Data from: Disease, predation and demography: assessing the impacts of bovine tuberculosis on African buffalo by monitoring at individual and population levels

1. Understanding the effects of disease is critical to determining
appropriate management responses, but estimating those effects in wildlife
species is challenging. We used bovine tuberculosis (BTB) in the African
buffalo Syncerus caffer population of Kruger National Park, South Africa,
as a case study to highlight the issues associated with estimating chronic
disease effects in a long-lived host. 2. We used known and radiocollared
buffalo, aerial census data, and a natural gradient in pathogen prevalence
to investigate if: (i) at the individual level, BTB infection reduces
reproduction; (ii) BTB infection increases vulnerability to predation; and
(iii) at the population level, increased BTB prevalence causes reduced
population growth. 3. There was only a marginal reduction in calving
success associated with BTB infection, as indexed by the probability of
sighting a known adult female with or without a calf ( P = 0·065). 4.
Since 1991, BTB prevalence increased from 27 to 45% in the southern region
and from 4 to 28% in the central region of Kruger National Park. The
prevalence in the northern regions was only 1·5% in 1998. Buffalo
population growth rates, however, were neither statistically different
among regions nor declining over time. 5. Lions Panthera leo did not
appear to preferentially kill test-positive buffalo. The best (Akaike’s
Information Criterion corrected for small sample size) AIC c model with
BTB as a covariate [exp( β ) = 0·49; 95% CI = (0·24–1·02)] suggested that
the mortality hazard for positive individuals was no greater than for
test-negative individuals. 6. Synthesis and applications . Test accuracy,
time-varying disease status, and movement among populations are some of
the issues that make the detection of chronic disease impacts challenging.
For these reasons, the demographic impacts of bovine tuberculosis in the
Kruger National Park remain undetectable despite 6 years of study on known
individuals and 40 years of population counts. However, the rainfall and
forage conditions during this study were relatively good and the impacts
of many chronic diseases may be a non-linear function of environmental
conditions such that