Can we use the young : female ratio to infer ungulate population dynamics? An empirical test using red deer Cervus elaphus as a model

摘要: Summary 1 Management decisions for exploited species often rely on count ratios, such as the young to adult female ratio a proxy of birth rate, and decrease in between yearling females year t+ 1 young : female t obtain juvenile survival. However, reliability estimates has yet be demonstrated. 2 We investigated consistency method by using observations individually marked red deer. These were known have raised their calves weaning successfully. We compared temporal variation proportion with calf at heel from ratios probability observing its mother animals. 3 The observed decreased over time (from 0·43 early May 0·15 March). This measure was influenced individual interactive effects habitat type, although there no direct relationship density vegetation cover. 4 The seen assessed counts did not correspond heel, given that she successfully weaned autumn (estimated observation). The highest September (0·4) prior rut lowest just after season (0·08) during (0·18). 5 The pattern mother, calf, reflected changes mother–calf bond weaning, rather than offspring mortality or pregnancy rates. variations pair field may lead strong biases ratio-based methodologies. 6 Synthesis applications. study important implications management ungulate populations when are based ratios. Our results indicate count-based vital rates misleading, especially closed habitats. Pregnancy rate survival both key parameters detecting density-dependence responses. Reliable obtained animals foetus sampling more accurate. Alternatively, yearly monitoring body mass bone length coupled an index grazing pressure would improve assessment population dynamics.