Threats, Competitors - and Damage

Natural prey and competition

The moose falls - despite of his high short-distance speeds - prey to bears and wolves, very seldomly to lynx, cougar and wolverine. Up to to 75% of newly born moose calves can be eaten by bears in the first 8 weeks of their live ! Usually about 2/3 survive their predators in the first and most critical year. In Denali National park for example the calf mortality is 80-90%, mainly caused by brown bears.

While the smaller black bear (Ursus americanus), who shares the same territory mainly goes for smaller moose or youngborn, the Grizzly (Ursus arctos) can also hunt for grown moose bulls. Both species prefer calves and ill moose.

Wolves (Canis lupus) attack fully grown moose mainly in case their prey is ill, old or weak, but calves are always welcome in their diet, especially if separated from their mothers. Only if hunting in huge packs of wolves they can attack grown bull moose with a fair chance to win. Wolve packs actually have a good chance to surround and kill a moose in deep snow, when he gets unable to escape -actually make any fast moves- and to defend himself.  That can also be seen as one reason they lay down flat in snow storms and let themselves cover with snow. Wolves don't spum moose died of other causes either. 

Other enemies of especially ill, hurt or very young moose/calves are the cougar (Felis concolor) mainly hunting calves/yearlings and even wolverine (Gulo gulo) and lynx.

Competition is to be seen related to food: The muskrat enjoys water plants as much as the moose does. And other deer and rabits compete when it comes to shrubs and trees.

They usually peacefully co-exist with other big game - except during the rut.  

Moose defense

Moose can strike back with both front- and backfeet with high precision - regard them as lethal weapons. Broken bones and death as consequence for the aggressors are common taking the power and size of the moose into account.

Anyhow escape is a moose's best chance to survive: Long legs to just step over huge obstacles (see also in section " Motion") while the chaser has to use a lot of energy to overcome those. Obstacle height of 60-90 cm are perfect for the escape. As you won't find such obstacles in open land, moose are mostly in territories with forest, shrubs ..., which they know by heart for a successful flight.
Moose also use the possibility to hide after a while, fly with high speed with up to 60 km/h over free planes or to get into flat water, where they can still defend themselves with the legs, but the much lower predators already have problems. They don't use deep water for defense, where wolves could attack efficiently and the moose cannot defend at all.
They sometimes even circle the enemy silently.

They have a fair chance to escape due to their well developped senses: "See, Hear, Smell" - in order to early detect danger and to retract themselves into the forest.

Moose cows always protect their calves, who stay close to their mothers and don't flight.

Moose get problems with sun crusted snow in late March, when the sun melts the snow on the top during sunshine hours, while it freezes in the nights again to a hard surface. On such snow moose cannot run away or defend themselves. They try to stay in low level snow during that period (e.g.in the forest, where also the sun cannot melt the surface or on frozen lakes). 
In late winter the food supplies decrease and moose get more solitary - in that time they have less possibility to defend in a croud and get more aggressive therefore. They also seek streets and rails, where the snow is low - with a high risk on the other side to suffer from m ore technical threats.

Human prey

Of course - as in so many cases - the main threat for moose is the human being. Therefore this topic has an own section - please check "Moose & Human"

Winter time makes everything more complicated ...

The winter time in typical moose habitat brings quite low temperatures, lots of snow and little food they have sometimes to dig for. For all these problems moose are usually well suited: 
He builds up stocks for the winter time by eating enormous amounts when food supply is generous 
He has a thick winter coat with hollow hair to keep warm 
He has long legs to walk through snow up to 1 meter. 
He keeps together with other moose to build moose yards
He uses as little energy as possible by as little action as possible during that time.
He tries to find areas with less snow for better food supply and better defense possibilities

Anyhow only the strongest survive. In winter time up to 80% of the summertime food supply has vanished - moose who haven't stored enough reserves during summer and autumn easily run out of energy Those choosing streets and rails for lower snow often are killed - e.g. several hundreds of them by trains just in British Columbia each year. They get weak due to missing nutrition and minerals and by that get easier prey for wolves - also if they are in deeper snow and cannot escape or defned themselves.

Deseases and parasites

Another risk for moose to survive is a really small thing: The winter ticks (Dermacentor albipictus) biting the moose. This is a high risk especially in very cold and hard winters, as the moose's skin, so important to keep the body warm in low temperatures, is damaged - mainly because the bites are itching so much and the moose do anything to stop this. So they scratch off parts of their protecting coat, and if the winter is hard and enough winter ticks are attacking the moose, it can get critical because of hypothermia. The ticks proliferate enormously on moose until he nearly hasn't left any coat - in this case he get's called "ghost moose".
One source mentions, that up to 50% of the moose population can be eliminated by such small attackers. The winter ticks, occuring generally seasonally in the time from late autumn until early spring, can get a real pest in some years, with extremely high volumes. One moose may "accomodate" up to several ten thousands of these parasites.

Also a common risk is the co-existence of moose and white-tailed deer (Odocoileus virginianus), a close relative to moose,  in North America. A fatal illness, known as moose disease, is common in these areas. Blindness, paralysis and disorientation are typical symptoms, very often leading to death. 
The brain or meningeal worm (Parelaphostrongylus tenuis), located in infected white-tailed deer's brains, does usually not harm the animal, as it seems to be adapted to the worms. 
In the white-tailed deer the worms lay eggs, which occasionally wander in the blood to the lungs, where they get larvae. From there they can get further up until they can be swallowed, finally ending up in the deer's droppings.
Now snails or slugs, "trying" the droppings, take over the larvae. Occasionally those "infected" snails or slugs are eaten incidentally by a moose together with leaves they might sit on. Of course the moose can also directly be infected from the deer's droppings when eating.
The larvae now leave the snails in the moose's stomach and might reach the spinal tract from there, which they follow in direction to the brain - badly damaging the moose's nerval system and leading to the disease, which normally is lethal.
Moose and white-tailed deer come closer together in recent times, mainly due to human deforestation creating new habitat for the species (mainly white-tailed deer expanding northward) and leading to an expansion of the problem.

The last parasite endangering a moose's life in winter time is the giant liver fluke. This parasite needs canine as alternate host and causes liver damage.

Also mentioned, but not dangerous, is a moose-specialist beyond the insects: The Moose fly (Haernatobosca alces), which seems only to like moose blood and seldomly leaves it's host unattended ...

Damage caused by moose

The damage to young forest as preferred diet, expecially if too many moose are in a particular area, is one of the problems the species gets on his account.

As intelligent animals, who moose are, they easily adapt their diet to farming goods such as oats as well. Farmers are partly  compensated for the caused damage in Sweden, and electrical fences shall protect agriculture. But it can be understood, that damages like the mentioned don't contribute to a positive attitude towards moose, and so moose are more seen as pest in countries like Sweden. Additionally traffic accidents with moose are quite common, and due to the big height and huge mass of the animals a high risk for life is not only on the moose's side.

By the way: Now that the population of bears and wolves grows again, hunters start complaining, that not enough moose might be left for hunting ... what a crazy world ...