COMPARATIVE ASPECTS OF THE THERMAL BIOLOGY OF THE CAPE SPINY MOUSE, ACOMYS SUBSPINOSUS, AND THE COMMON SPINY MOUSE, A. SPINOSISSIMUS

ABSTRACT

Thermal characteristics of Acomys subspinosus, from a disjunct population in the southwestern Cape separated from the more widely-dispersed Acomys populations in the rest of Africa, and A.spinosissimus, which has a southern central distribution in Africa, were investigated and compared with other Acomys species. A. subspinosus has a higher-than-expected resting metabolic rate (RMR) for its body mass (2.587 ± 0.387 ml O₂g⁻¹ h⁻¹; W_b = 32.3 ± 3.2 g) and a higher RMR than A. spinosissimus, which has a lower-than-expected RMR (1.634 ±0.182 ml O₂ g⁻¹ h⁻¹; W_b = 27.0 ± 2.2 g) for its body mass. Each species has a high, narrow thermoneutral zone. Evaporative water loss (EWL) increased with ambient temperature in both species. However, A. subspinosus increased EWL at a higher rate, two times greater than that of A. spinosissimus. Temperature regulation and thermal conductance are compared and discussed.