Figure 1

(A,B) Drawings of the semifossorial African giant pouched mole rat (Cricetomys gambianus) (A) which partly inhabits open burrows and the underground dwelling (subterranean) Nigerian mole rat (Cryptomys foxi) (B). Compared to the air above the ground, that in the underground burrows generally contains relatively high concentrations of carbon dioxide (CO2) and low ones of oxygen (O2). (Figures drawn by the investigators).