Moose (Alces alces) parturition dates, Sweden

In northern environments, the period of access to high-quality forage is
limited, exerting strong selective pressure to optimize the timing of
parturition. We analysed timing and variation in moose parturition dates
of 555 females at 18 study sites across 12ᵒ of latitude (56-68ᵒ N, 1,350
km) in Sweden. We found evidence for a spatial match of parturition timing
to vegetation onset, but no evidence that moose adjust parturition to
vegetation onset in a given year. We found a breakpoint at 64ᵒ N. Despite
adaptation across latitudes, temporal divergences occurred. Females
<64 ᵒN calved after vegetation onset and females >64 ᵒN
calved before. Here, parturition before vegetation onset might be a
strategy to optimize forage utilization time with the very short growing
season. Highly seasonal environments such as at higher latitudes may make
it advantageous to adapt parturition towards long-term climatic patterns
by matching the most favourable period. Given the direction of temporal
divergence, our study suggests that climate change may have less of an
impact on moose parturition at northern latitudes than southern latitudes.