Panthers and leopards prey on deer in an ecosystem. For unknown reasons, the population of leopards increased drastically. What are the likely effects of this change on the species?

There could be one of two answers to this:

When a species' number drastically increases, it could mean that the amount of availible resources for that species has increased, OR, the competitor to the species has decreased. The answer that is most probable in this situation is that the number of panthers has decreased, causing there to be more deer for the leopards to prey on. Before this occurred, the leopards and panthers probably competed to prey on deer. If there are significantly less panthers around, more leopards will be able to prey on the deer in the ecosystem. This can also decrease the deer population and make more competition for the panthers, as their numbers would be small compared to those of the leopards.