COPROPHAGY RESPIRATION
The larynx is placed high in the oropharynx where it can directly access the nasopharynx so all these species are obligate nose breathers (Vaughan 1986b) (Fig. 10.13). Being animals of small body weight they have higher oxygen demands than larger mammals.
Increased oxygen intake is facilitated not by larger lungs but by a number of other modifications.Rabbits and rodents have high chest wall compliance and vital capacity and low residual lung capacity. This enables them to expand their lungs well to draw in more oxygen and expel maximum air with each breath. They also have more alveoli of thinner diameter to allow maximum oxygen exchange. For example the diameter of the alveoli of the Syrian hamster is 35-75 Um in contrast to 200 in the cat and 400 in the sedentary sloth. Shorter airways and high respiration rates also increase oxygen intake (Donnelly 1990).
Coprophagy (from the Greek “to eat dung”) is a behavior where an animal reingests its own excreted feces and it has been observed in the rabbit, rat, mouse, hamster, guinea pig, and chinchilla. It is more correctly called cecotrophy. While herbivorous hindgut fermenters like the rabbit, guinea pig, and chinchilla show very active cecotrophy, it is exhibited to a lesser extent in the more omnivorous rat, mouse, and hamster. It can increase during pregnancy and lactation in order to increase the supply of vitamin B12 and folic acid. Although modern diets mean that coprophagy is unnecessary for survival, it is an innate behavior stimulated by anal reflex (Ebino 1993).