ICM Contest Problem
When is Enough, Enough?
if a habitat is undesirably changed by elephants, then their
removal should be considered -even by culling." National
large National Park in South Africa contains approximately 11,000
elephants. Management policy requires a healthy environment
that can maintain a stable herd of 11,000 elephants. Each year
park rangers count the elephant population. During the past
20 years whole herds have been removed to keep the population
as close to 11,000 as possible. This process involved shooting
(for the most part) and occasionally relocating approximately
600 to 800 elephants per year.
there has been a public outcry against the shooting of these
elephants. In addition, it is no longer feasible to relocate
even a small population of elephants each year. A contraceptive
dart, how-ever, has been developed that can prevent a mature
elephant cow from conceiving for a period of two years.
is some information about the elephants in the Park:
- There is
very little emigration or immigration of elephants.
- The gender
ratio is very close to 1:1 and control measures have endeavored
to maintain parity.
- The gender
ratio of newborn calves is also about 1:1. Twins are born
about 1.35% of the time.
- Cows first
conceive between the ages of 10 and 12 and produce, on average,
a calf every 3.5 years until they reach an age of about 60.
Gestation is approximately 22 months.
- The contraceptive
dart causes an elephant cow to come into oestrus every month
(but not conceiving). Elephants usually have courtship only
once in 3.5 years, so the monthly cycle can cause additional
- A cow can
be darted every year without additional detrimental effects.
A mature elephant cow will not be able to conceive for 2 years
after the last darting.
- Between 70%
and 80% of newborn calves survive to age 1 year. Thereafter,
the survival rate is uniform across all ages and is very high
(over 95%), until about age 60; it is a good assumption that
elephants die before reaching age 70.
- There is
no hunting and negligible poaching in the Park.
park management has a rough data file of the approximate ages
and gender of the elephants they have transported out of the
region during the past 2 years. This data is available here:
no data is available for the elephants that have been shot or
remain in the Park. Your overall task is to develop and use
models to investigate how the contraceptive dart might be used
for population control. Specifically:
Task 1: Develop
and use a model to speculate about the likely survival rate
for elephants aged 2 to 60. Also speculate about the current
age structure of the elephant population.
Task 2 : Estimate
how many cows would need to be darted each year to keep the
population fixed at approximately 11,000 elephants. Show how
the uncertainty in the data at your disposal affects your estimate.
Comment on any changes in the age structure of the population
and how this might affect tourists. (You may want to look ahead
about 30-60 years.)number of elephants to be darted? Comment
on the trade-off between darting and relocation.
Task 4 : Some
opponents of darting argue that if there were a sudden loss
of a large number of elephants (due to disease or uncontrolled
poaching), even if darting stopped immediately, the ability
of the population to grow again would be seriously impeded.
Investigate and respond to this concern.
Task 5 : The
management in the Park is skeptical about modeling. In particular,
they argue that a lack of complete data makes a mockery of any
attempt to use models to guide their decisions. In addition
to your technical report, include a carefully crafted report
(3-page maximum) written explicitly for the park management
that responds to their concerns and provides advice. Also suggest
ways to increase the park managers confidence in your model
and in your conclusions.
Task 6 : If
your model works, other elephant parks in Africa would be interested
in using it. Prepare a darting plan for parks of various sizes
(300-25,000 elephants), with slightly different survival rates
and transportation possibilities.