One biotic factor that could increase the deer population's carrying capacity is the availability of food. If there is an abundance of food, such as vegetation and plant matter, then deer will have an easier time finding enough food to survive and reproduce. This can lead to higher birth rates and better overall health for the population, which can increase the carrying capacity. Additionally, if there is more food available, it can also attract more deer to the area, further increasing the population size that can be supported by the available resources.