Table 1. Body mass, testes mass and relative testes mass of muroid rodents.
| Species | N | Body mass (g) | Testes mass (g) | Relative testes mass |
| Arvicola terrestris | 5 | 91.56±4.47 | 0.411±0.027 | 0.409 |
| Chionomys nivalis | 6 | 43.64±1.35 | 0.851±0.061 | 1.499 |
| Clethrionomys glareolus | 6 | 25.65±1.47 | 0.401±0.048 | 1.063 |
| Microtus arvalis | 8 | 36.40±3.17 | 0.285±0.023 | 0.577 |
| Microtus cabrerae | 6 | 44.27±2.47 | 0.142±0.025 | 0.247 |
| Microtus duodecimcostatus | 6 | 29.76±1.36 | 0.076±0.013 | 0.179 |
| Microtus lusitanicus | 3 | 17.73±0.88 | 0.093±0.023 | 0.327 |
| Apodemus sylvaticus | 8 | 30.43±1.70 | 0.961±0.054 | 2.236 |
| Mus cookie | 4 | 23.67±0.81 | 0.305±0.032 | 0.861 |
| Mus famulus | 3 | 27.40±0.77 | 0.053±0.007 | 0.134 |
| Mus macedonicus | 3 | 18.40±0.67 | 0.282±0.022 | 0.966 |
| Mus musculus bactrianus | 3 | 18.06±3.04 | 0.175±0.008 | 0.609 |
| Mus musculus castaneus | 3 | 19.50±0.33 | 0.100±0.006 | 0.326 |
| Mus musculus domesticus | 4 | 16.36±0.97 | 0.135±0.005 | 0.506 |
| Mus musculus musculus | 5 | 21.13±1.06 | 0.134±0.003 | 0.411 |
| Mus pahari | 5 | 30.08±0.33 | 0.118±0.007 | 0.277 |
| Mus spicilegus | 5 | 14.49±0.49 | 0.409±0.012 | 1.682 |
| Mus spretus | 5 | 17.01±0.48 | 0.295±0.008 | 1.072 |
Values are mean ± SEM. Relative testes mass was calculated as the ratio of observed testes mass to the predicted testes mass Y. Predicted testes mass Y for each species was calculated following Kenagy and Trombulak's [58] formula for rodents: Y = 0.031X0.77, where X is the observed body mass.