Food as a limiting factor for small rodent numbers : Tests of two hypotheses.

摘要: 1. Two hypotheses relating small rodent density variations to their food conditions were tested by attempts refute derived predictions on and dynamics of populations. One assumes an independent rhythm in plant production the other gradual overgrazing. The findings also compared with from self-regulation 2. vole species, representing one herbivore partial granivore, sampled South, Central North Sweden 1971-1975. A two year population peak was found both species Sweden, a no obvious at all South Sweden. 3. Weather conditions, primary various plants chemical composition examined same regions. Food improved for least herbivorous rodents during increases before peaks Similar annual appeared without any accompanying numerical changes 4. In certain respects neither hypothesis could be refuted. However, observations did not favour ideas self-regulation. Thus new is proposed. It that areas predators show dynamic balance below resource limitation. disturbed habitats or much snow, predation difficult. There may overexploit but time affected several-year plants.