| I quantified several aspects of hibernacula use and estimated home ranges of desert tortoises (Gopherus agassizii) in the San Pedro Valley, Arizona. Tortoises hibernated primarily on steep southerly slopes. Hibernacula included burrows in silt, silt with loose gravel, diatomite and/or diatomaceous marl, and beneath an ash layer, often in conjunction with live vegetation, dead and downed vegetation, and packrat (Neotoma albigula) nests. Male tortoises used longer hibernacula than females (p < 0.02). Female maximum hibernacula temperatures were consistently higher than male maximum hibernacula temperatures, but the difference was not significant (0.05 < p < 0.10). Female minimum hibernacula temperatures were significantly lower than males (p < 0.001) and female hibernacula temperatures fluctuated over a significantly wider temperature range than males (p < 0.01). Hibernacula used by males provided greater thermal buffering than those used by females. Duration of hibernation was positively correlated with shelter length. Home-range estimates did not differ significantly between males and females. |
