Convergence and divergence in prey of sympatric canids and felids: opportunism or phylogenetic constraint?

Abstract

Since the canids and felids diverged in the mid-Eocene or earlier, each family has developed a suite of morphological and behavioural adaptations for obtaining and consuming prey. We here distinguish between prey taxa captured and eaten as a result of these phylogenetic adaptations, and those because they are fortuitously encountered, and argue that such supplementary prey, often opportunistically caught, create a buffer between sympatric, and potentially competitive, canids and felids and thus enhance coexistence. We base our analysis on dietary data derived from the stomach contents of four sympatric canid and felid species in the Free State Province, South Africa (canids: Cape fox Vulpes chama and black-backed jackal Canis mesomelas ; felids: African wild cat Felis silvestris lybica and caracal Caracal caracal ), and from results of studies on these species elsewhere in southern Africa. The two canid species preyed heavily on invertebrates, and thus opportunistically, while the felids (especially the caracal) concentrated on mammals, prey they are phylogenetically adapted to capture. Only three species of mammalian prey are shared by the four species. The ratio of opportunistically-to-phylogenetically mediated prey taxa used (the O/P ratio) differ between the species, with the black-backed jackal having the most opportunistically caught taxa in its diet, and the caracal the least. As predicted, a comparison of this data with those from dietary studies of the same species carried out elsewhere indicates that the number of opportunistically obtained prey taxa varies more than those resulting from phylogenetic adaptations. The largest canid had the widest food spectrum (35 prey taxa) while the smallest felid had the most restricted one (11 prey taxa). We argue that using the O/P distinction allows a better understanding of changes in food niche breadth of particular species, especially in xeric areas, and gives a better indication of possible exploitative competition for food by sympatric carnivores than when regarding all prey taxa as actively pursued.

Polar Bear Diets and Arctic Marine Food Webs: Insights From Fatty Acid Analysis

“…Previous anecdotal reports of predation on other marine mammals have provided an indication of the broader foraging patterns quantified in this study. Polar bears appear to be capable of opportunistically altering their foraging tactics (Kok and Nel 2004) to take advantage of locally abundant food resources (e.g., harp seals in the whelping patch off Newfoundland) as well as effectively hunting largebodied and energy-rich prey (e.g., walruses, beluga whales). These findings suggest that at least some polar bears may be able to cope with a fluctuating arctic environment by adapting their foraging habits to suit local conditions.…”

The bat-eared fox: A dietary specialist?

“…For statistical analyses, prey items were grouped using taxonomic-ecological categories (Jędrzejewska and Jędrzejewski 1998;Kok and Nel 2004): (I) Northern harvester termites (Hodotermes mossambicus), (II) ants (Formicidae), (III) other arthropods, (IV) reptiles, (V) birds, (VI) mammals (VII) grass, (VIII) berries and (IX) non-food items (e.g. bat-eared fox fur presumably ingested when grooming).…”

Sustainable small stock farming and ecosystem conservation in southern Africa: a role for small mammals?

“…Kok and Nel (2004) have found black-backed jackal to be more opportunistic than caracal, reflecting their phylogenetic adaptations to prey acquisition. Kok and Nel (2004) have found black-backed jackal to be more opportunistic than caracal, reflecting their phylogenetic adaptations to prey acquisition.…”

“…The fact that caracal and black-backed jackal occur sympatrically in the small stock areas of southern Africa, share their wide prey spectrum (Rowe-Rowe 1983, Avenant and Nel 2002, Kok and Nel 2004, Loveridge and Nel 2004, Melville et al 2004) and may impact on each other's numbers, poses a real challenge to conservationists, wildlife biologists and farmers. Some farmers and problem animal hunters have already come to the conclusion that the unselective removal of jackal often leads to more damage (de Wet 2002, Genis 2006 le Roux, K. Louw, R. Wilke personal communication), while we expect it also to lead to increased compensatory breeding and immigration.…”