jackal occurrenceswere recorded on camera traps, with less caracal and black-backed jackal detected on farmlandsthan in conservation areas, indicating their preference for natural prey in reserves over prey onfarmlands. This also corroborates the results from the scat samples found on farmlands and inconservation areas for both focal species.

[发布机构] Stellenbosch University