Response of lion demography and dynamics to the loss of preferred larger prey

Large carnivores are experiencing range contraction and population
declines globally. Prey depletion due to illegal offtake is considered a
major contributor, but the effects of prey depletion on large carnivore
demography are rarely tested. We measured African lion density and tested
the factors that affect survival using mark-recapture models fit to six
years of data from known individuals in Kafue National Park (KNP), Zambia.
KNP is affected by prey depletion, particularly for large herbivores that
were preferred prey for KNP lions a half-century ago. This provides a
unique opportunity to test whether variables that explain local prey
density also affect lion survival. Average lion density within our study
area was 3.43 individuals per 100 km2 (95% CI: 2.79 – 4.23), which was
much lower than lion density reported for another miombo ecosystem with
similar vegetation structure and rainfall that was less affected by prey
depletion. Despite this, comparison to other lion populations showed that
age- and sex-specific survival rates for KNP lions were generally good,
and factors known to correlate with local prey density had small effects
on lion survival. In contrast, recruitment of cubs was poor and average
pride size was small. In particular, the proportion of the population
comprised of 2nd year cubs was low, indicating that few cubs are recruited
into the sub adult age class. Our findings suggest that low recruitment
might be a better signal of low prey density than survival. Thus,
describing a lion population’s age structure in addition to average pride
size may be a simple and effective method of initially evaluating whether
a lion population is affected by prey depletion. These dynamics should be
evaluated for other lion populations and other large carnivore species.
Increased resource protection and reducing the underlying drivers of prey
depletion are urgent conservation needs for lions and other large
carnivores as their conservation is increasingly threatened by range
contraction and population declines.