Differences in physiological characteristics of spiny mice on the north- And south-facing slopes of Nahal Oren, Mount Carmel

Throughout the northern part of Israel, the north-facing slopes (NFS) of wadis have more dense vegetation than the south-facing ones (SFS). The main reason for this difference is the high solar radiation absorbed by SFS relative to NFS, and its effects on soil moisture, temperature, and flora. The common spiny mouse Acomys cahirinus serves as an ideal model to examine the effects of these climatic differences on animal physiology, as it inhabits both desert and Mediterranean habitats. We hypothesized that spiny mice, found on both slopes, may respond to these environmental differences by evolving into two separate populations, differing in their physiological capacities. Spiny mice were trapped from SFS and NFS in the lower parts of Nahal Oren, Mount Carmel. The body mass of NFS mice was significantly higher than that of SFS ones. Upon increasing salinity in the diet, this difference disappeared, implying that the kidneys of the SFS mice cope better with aridity. Increased salinity significantly lowers digestibility in both populations, and increases urine osmolarity in NFS mice. Interestingly, the osmolarity of the SFS mice was relatively high to begin with, and did not change with increased salinity. In both groups, a high salt diet affected neither urine volume nor urea concentration.