The geographic range of chytridiomycosis is difficult to ascertain. If it occurs, the disease is only present where the fungus "B. dendrobatidis" is present. However, the disease is not always present where the fungus is. Reasons for amphibian declines are often termed ‘enigmatic’ because the cause is unknown. Why some areas are affected by the fungus while others are not is not fully understood. Oscillating factors such as climate, habitat suitability, and population density may be factors which cause the fungus to infect amphibians of a given area. Therefore, when considering the geographic range of chytridiomycosis, the range of "B. dendrobatidis" occurrence must be considered.