The Phenomenon of Mass Consumption of Carbonate Rocks by Wild Ungulates in the Spurs of the Primorsky Range on Lake Baikal

The relevance of this study lies in the systematic investigation of the causes of geophagy. Geological and hydrobiogeochemical studies were conducted in two areas on the western coast of Lake Baikal (spurs of the Primorsky Ridge), where wild ungulates consume carbonate rocks. It was established that these rocks contain various mineral forms of rare earth elements that are readily extracted under slightly acidic conditions (HCl, pH 2). Local landscapes are notable for an unusual plant-food Ca : Mg : P ratio of 3 : 1 : 1 (compared with the norm of 0.6 : 1 : 1) and extremely low contents of rare earth elements (average sum of Y and Sc = 0.25 ± 0.11 mg/kg). The average Na content, extracted from carbonate kudurites under slightly acidic conditions across eight samples, is 244 mg/kg, slightly exceeding that in dry vegetation. The average value of extractable rare earth elements (13.46 mg/kg) is more than 50 times higher. Field and laboratory studies, including a review of the literature on the role of rare earth elements in mammals, suggest that ungulates’ consumption of carbonate rocks is driven by their need for specific rare earth elements essential for the normal function of the neuroimmune-endocrine system.