Strategies of protected area use by Asian elephants in relation to motivational state and social affiliations.

Animals' space requirements may vary according to life-history and social considerations. We observed 516 wild adult Asian elephants from both sexes, over 9 years, to investigate how life-history traits and social behavior influence protected-area (PA) use at Udawalawe National Park, Sri Lanka. Male PA-use, quantified in terms of average between-sightings-interval (BSI), was significantly influenced by the interaction of age class and motivational state (i.e. reproduction vs. foraging). Musth lengthened with age, with a median of 24.5 days for ages 21-30, 32.5 days for ages 31-40, and 45 days for those > 40. A minority (11%) used it exclusively during musth, while others used it exclusively for foraging (44%) or both (45%). Males using it in both states and older musth-only males were more likely to be seen across years. There were 16 social communities containing between 2-22 adult females. Females' BSI was significantly influenced by social ties, but this relationship was weak, because members of social communities do not necessarily disperse together, resulting in high individual variation in space-use. Inter-annual variability in sightings among individuals of both sexes indicates that around ¾ of the population is likely non-residential across years, challenging the prevailing fortress-conservation paradigm of wildlife management.

Modulation of human malaria transmission by anti-gamete transmission blocking immunity.

Natural Plasmodium vivax malaria infections in man evoke anti-gamete transmission blocking antibodies which influence the infectivity of malaria patients to the vector mosquito. In this study, entomological, immunological and parasitological data obtained through the monitoring of an epidemic of human vivax malaria in Sri Lanka were used in a mathematical simulation to assess the effect of naturally induced transmission blocking immunity on malaria transmission. A mathematical model to describe malaria transmission accounting for transmission blocking immunity was developed from the basic differential equations originally stated by R. Ross and the epidemic was simulated using the available data. An attempt was made to predict the monthly malaria incidence by means of the mathematical simulation, with and without accounting for transmission blocking immunity. A plausible mathematical solution of the epidemic could be obtained when transmission blocking immunity was accounted for, and it was not possible to obtain such a plausible solution in the absence of immunity. Thus, the postulated occurrence of transmission blocking immunity was essential to describe adequately this malaria epidemic, indicating that, at least in epidemic situations, naturally occurring transmission blocking immunity has a controlling influence on malaria incidence.