Wait, what?: "actual [polar bear] cub survival often seems to have a negative correlation with good ice years"

Polar Bear Alley – Churchill’s Bears and Hudson Bay Winter

Obviously,
the early freeze-up and the cold temperatures will translate to thicker
ice on the bay than in previous years and likely a longer ice season
come this spring. That is fairly goods news as our bears do most of
their hunting between April and the end of June/early July.

The bad news is that actual cub survival often seems to have a negative correlation with good ice years
(although cubs that do survive will end up in better shape) (Stirling
et al, 1999). From what I can gather, this is usually due to a severe
winter (like the one we have) and the lack of insulation in not just the
cubs fat layer but, moreso, the mother. A bit of a disturbing trend
this winter was that two of the bears tracked by WWF were of prime age
and beginning the season with only one cub… so we’ll see.
...
So, I have said it before but if there is anything Churchill’s bears need right now is ‘above average’ warm spring.
With this heavy ice and warm temperatures, it really could be a bonanza
year for western Hudson Bay. If this cold snap returns, well, its
strangely not great news. What we really want is a cold
November/December, a warm January-March and then a cold April-July…
that’s kind of best-case scenario.