A flea and dog are an example of Choose... Commensalism herbivory mutualism parasitism , because the flea irritates the dog's skin and feeds on its blood. Certain bacteria live in the digestive tract of humans, and their relationship is an example of Choose... Mutualism commensalism herbivory parasitism because the bacteria help humans to break down the food they eat. Cattle egrets eat insects off the back of an elephant, which is an example of Choose... Erbivory parasitism mutualism commensalism because the cattle egrets benefit without either harming or helping the elephants.