Probably an increase in the population in their main predator or over hunting by humans
If there are more lions than deer, the lion population may increase initially due to more available prey. However, this could lead to over-predation and eventually a decrease in the deer population. This may result in a decrease in the lion population due to a lack of food supply.
Well for an example, if the number of hunters increase in the forests then the population of deer will decrease and the other predators of the deer have nothing to feed on and will eventually starve.
It Deceases Because The Habit Destruction & Deer
The deer would not have enough food and start to starve to death which would cause the population to decrease locally. They may migrate toward other areas not as impacted by the drought, or spread out more.
A biotic factor that could limit the size of a deer herd is the availability of food sources. If there is not enough food to support a larger herd, this could lead to competition for resources, malnutrition, and a decrease in reproductive success among the deer population.
Humans hunt the deer and cause the deer's population to decrease. We also take away their habitat by chopping down forests.
There are many contributing factors that could be the cause for a decrease in fox population. Over population, not enough food, disease, or over hunting or poaching any of these could be the reason for a decrease in the population.
if the limited factors changes than the deer populations will increase and will have a more impact on wolves.The wolves will be more as compare to deer and will feed on deer .If there are less deer the wolves will die out of starvation or will go to some other place to get food .plants will saved by overgrazing and there will no balance in nature.
It's a double-edged sword, really. To me, it's best to save deer when the population is quite small, smaller than it should be. But when the deer population has increased to more than what it should be (also called overpopulation), then deer should be hunted to decrease the numbers.
an increase in the spider population
If the deer population increased fivefold, it could lead to overgrazing of vegetation, which could disrupt the ecosystem by decreasing plant diversity and altering habitats. This could also result in more frequent conflicts with humans, such as vehicle collisions and damage to crops. Additionally, an increase in deer population could potentially lead to an increase in disease transmission within the deer population.
Death and migration are factors that can decrease hare population.