Fall is time for the annual moose rut

Moose
Moose

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 Chel Anderson is a botanist and plant ecologist for the Minnesota Department of Natural Resources. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel.

 
Anderson: Hi, Jay.
 
Well, everybody’s favorite very large animal: moose. Chel, what’s this about the rut?
 
Anderson: Oh, the rut. Yeah, I think the moose rut is a pretty interesting phenomenon that we’re lucky enough to have some sometimes up-close and personal experiences with aspects of, and, boy, that’s not something to take fort granted this mating season, which is what the rut refers to in the case of moose. Of course, moose have been, in a way, the mature moose that are going to be doing the breeding, which is mostly not most of the population. Most of the population of moose are juveniles and calves, and those members of the population aren’t going to be doing the breeding, it’s going to be a much smaller group of animals that are the mature bulls and the cows. The most productive cows are in the range of four to twelve years old, and then the bulls, the mature bulls that will do most of the breeding, are between five and ten years old, so it’s a small part, really, of the total population that do all the breeding. In the world of the moose, bulls really prepare all summer in a sense for the breeding season, because they’re growing their antlers, and it’s high levels of testosterone in their bodies that help them harden off those antlers and get them all spruced up for this particular period of the year that we’re in now. Females, of course, have been striving all their lives and now over the summer to be in good condition and be ready to be in good shape for the breeding season. In the moose range is a wide variety of conditions, right, we have moose that live in the tundra; we also have moose like here that are living in the forest. Well, because of that wide range of environments that moose live in, they really have two different strategies that they use for breeding depending upon where they live. We’ll focus on the one here in the forest, but just a short note on those that live in the open, they use more of a group breeding strategy. So, moose, bull moose, round up kind of a loosely-formed harem. But, of course, if you’re in the forest, things are pretty different in terms of how do you find each other, because you can’t see other moose across vast distances. So, here moose typically are just breeding in pairs. Now, you may have a bull that’s breeding a number of cows, but they’re not keeping them together in a group. They are focusing their attention on finding individual cows and being with them when they’re ready to mate and then moving on to another cow.
 
My experience has often been that the cows, you’ll often hear them bellowing and then the bulls bellow back. Sometimes it’s quite a distance, so I’m assuming that they finally get together.
 
Anderson: Yes, indeed. They use both visual cues and auditory cues and olfactory cues, so smells and sounds are both important. Cows give a low, kind of wavering moan. The bulls tend to do something that’s more of a grunt, so those calls can help individuals find each other. They also help the males know where each other are, and they also use smells. So, cows that are breeding age, they’ll be stripping trees of their bark. They don’t eat the bark, they just peel it away, strip it away, and then they rub their heads all over that stripped wood. There are a bunch of glands on their head and they leave their scent there. So, this is something that a bull can pick up on and they can kind of check out that female before he’s actually seen her in person. Both the male and female urine have smells in it, so those clues are being left and assessed regularly by both males and females. Then, the mature males, they really focus on breeding at this time, and they actually give up eating to really just concentrate on finding cows and mating with cows when they’re ready. A bull’s antlers are primarily for the purpose of displaying their superiority to their competitors, but also for displaying their superior qualities as a mate to a cow.
 
They don’t fight that much?
 
Anderson: Sparring is a very dangerous thing and about the only time it will happen is when two bulls think they have the larger of the racks, then that’s when a sparring match of some kind is likely to occur. As I said, it’s a dangerous thing, puncture wounds are not uncommon, and occasionally bulls lock antlers and they can’t get free. That will lead to the death of both animals. Think about even though the tines on a moose antler may not come to as sharp of a point as some other species do, think about the force that a moose can put behind it’s antlers. It’s probably more than we can really imagine. We probably all come across, if we’ve spent much time in the woods, places where you can see a moose has done a lot of rubbing of its antlers. And once moose have shed the velvet, and they’re all shined up and all hardened up and ready and into the mating season, then they’ll use that rubbing and that clacking and thrashing against trees and shrubs as a way to broadcast their superiority, because the bigger the antler, the bigger those palms, that makes a very hollow sound that can go a long distance, so they can use that to assess the competitors’ locations and their size. And, once they’ve actually copulated, it doesn’t go on necessarily for very long, and then, once it’s over, they pretty much go their separate ways. And, for the males, of course, once they’ve finished breeding all the cows that they’ve been able to connect with, they go off to spend the winter or the next couple months trying to regain the weight that they’ve lost and get ready to survive the winter. The females, of course, they’re now going to be carrying an embryo and a little moose through the whole winter, so they need to go off and stay really fit and healthy to bring that moose into the world in the spring. So, once the rut is over, they go their separate ways and they don’t really meet up again until next fall.
 
Chel Anderson, DNR botanist and plant ecologist. Thanks for helping us understand what’s going on around us with moose this fall.
Anderson: You’re welcome.

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