Good start to winter for ungulates..?

[Pemby_mess]

I assume you mean 'I doubt there is an area where wolves CAN'T operate in'?
I hear what you're saying, but also spent a pile of time around the monashees, selkirk and purcells back in my backcountry snowboarding days. Can't remember many instances I could operate without snowshoes, meaning a canine would likely have the same issue. All my buddies that still have the powder bug now rock touring skis or split boards, similar experiences snow wise.

Another good example would be my favourite Stone Sheep area. Talked to a fellow involved in a 5 year sheep study in that area. They found winter predation was much less on the higher snowfall winters. The sheep concentrate the northern wind swept grass slopes, snow accumulation from valley bottom up prevents dogs from reaching them. Little bit different scenario but it makes some sense.

I know any area in then Selkirks where the moose thrive up high in 10ft+ snow pack. They live on alder bark all
winter safe from the dogs. I was shocked when I stumbled on them years ago snowshoeing around slide paths with a spring Grizz tag.

I know one would think that as the temp warms up and snow levels settle it would be a cakewalk for dogs. I find unless it actually rains then freezes right after it's not so much the case. Heavy settled snow can actually dry out quite easily following a cold snap, without that detrimental crust forming.

Many variables, hard to say for certain.

As a general rule in this part of the world:

Northern mountain slopes are considered "lee" to the wind, and therefore accumulate deeper snowpacks due to wind action. Southerly "aspects" are "wind swept" by the prevailing winds. More feed will typically be available year round on southerly aspects.

avalanche paths are more numerous on south facing slopes, and larger, but run less frequently on the North sides.

Deeper snowpacks will consolidate and settle to a greater degree (and more quickly after additional snowfalls) than shallow snowpacks with all else equal. Total depth of snowpack has little to do with the surface character and "depth of penetration", but a deeper snowpack being better consolidated usually has less foot penetration absent any crusts on the south sides.

crusts form as a consequence of liquid precipitation, sun affect, temperature spikes, and wind scouring. Crusts break down from prolonged cold temps like you mention.

[Pemby_mess]

The winter weather is generally going to exert significant variance on the snowpack and feed availability according to aspect, elevation, and region. This is why having diverse habitat availability and interconnectivity is so important to ungulate survival.

We'll often see breakable crust conditions within narrow elevation bands, not present above and below. If ungulates can move off of the aspect and elevation where they occur, they will prove more resilient to predation. If there are habitat features that keep them confined, or the condition is more widespread than is typical, that population will be in trouble.

one of the facts about the snowpack that has recently come to light where it concerns ungulates is winter time road use. In lots of mountainous regions ungulates will move to where both the terrain and the snowpack protect them from predation based on the variance in conditions at the time. When snow machines compact snow, it gives wolves and other predators express access into all regions, elevations, and aspects of the mountains; meaning the ability of snowpack conditions and terrain features to protect from predation is reduced.

[Bugle M In]

All good points.
The example I was giving was like the day up in the EK.
It snowed about 12", but it was all real Fluffy stuff, and if you had ten feet of that, then yes, wolves cant operate in that, they fall thru as well.
But a day later, it had warmed up, and the weight of the snow itself had caused it to go from 12" to more like 4".
If you get that type of "Compacting" and repeated days like that, even if you have 10 feet of it, the wolves can
operate.

The bigger concern for ungulates is freezing rain, making it impossible for them to get to the feed.
That's why you will see that they go after the bark so much those years, cause they are starving (not talking moose here).

So, frozen Ice Ground due to rain which freezes and then throw a whole bunch of snow on top of that, in a real quick time line is definitely a recipe for disaster.

I think I also recall that back then, the game just had a hard time trying to find "routes" out of there as well.
Things sure are getting any easier for Ungulates, that's for sure.

[boxhitch]

Then there is the mid and high elev logging going on, eating up former winter ranges. Tough for critters to adapt in times of rapid change
Deer need big trees in snow zones

[.264winmag]

Not my info, just relaying the studies' findings. In case of the sheep there is less snow accumulation on the upper portion of the northern aspects because of the wind and lack of sun affecting snowpack. Below the accumulation is higher helping keep preds out. The southern aspects in the area get cooked off in the late summer and fall, leaving the north the place to be for good wintering grub. And where all the netting/collaring went on throughout winter. Perhaps an anomolly this area.

Moose are absolutely on the southern slide paths.

[dapesche]

Sounds plausible B but I haven't seen any hard info correlating weather events and deer pops, I doubt these things are monitored.
With the large die-off of '96 folks were reporting finding groups of dead deer iirc, haven't heard of such a thing again.

This last winter had snow pack at 150% of normal in many parts of BC, anyone hear word about findings of an inordinate number of dead?

Based on podcasts, the last couple years of winters just south of the border led to a tremendous amount of winterkill. I'm assuming we were no different. They just seem to be able to keep better track due to funding.

[Pemby_mess]

All good points.
The example I was giving was like the day up in the EK.
It snowed about 12", but it was all real Fluffy stuff, and if you had ten feet of that, then yes, wolves cant operate in that, they fall thru as well.
But a day later, it had warmed up, and the weight of the snow itself had caused it to go from 12" to more like 4".
If you get that type of "Compacting" and repeated days like that, even if you have 10 feet of it, the wolves can
operate.

The bigger concern for ungulates is freezing rain, making it impossible for them to get to the feed.
That's why you will see that they go after the bark so much those years, cause they are starving (not talking moose here).

So, frozen Ice Ground due to rain which freezes and then throw a whole bunch of snow on top of that, in a real quick time line is definitely a recipe for disaster.

I think I also recall that back then, the game just had a hard time trying to find "routes" out of there as well.
Things sure are getting any easier for Ungulates, that's for sure.

the rate of consolidation (settlement) or "compaction" is determined by the temperature profile of the snowpack. In a deep snowpack with a relatively smooth, or "shallow" temperature gradient; settlement will be rapid and the snowpack "firms up" quickly. Think coastal snowpack here. You can have more than 50 feet of accumulation in some areas, but be able to walk on it with no snowshoes. In these conditions, both predator and prey can move through the snow fairly naturally.

In a snowpack with a "steeper" temperature gradient, light fluffy snow will stay light and fluffy. What's more, previously settled snow within the historical snowpack will "unconsolidate". In other words, it will undergo faceting and become weak and unsupportive leading to deeper hoof and paw penetration.

temperature gradients are often not consistent throughout the snowpack; nor throughout time and space. You'll have layers within the snowpack that are consolidated, and other layers that were formulated in cold temps that remain cold and dry once buried. These layers will often continue to weaken when the weather is not promoting settlement - like lots of successive cold clear nights.

A backcountry skier's worst nightmare, and also that of deer; is something called an "upside-down snowpack". A weak, unsupportive crust is one example of this, but it can also occur from a storm that simply warms up a few degrees from cold to not so cold in it's duration. Here you'll get a firm "storm slab" overlying weak punchy layers that don't carry any significant weight. If this condition persists due to steep snowpack temperature gradients, wolves can travel 40-100km in a day over the surface, whereas deer might be luck to gain 5k in an attempt to adapt and evade. so they'll be run down.

Tough travel conditions also mean more energy expended in the perennial search for food and safety. So freezing rain is not necessary to render food supplies inadequate, although neither would something like that help. There are much more common winter weather phenomena that would cause deer to exhaust their food supplies. Anything that throughs their energy balance out will do it.

Any rain falling on snow in the mountains typically freezes, unless the entire season's snowpack has transitioned isothermal - which is another snowpack phenomena lethal to ungulates

[Pemby_mess]

Not my info, just relaying the studies' findings. In case of the sheep there is less snow accumulation on the upper portion of the northern aspects because of the wind and lack of sun affecting snowpack. Below the accumulation is higher helping keep preds out. The southern aspects in the area get cooked off in the late summer and fall, leaving the north the place to be for good wintering grub. And where all the netting/collaring went on throughout winter. Perhaps an anomolly this area.

Moose are absolutely on the southern slide paths.

well, as a "rule of thumb" it doesn't really make sense, because high elevation North slopes aren't typically subject to wind scour by prevailing winds. You'll see wind scouring on southern aspects, even a complete absence of snow in the windiest areas. Wind-loading is occurring on northerly slopes - think heavy glaciation; a consequence of nearly constant wind loading throughout the millennia.

It does make sense that the best vegetation for feed be present on Northerly aspects due to Southern aspects being "baked off" over the summer.

One thing that would run counter to the rule of thumb, is sustained "Northern outflow" conditions. This is when the prevailing winds reverse due to an "outflow" event of Arctic high pressure. This will will scour the previously wind loaded north aspects, throwing all the snow load onto the previously scoured South aspects. Some winters are characterized by more outflow events than others. Mountain ranges at higher latitudes have more occurrences of these events than in regions at lower latitudes.

[.264winmag]

Just picture the upper portion of the northern aspects, hardly any accumulation. It piles up not far below. If you seen this spot on a map it would make more sense I think. It's about as far NE as it gets for stones. Apparently not the only location that has these tendencies for sheep.

[Pemby_mess]

Just picture the upper portion of the northern aspects, hardly any accumulation. It piles up not far below. If you seen this spot on a map it would make more sense I think. It's about as far NE as it gets for stones. Apparently not the only location that has these tendencies for sheep.

yeah, something is not making sense. If i'm standing at the top of an East-West running ridge, where the South aspect is on my left hand side, and the North on my right hand; it's not uncommon to have bare rock all the way down to the tree line on the South side, but have 5 meters or more of consolidated snow immediately on the North side of the ridge. North side is lee every where in the Northern hemisphere - and is where the snow being carried by the wind drops out and accumulates. One alpine terrain feature that will sometimes scour on North sides, are moraines. Just cause they are steep and stick out of the surrounding snow pack.

in fact, the higher you go in elevation, the more this effect will intensify. The old growth forests on both south and north sides will have similar depth of snowpack; as you go up to tree line, Southerly aspects start showing more wind affect; and as you get up high in the alpine, the wind affect on snow will be complete: the wind will typically carry all the snow on the windward South side, and dump it onto the North. You can be on a peak with 100k winds and by the time you drop 10 meters down onto the sheltered North side, you might not feel a lick.

in addition, the South alpine side is exposed to sun. So while the sun doesn't so much melt the snow off of the peaks, it does contribute to something called "sublimation", which is essentially what happens when snow evaporates. That won't occur at the same rate on a North aspect where the snow remains unaffected by sun year round.