I believe the answer is environmental pollution
Independent of whether an organism is an endotherm or ectoderm, the least reliable indicator of an animal's metabolic rate is the amount of water consumed in one day. The metabolic rate is the speed at which chemical reactions take place in the body and varies because of several factors including age, gender and inherited factors. It is also affected by the proportion of muscle to fat in the body , amount of exercise and other physical activity.
