Shifting prey selection generates contrasting herbivore dynamics within a large-mammal predator-prey web

Shifting prey selection has been identified as a mechanism potentially regulating predator-prey interactions, but it may also lead to different outcomes, especially in more complex systems with multiple prey species available. We assessed changing prey selection by lions, the major predator for 12 large herbivore species in South Africa's Kruger National Park. The database was provided by records of found carcasses ascribed to kills by lions assembled over 70 years, coupled with counts of changing prey abundance extending over 30 years. Wildebeest and zebra constituted the most favored prey species during the early portion of the study period, while selection for buffalo rose in the south of the park after a severe drought increased their vulnerability. Rainfall had a negative influence on the proportional representation of buffalo in lion kills, but wildebeest and zebra appeared less susceptible to being killed under conditions of low rainfall. Selection by lions for alternative prey species, including giraffe, kudu, waterbuck, and warthog, was influenced by the changing relative abundance and vulnerability of the three principal prey species. Simultaneous declines in the abundance of rarer antelope species were associated with a sharp increase in selection for these species at a time when all three principal prey species were less available. Hence shifting prey selection by lions affected the dynamics of herbivore populations in different ways: promoting contrasting responses by principal prey species to rainfall variation, while apparently being the main cause of sharp declines by alternative prey species under certain conditions. Accordingly, adaptive responses by predators, to both the changing relative abundance of the principal prey species, and other conditions affecting the relative vulnerability of various species, should be taken into account to understand the interactive dynamics of multispecies predator-prey webs.     

Age,size, dominance and reproduction among male kudus: mating enhancement by attrition of rivals

Summary Size dimorphism with males larger than females has been related to the benefits for males of enhanced dominance and hence reproductive success. However, mating gains must outweigh the fitness costs of deferred reproduction and the mortality associated with further growth. The relationships between male age, size and reproduction were assessed for greater kudus (Tragelaphus strepsiceros) in the Kruger National Park in South Africa. Individually identifiable animals were monitored over 10 years, with detailed observations made during six breeding seasons. In the non-breeding season males formed loose all-male groups. Horn grappling and low intensity agonistic interactions fostered dominance rankings. Dominance was age-graded, until males reached full weight at 6 years of age. Males aged 6 and 7 years monopolized courtship and mating, but 5-year-old males secured about 10% of mating opportunities. Few males survived beyond 7 years. Male mortality rate rose steeply with age, so that the functional sex ratio of fertile females per mature male was about 14:1. During the breeding season many female groups remained unattended by a mature male. Reproductive sorting among males occurred largely through variation in survival to full size and maturity. Increased size enhances fighting success and hence dominance. Further growth ceases when the functional sex ratio exceeds the number of mating opportunities that males can effectively achieve during a breeding season. Predation amplifies the mortality cost of continued growth. In the absence of large predators, male-male interactions may be atypically exaggerated.     

A prospective health impact review of the redevelopment of Central Manchester Hospitals

Health Impact Assessment (HIA) is increasingly being acknowledged as an important tool for considering the health implications of projects and programmes of activity at local, national and international levels. However, standard HIA tools can be difficult to apply when the policy of programme under consideration is particularly complex and intertwined or where significant time, resource and skill constraints are involved. This paper describes a Health Impact Review (HIR) of the plans for a major redevelopment of Central Manchester Hospitals (England). This approach to HIA drew not only from HIR but also from Integrated Impact Assessment (IIA) in order to produce a summary of the most significant health impacts of a policy, programme or project in a more timely and cost-effective way. This example highlights the potential for involving Local Authority Overview and Scrutiny Committees in the HIA process as a way of ensuring that the recommendations of HIA are mainstreamed as part of the ongoing development of projects.