Divergence in parturition timing and vegetation onset in a large herbivore-differences along a latitudinal gradient.

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 (Alces alces) parturition dates of 555 females at 18 study sites across 12° of latitude (56-68° N, 1350 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 64° N. Despite adaptation across latitudes, temporal divergences occurred. Females below 64° N calved after vegetation onset and females above 64° N 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.

A wasting syndrome in Swedish moose (Alces alces): background and current hypotheses.

In the 1980s, people in Sweden frequently responded to moose (Alces alces) found dead or in poor physical condition. The number of moose submitted for routine investigations to the National Veterinary Institute (SVA) increased tenfold and the hunters in Alvsborg County were especially concerned. Later, a complex wasting syndrome was described and reports of moose suffering from the syndrome have been collected since 1991. Today, there is no definitive answer as to the underlying causel(s) of the syndrome, but there are several plausible hypotheses that can be divided into two groups: food-related and host-parasite related. The food-related hypotheses are postulated to have any of the following ultimate causes: acidification/liming, browser density/food production or pollution. Our view is that few of the hypotheses have been critically tested. Most of the hypotheses are supported by some observations, which is to be expected because these are post-hoc attempts to explain these very observations.