Observation of a p < 10–9 life-history event: implications of record-late caribou birth on ungulate reproductive ecology and field studies

Abstract

Life-history traits in temperate ungulates are highly seasonal, with events corresponding to the seasonal availability of resources. An important example is birth date, with later-born individuals typically having reduced survival compared with those born earlier in the season. Ungulates, especially those whose offspring are at their mother’s heel soon after birth, are typically born in a narrow window of time in late May–early June. In Newfoundland, mean birth date in caribou (Rangifer tarandus (L., 1758); n = 1175) was 31 May. Here, we document a sighting of a caribou calf born ∼25 July on Fogo Island, Newfoundland (∼55 days after the mean birth date). Calving date was estimated using movement rate of the mother and validated by visual observations of the mother. We discuss the implications of this finding as it pertains to caribou ecology, and suggest that studies of ungulate birth date should ensure that observations are continued well past the initial birth pulse to guarantee that a complete picture of ungulate breeding ecology be maintained.