Abstract:
Disturbances that change population structure may evoke transient dynamics
that can be assessed within a demographic resilience framework. Conservation
management interventions are conceptually disturbances that can be evaluated
through such a framework to inform management actions and goals. The Main
Camp in Addo Elephant National Park in South Africa presents a case study.
Here management reduced the size of the elephant (Loxodonta africana) population
by 26%. We compared population growth, modelled trends, constructed
life tables and parameterized population projection matrices from
data collected before, during and after the interventions. The interventions
reduced population size and density, but co-occurring droughts may have
reduced subsequent population growth and stage-specific survival. Transient
dynamics followed the interventions and droughts and were associated with
an unstable stage structure. The effect of adult survival on modelled asymptotic
growth (its elasticity) was greater than a change in fertility. However,
lowered juvenile survival contributed most to changes in transient growth.
Management plans for elephant populations should consider the length of
transients induced by interventions and environmental disturbances such as
droughts. Our approach can benefit the assessment of population responses of
elephants to disturbances such as poaching and persistent droughts elsewhere
in Africa.
