Stone/Dall vs. Rocky/Desert Bighorn Sheep

[RenoHunter]

I just posted this in the general hunting forum before realizing there was a sheep forum. Does anyone know why stone and Dall sheep tend not to broom their horns as much as rocky and desert bighorn sheep? Is it because stone and Dall sheep typically don't carry much mass at the tips and this doesn't affect visibility as much?

 

[Zeke]

Interesting topic, Reno.

Like LBH said in the "general" section, there are several theories as to why the big horns broom more than the thin horns.

A couple "usual" answers are blocked vision and aggression. (probably the most popular and reasonable)

I've also read that it's related to the environment: dry v wet, rocky v grassy, etc.

I've even read where some sheep dig for food with their horns or brooming is all about the way they rest their heads. (I took a few of those with a grain of salt)

Some sheep broom while others in the same herd don't so much. So, I certainly cannot come up with a definitive answer for you and I'm not sure one exists.

Broken horns is often related to disease but that's totally different than brooming by a healthy ram.

Maybe it's like some kids bite their finger nails while others don't.

I'm sure some of the other (better) sheep guys will weigh in on the discussion.

Zeke

 

[littlebighorn]

Reno,
Your excellent question got me digging through my old pal, Jack O'Connor's book "Sheep and Sheep Hunting". He postulates that, while we don't know for sure all the reasons sheep broom their horns, the main theory seems to be that longer horns can block a ram's vision from predators, so they broom them in order to see better. Crusty old Jack also notes that some shapes of horns are more likely to be broomed than others. Close to the face shapes that then flare seem less likely to be broomed than tight flared horns that come up in front of the eye.
One point the old professor makes about the difference between Bighorns and Thinhorns is the timing of their arrival in North America. Most researchers suggest that all North American sheep came from Asia across the Bering land bridge and down on our continent.
The Desert and Rocky bighorns migrated from Asia long before the Stones and Dalls. They established here and then the much later arriving "thin horns" came and found the wet northern country to their liking. But he notes that the thin horns look much more like the longer less likely to broom Asian sheep (perhaps more closely related).
That may be more than you want to know, but I enjoyed the research! Probably lots of other theories as well.

 

[RenoHunter]

Not at all. Every time I see different sheep that question comes to mind. Thanks for looking into it, that is very interesting. I wonder if the types of forage consumed could potentially make thinhorns have stronger horns and thus be less susceptible to brooming? Due to the larger body size of ungulates and the greater densities it seems to me that the northern part of our continent would have higher quality forage due to the wetter climate. But this brings up the question of why did the bighorns pass by this area on their way south? Possible the climate was too harsh at that time. You said the research suggests that thinhorns arrived much later than bighorns, do you happen to know what the estimated time lapse between bighorns and thinhorns populating the continent is? I think learning about the history of our wildlife is of utmost importance to understanding some of the issues that plague them today. I assumed that there was an answer to that question but it sounds like nobody is 100% sure why sheep broom their horns in the first place.

 

[BuzzH]

I think the reasons given are all valid...but I also think some of it is just habit.

Check out the smooth, polished portion on the horn of the desert ram I shot in AZ.

That ram just had a habit of rubbing the top of his horn for some reason. I suspect brooming can also be the result.

I notice when I watch rams, they quite frequently just rub their horns on rocks, trees, brush, etc. for no real apparent reason.

 

[greatwestern]

I as well think its a great question, and I remembered we talked about it a few years ago on here, so I poked around and found the thread in the archives:

http://www.monstermuleys.info/cgi-b...880&forum=DCForumID8&archive=yes#.UxDRGGePK1s

Certainly not conclusive by any means, but a lot of good ideas and observations discussed

Anyway, its a very interesting subject!

Cheers

 

[Zeke]

LAST EDITED ON Feb-28-14 AT 11:31AM (MST)[p]Again, nice ram Buzz!

I agree, I think it's tied a bit to habit too. I've seen sheep rub on everything just to rub, I guess. This seems to be a more common practice with bighorns (or I've simply spent more time among them).

The only poster who might have actually been here to witness the original influx of wild sheep into NA would be littlebighorn!!! LOL

Zeke

PS; that's a great thread GW. I'm glad you refreshed our memory with posting the link. It's always fun to see others ideas.

 

[RenoHunter]

Beautiful ram BuzzH. I browsed through the older forum, I found the idea that sun and lack of moisture can cause some horns to crack more easily pretty interesting.

 

[littlebighorn]

LAST EDITED ON Feb-28-14 AT 05:04PM (MST)[p]There you go again Zeke. Sweeping my cane right out from under me!
Keeping MY AGE in mind, I recall one Russian researcher claimed that well after the Bighorns moved south across the ice to warmer climates, the thin horns got hung up further North until the continental ice melted and left the wet lush vegetation in Canada and Alaska. Since that suited their needs they stayed there rather than continuing south like the Bighorns.
He also suggests that their horns(and perhaps behavior) are more like the Asian sheep. So vegetation, habits, genetics, etc. etc. could all come into play.

I didn't actually witness this event because I was having too much fun riding my hairy mammoth and chasing Sabor Tooth Tigers with my 300 short mag spear!!!

 

[uphill]

Might as well throw in my two cents on everything from ice ages to horn tips. The following is just general discussion. There are exceptions to every rule and in nature there are very few rules but an infinite array of variables.
I believe Bighorns crossed from Asia into North America well ahead of Thinhorns. Along comes a serious ice age and the ice caps at the poles begin to grow and spread towards the equator. The North Pole ice cap advanced southward and any species that wanted to survive better stay ahead of it and the Bighorns did. So the Bighorn is effectively pushed out of northern Canada by advancing ice. At this point the Bighorn is one species. I respect that there are differences between desert and rocky mountain bighorns just as there are differences between Texas whitetails and Nebraska whitetails...but they're all pretty much the same sheep/deer.
Now a lot of time passes, the ice age has receded and the Bighorn is expanding its range southward (desert) and back to the north (Rocky) from hence it came. A brand new animal enters North America from Asia, the Thinhorn. Not Dalls and Stones, just the ancestors of the Dalls. The Thinhorns make their new homes in the far north of North America and when a few of them go south for spring break they get drunk and hook up with some Bighorns. Six or seven months later the first Stone sheep is born. Thinhorns and Bighorns are related but they did a great deal of evolving separated by the Pacific Ocean and they are very different. Just as blacktails and whitetails are different. Don't believe me? Expose a Bighorn and a Thinhorn to pneumonia. The Bighorn dies and the Thinhorn doesn't so much as catch the sniffles. I believe this genetic difference has more influence on brooming than fighting, humidity, feed, habits etc.

Humidity: Sheep horns are made of proteins very similar to your own hair and finger nails which as you know can be affected by humidity. Problem with that theory is that sheep habitat all across North America is pretty damn dry. Alaska might seem rainy but for eight months a year its just cold and dry.

"High quality feed in the north": While the north country can be lush in summer the trade off is suffering through longer winters. Problem with that theory; If the feed in the north is so superior leading to stronger horns that don't broom, why are there so many bighorns in the south that can grow over 180 inches of horn and very, very few Thinhorns have ever been able to do that?

Add up all the time a bighorn spends fighting, rubbing, and resting on his horn tips...that adds up to a fairly miniscule portion of his life. The real wear and tear is done during feeding. Hour after hour, day after day, month after month. That is where the real "daily grind" takes place. From birth to about 5/8ths curl the horn tips are fairly safe because while the ram is feeding they point up and away from the rocks. From 5/8ths to 7/8ths the horn tips are in jeopardy because they constantly hit rocks as the ram is trying to get food in his face. If the bighorn approaches full curl the wear and tear slows because the tips are no longer pointed into the rocks as he feeds.

In some areas Bighorns broom heavily and rarely get past 3/4 curl because the genetics and nutrition are such that the ram reaches a certain age, the horn growth rate slows and the horn base can't push out enough new horn material to overtake the daily grind. The horn ends never get pushed past 7/8ths where they are a little safer from the daily grind. In some areas of the desert the food is rarely taller than a few inches and the bighorns are constantly grinding down their horn tips and you're lucky to see a legitimate 3/4 curl.. While in other areas the bighorns practically browse off of waist high bushes and their horns tend to be longer with less brooming.

In my opinion brooming to preserve vision is a myth. By that rational genetic selection would have seen long horn rams eaten and we would be left with a species of half curls. By the same rationale caribou should snap off their shovels and drop tine's would be broken off along with the velvet. Ever see a picture of a beautiful full curl bighorn with some brooming. Then you see a picture of the same ram a year later and a year later. He's so old his horns are hardly growing and yet he doesn't broom them down any shorter than in the first photo. Why not? The horns are obviously in his vision and he knows how to broom them. They don't get shorter because they have grown to a point where they are safe from the daily grind of feeding. That's how they got some brooming in the first place.

So why do bighorns broom and dalls not so much? Because just as they are similar but different animals their horns look similar but grow differently. First we need to understand that ram horns don't grow evenly all along the circumference of the base. If they did they would grow straighter like an oryx or a mountain goat. The portion of the horn base emanating from the rams forehead (outside edge) grows faster than the rest of the base and that along with other factors forces the horn into a curl. If the outside edge grows a lot faster than the inside you will have a very tight curl. If the bases grow slower in the area above the eye and faster atop the center of the skull the bottom of the curl will get pushed inward into what is commonly referred to as "argali type". Second, we can't understand this by looking at the eight plus year old sheep mounted on the wall. By then the brooming is done and the differences in growth patterns are less pronounced. Look at two to three year old rams.

Look at an average thinhorn ram when he is a little half curl. That half curl is likely to approach a true 180 degree arc and if you traced that arc onto a piece of paper and continued its trajectory you would draw a circle of a given diameter. When that thinhorn ram reaches three quarter curl his horn tip is going to be turned ever so slightly upward and somewhat protected from the rocks. Furthermore, as that ram's horn grows towards 7/8ths his horn tip will be set back from the corner of the mouth affording it a little more protection. In short, from day one the thinhorn ram grows a nice round curl that keeps his horn tip back away from the rocks in front of his mouth.

Now look at a half curl bighorn. The term half curl is somewhat inappropriate because its unlikely the ram's horn will be 180 degrees...120 degrees is probably more like it. Now trace the arc of that young bighorn ram's horn and continue its trajectory until you come full circle. The diameter of the circle is A LOT bigger than that of the thinhorn ram. As he matures the bighorn ram will compensate for this and the outside edge of his horn will grow faster and his horns will form a nice curl. But it's too late for the tips of his horns, they are straight out there in harms way. As he rounds 5/8ths curls his horn tips are sticking down and farther forward than the thinhorns did. Hello rocks, goodbye lamb tips. This growth pattern is most pronounced in "California Bighorn" sheep and coupled with their wide flaring horns, they are doomed to broom.

 

[greatwestern]

LAST EDITED ON Mar-01-14 AT 11:00PM (MST)[p]Very interesting speculations Uphill...I agree that the bighorn represent a much earlier colonization by wild sheep of this continent, and that there might be some subsequent intergrade between them and the Dall's that have resulted in the Stone's...geographically it certainly makes sense. The so called Fannin makes a strong case for such an idea, further north between the the primary ranges of the white and black "thinhorns"...Also, it is very probable that there was some 'retracing of steps' made by the NA colonists back across Beringea that have influenced at least some of the Snow's of extreme North Eastern Asia (consider the pelage of the Kamchatka sheep in favorable comparison to our own bighorn, headgear notwithstanding)

That opined, I do not agree that primary brooming is attained through general feeding...no, not at all...maybe a bit of "polishing" of the broom, yes (such as breaking open barrels, or using a horn's terminus to probe a mineral lick, etc). I've yet to witness a mature ram of whatever horn conformation that had to fight with his own horns to get a bite to eat, rocks or no rocks

Also strongly disagree with the idea that wider, "flaring" horns are more susceptible to breakage/brooming...my observations reflect exactly the opposite in fact. I think that the wider set a rams horns are, the less likely the chance of destructive contact between the tips during clashes...the closer the curl, the greater the potential for damage from such contact under impact

I do agree that that the idea of rams brooming down their horns as an anti predation measure is an old myth...I just can't give the sheep (however savvy otherwise) that much cognizant credit

Will dig around and post up some photos tomorrow when I have a bit more time

Anyway, like I said, always an interesting subject!

Cheers

Adam

**edited for typos

 

[Zeke]

I've seen lots of split, cracked and frayed horn tips. Feeding may "polish" this off but "fighting and general butting" did the initial damage. We've all seen the splits and chips happen... Or at least the day after it happens.

We might have to pass to the other side and ask our Maker! He'll have the final word. I suspect we'll find it's a combination of several factors.

Cool stuff, great thread. Anything's good that keeps up thinking about wild sheep!

Zeke

 

[Trammer]

LAST EDITED ON Mar-04-14 AT 01:05PM (MST)[p]In addition to the many great factors already mentioned I think you should also consider why evolution may favor the presence of horn tips in Thinhorns as well as removal of horn tips in Bighorns. I suspect that due to more wolf or grizzly bear predation on sheep in the North, horn tips may actually be an asset to a ram and for example, serve as some type of a weapon for a ram to slash away at wolves.Also the horns of thinhorns weigh much less than bighorns and as a % of body weight even less.
One reason natural selection may favor horn brooming in bighorns may be that horn tips for them are essentially funtionless,and are a liability due to extra weight and they are the most extra weight and therefore more of a liability for the the sheep that tend to broom the most. Imagine the poor Scrivens ram. (the 205 point world record Desert Sheep) A 140 pound animal packing around 30 pounds of horn on his head for a total body weight of 170 pounds. Its no wonder they would want to lighten the load.
Remember, wild sheep are protoplasmic vessels for their genome and the genome is continuously redesigning and reprogramming the vessels for efficiency.

GrandSlam #911

 

[littlebighorn]

This is a fascinating and heady idea exchange. There's certainly plenty of great sheep experience and thought coming from this group. It no doubt represents lots of campfire discussions and hardy reading sessions about these interesting creatures we love to pursue. Great topic for sure!

 

[greatwestern]

LAST EDITED ON Mar-03-14 AT 11:00PM (MST)[p]Man, going through this crappy back up drive of thousands of untitled pics has got me about crosseyed X)

Anyway, here are a few for now...talk about an overnight brooming surprise Zeke, ol Rambo here got his left horn busted up between last light before the opener and the next dawn when the season commenced. After running the show in the days previous, he'd by then peeled off from all the hustle and bustle and was by himself. As well as the horn damage, he appeared pretty damn tired and sore as well, staying mostly bedded until we killed him around mid day...the rest of the sheep were as frivolous as ever. I don't think he'd necessarily got his ass kicked, despite the battle scars, just think he'd finally "got 'er done" so to speak

Before (black ram in center):

After (figured he knocked a good inch or so off, plus the big chip):

Here he is getting sucker popped by a punk immediately after running off two mature dudes:

oh and here he is feeding (in the rocks! with his primary rival between bouts

Will post up some other pics for illustrative purposes when I get a chance, had about as much computer as I can stand for now

Cheers all

Adam

 

[Zeke]

Old Rambo shows the classic example of "Grand canyon erosion".

Yes, there is everyday erosion which polishes the rough rocks but it's the cataclysmic events that do the most damage.

My thoughts are that horm brooming is about the same thing. The everyday activities polish the horn but it's the big "Rambo" events that really broom off the horns.

Thanks for the additional pics GW. KEEP DIGGGING, we love them!

Zeke