Rhinos in zoos - horn length and shape

J

Jurek7

Well-Known Member
15+ year member
I think it was discussed before, but recently I was impressed again by horns of some wild rhinos. Not only much longer than in zoos, but also different shape - narrow and pointed. Zoo rhinos have more like thick stumps.

https://lh4.googleusercontent.com/p...8JUS6Si_4AH3vrHXV94MwUTaqW-9gsBPXnoD1Np-w6b1B

Given that zoos are after making their exhibits impressive, why don't they care about rhino horns?

I had an idea that different horn shape can be related to wild rhinos wearing their horns on softer materials (shrubs and grasses vs. walls and metal). In this case, zoos might quite easily provide rhinos bunches of branches or similar to wear their horns.

Interestingly, which rhino in human care has the longest horn?
 
Jurek7 said:
I think it was discussed before, but recently I was impressed again by horns of some wild rhinos. Not only much longer than in zoos, but also different shape - narrow and pointed. Zoo rhinos have more like thick stumps.

https://lh4.googleusercontent.com/p...8JUS6Si_4AH3vrHXV94MwUTaqW-9gsBPXnoD1Np-w6b1B

Given that zoos are after making their exhibits impressive, why don't they care about rhino horns?

I had an idea that different horn shape can be related to wild rhinos wearing their horns on softer materials (shrubs and grasses vs. walls and metal). In this case, zoos might quite easily provide rhinos bunches of branches or similar to wear their horns.

Interestingly, which rhino in human care has the longest horn?
Click to expand...
Zoos definitely give their rhinos branches. Escpecially black and Indian rhinos that need it in their diets. From my observations, the rhinos just choose to use the harder objects to wear their horns. I don't think that zoos don't care about the horns of rhinos, just that you can't change that behavior or the choices the rhinos make when it comes to wearing their horns down. And if they can change that behavior, it is not harmful to the rhinos to have short horns so why put in the effort when you could be spending it on actual husbandry training that is beneficial to the animal.
 
My observations are the same as Echobeast. The rhinos are using harder materials to sharpen their horns, which gives more wear. Since rhinos need strong containment, removing such substances from most exhibits isn't feasible. A study comparing horn sharpening and horn growth between captive and wild rhinos would be very interesting.

Curious, have any zoos removed their rhino's horns due to concerns of poaching? I can't recall ever hearing of such a scenario but knowing the horn's value on the black market it could happen I suppose...
 
Great Argus said:
My observations are the same as Echobeast. The rhinos are using harder materials to sharpen their horns, which gives more wear. Since rhinos need strong containment, removing such substances from most exhibits isn't feasible. A study comparing horn sharpening and horn growth between captive and wild rhinos would be very interesting.

Curious, have any zoos removed their rhino's horns due to concerns of poaching? I can't recall ever hearing of such a scenario but knowing the horn's value on the black market it could happen I suppose...
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Pretty sure there is case of zoos removing the horns on rhinos. There are a few zoos with 24hr security but more so to protect all its animals than just for those wanting to steal a rhino horn.

Also imagine it would take time to steal one, as you got to imobilise the animal somehow (drugs or killing it) before you could attempt to remove it. Much easier in the wild when you are unlikely to have anyone for miles around. Although finding animals may be tricky.

Also heard of zoos taking the tip off the animal to avoid animals hurting each other.
 
taun said:
Pretty sure there is case of zoos removing the horns on rhinos. There are a few zoos with 24hr security but more so to protect all its animals than just for those wanting to steal a rhino horn.

Also imagine it would take time to steal one, as you got to imobilise the animal somehow (drugs or killing it) before you could attempt to remove it. Much easier in the wild when you are unlikely to have anyone for miles around. Although finding animals may be tricky.

Also heard of zoos taking the tip off the animal to avoid animals hurting each other.
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At Thoiry in France, a rhino was killed for its horn in 2017. There's a thread here, with some comments regarding other zoos (e.g. Pairi Daiza and Dvur Kralove announcing they would be removing the horns from their rhinos as a safeguard).
Rhino killed [Thoiry Animal Park]
 
Echobeast said:
Zoos definitely give their rhinos branches. Escpecially black and Indian rhinos that need it in their diets.
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I think branches laid down to eat are not convenient for wearing horns.

It is possible that a rhino can be persuaded to use soft toys, if they are more pleasant than hard surfaces. I thought about some soft, disposable hanging toys, for example bunches of dead branches, or maybe a sack filled with something and sprayed with some scent which rhinos like. I know that an Indian rhino in Warsaw often got heavy leather medicinal balls to play with.
 
Does anyone know if climate plays a role? Some antelope kept in cold areas wind up with poorly formed horns (though I realize that antelope horns are bone sheathed in keratin rather than all keratin like a rhino horn). The rhinos at the San Diego Zoo Safari Park seem to have nicely formed horns. I don't know if it is because they are rarely in small enclosures rubbing on concrete or steel or if it is because the weather is usually warm.
 
Jurek7 said:
I think branches laid down to eat are not convenient for wearing horns.
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Jurek7 said:
I thought about some soft, disposable hanging toys, for example bunches of dead branches, or maybe a sack filled with something and sprayed with some scent which rhinos like.
Click to expand...
Zoos definitely don't just lay branches on the ground. Some of the simplest enrichment is changing the placement of everyday objects like food. Hanging browse is pretty simple and pretty much every keeper does it.

I do know that rhino horn softens when wet and the rhinos I know love to rub their horns after it rains so potentially rhinos in wet climates generally have shorter horns because they wear easier. Again, I don't think this is unhealthy or bad for the rhinos to have short horns in zoos.
 
It's a little different story, a male white rhino named Kodol-i(코돌이), who died in an accident on August 5, 2012 while breeding since the Seoul Zoo opened in 1984, had its front horns split into three pieces, as if they had split to the roots.

R800x0

Photo of Kodol-i's horns.
Image source is here.​

The Seoul Zoo's zookeepers and internet news said Seoul Zoo trained around 2007 to learn each other's faces to re-mix the long-separated female white rhinos and Kodol-i, but in that training, Kodol-i was too rubbing his horns on walls and pipes. So his front horn was broken into pieces, and the horn did not return normally until he died.
​
Since they were enshrined with the females, Kodol-i was said to have been driven away by the females due to their lack of normal horns. I think this Kodol-i's story is the reason why zoos should provide rhinoceros with something soft to rub their horns.
 
The shape of a rhino's horn is absolutely a result of rubbing as outlined above. If a rhino did not pare its horn into shape then it would be an amorphous lump. Hard surfaces are better for wearing down horn so are naturally favoured by rhinos. The availability of such hard objects is restricted in the natural environment hence why they use trees and shrubs (yes, I know rocks and boulders exist but are certainly not as frequently encountered as softer objects in most rhino's natural habitat). The purpose of the rubbing is multi functional and in some species at least rubbing trees and twisting vegetation with the horn is a territorial behaviour.

In zoos the natural horn rubbing can also evolve into a repetitive behaviour. Combined with typical containment methods this leads to abnormal horn shapes. This in itself is not, in most cases, a welfare issue - though the display of repetitive behaviour should certainly be examined and addressed if possible. The problem comes if a horn splits down to the root and exposes more sensitive tissues beneath - leading to infection.

Historically the design of rhino containment has consisted of horizontal or vertical bars, cables, walls or a combination of these. The African rhinos typically sway their head from side to side when horn rubbing. When done on horizontal bars or cables, this results in horizontal grooves or splits. The Asian rhinos tend to rub the horn up and down hence why Indian rhinos often rub the horn completely away - particularly if housed within solid walls.

There is a movement nowadays to keep rhinos behind diagional bars - especially internal quarters (like has been done with elephants for some time now) - to try to reduce horn damage

If a zoo could contain its rhinos primarily with hotwire and provide suitable rubbing surfaces then I am certain that horn shape in zoos should improve. This wouldn't necessarily remove the likelihood of excessive or repetitive horn rubbing which would have to be reduced via environmental enrichment.

A couple of other factor to keep in mind: 1) Nutrition. The diet of rhinos in zoos will not exactly replicate that of those in the wild and an excess of, for instance, protein (e.g. the use of lucerne for grazing species), might well cause overgrowth of horn material. This could certainly contribute to poorly formed horns. 2) Humidity. If rhino horn becomes too dry it can split. 3) Unnatural social grouping. Amongst bachelor groups (of which there is an increasing number in European zoos - particularly whites) there is likely to be an unusually high level of aggressive behaviour between individuals which results in horn damage.
 
@Paradoxurus this is the issue though with captive aminals..zoos tend to protect large shurbs/trees from Rhinos because of the damage they cause often leading to the death of the trees. Would dead wood provide the same to living wood? Not sure but cannot think best why to descirbe why it would not.

I think it was Howletts have a black rhino that often had a green horn from rubbing on the fencing. Pretty sure they had a notch from the rubbing.

Thanks for the information esp Indian Rhinps more like to rub up and down.
 
Jurek7 said:
Interestingly, which rhino in human care has the longest horn?
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I’d say some of the Southern white rhinoceros cows at Werribee Open Range Zoo would up there, especially Sisi and Letaba:

WERRIBEE ZOO: Buffet for the beasts - Star Weekly

Sisi gave birth to three calves between 2002 and 2011, all of which were killed by her. The calf born in 2011 died of internal injuries, including a ruptured bowel. Staff believe this was caused by Sisi’s horn.

The strangest horns I’ve seen on a rhino are on Mapenzi at Orana Wildlife Park (again a Southern white rhinoceros). They curve downwards towards the ground:

Stock Photo - White Rhino at Orana Wildlife Park, Christchurch, New Zealand
 
Zoo rhinos usually have nice, thick base of the horn. So the keratin production is fine, the problem is how a rhino scratches and wears its horn. It would be interesting to see what movements and what material is used by different rhinos in the wild and in zoos. This probably would fairly simply explain the horn shape.

Zoofan15 said:
I’d say some of the Southern white rhinoceros cows at Werribee Open Range Zoo would up there, especially Sisi and Letaba:
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Interesting, This horn shape - long and thin - is actually most similar to one of wild rhinos. I can only guess that in Werribee rhinos are probably outdoors all the time, with similar opportunity to shape the horn.

Zoofan15 said:
The strangest horns I’ve seen on a rhino are on Mapenzi at Orana Wildlife Park (again a Southern white rhinoceros). They curve downwards towards the ground
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It is found in some rhinos in Europe, too. Among others one of the last Northern White rhinos in Dvur Kralove had such horns. Don't remember seeing it in the wild. One can guess that the rhino might e.g. have a beam so positioned that it rubs the front horn from backwards - resulting in the horn curving forwards.

I also saw photos of at least one wild and one zoo black rhino with three horns - not split, but an separate one well higher up the skull.
 
Jurek7 said:
So the keratin production is fine, the problem is how a rhino scratches and wears its horn. It would be interesting to see what movements and what material is used by different rhinos in the wild and in zoos. This probably would fairly simply explain the horn shape.



Interesting, This horn shape - long and thin - is actually most similar to one of wild rhinos. I can only guess that in Werribee rhinos are probably outdoors all the time, with similar opportunity to shape the horn.
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Yes, afak, its all related as to how the rhino wears the horn down. I believe in wild savanah-living rhinos, either moving through grass and/or rubbing/polishing on e.g. termite mounds or growing wood may create the typical long, pointed and smooth/rounded appearance of the horns. In the forest-dwelling Javan and Sumatrans, movement through jungle foliage may serve a similar purpose. Both these species have typically very small pointed horns in the wild, usually no more than just a little rounded spike. Torgamba, the captive Sumatran at Port Lympne grew very long thick horns, like many black/white captive rhinos, and old photos of Sumatrans at London Zoo in the past show exactly the same type of horn development. Presumably whatever causes them to wear down in the wild was not present in these captive situations.

I think in captivity that is the overall cause of the growth of the thicker horns usually seen. Wear from stereotyped rubbing seems most common in Indian rhino.

I'd like to know what rubbing surface these Werribee rhino have to use as their horns are far more similar to wild rhino than usual.
 
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Luckily, there was no theft of rhino horn from a zoo or a museum in Europe in the recent years.

Pertinax said:
I believe in wild savanah-living rhinos, either moving through grass and/or rubbing/polishing on e.g. termite mounds or growing wood may create the typical long, pointed and smooth/rounded appearance of the horns.
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I am now purely speculating and may be completely wrong. In a zoo a rhino rubs its horn against a wall or a thick surface. The whole pressure goes to the tip and front of the horn. There is little possibility to access the back surface of the horn. The result - the horn becomes blunt, short and lump-shaped.

In a bushy or grassy environment, the rhino rubs its horn against tall grasses or thin bushes. The thin, curving vegetation accesses all surfaces of the horn. There is little resistance to the tip. The horn becomes narrow and very long. So a zoo giving rhinos clumps of branches hanging or mounted in a stand, can shape the rhino horn a different way.
 
Jurek7 said:
Luckily, there was no theft of rhino horn from a zoo or a museum in Europe in the recent years.



I am now purely speculating and may be completely wrong. In a zoo a rhino rubs its horn against a wall or a thick surface. The whole pressure goes to the tip and front of the horn. There is little possibility to access the back surface of the horn. The result - the horn becomes blunt, short and lump-shaped.

In a bushy or grassy environment, the rhino rubs its horn against tall grasses or thin bushes. The thin, curving vegetation accesses all surfaces of the horn. There is little resistance to the tip. The horn becomes narrow and very long. So a zoo giving rhinos clumps of branches hanging or mounted in a stand, can shape the rhino horn a different way.
Click to expand...

Yes, I think you are working on the correct lines there. Captive rhino horns are usually 'block shaped' rather than smooth and rounded as in the wild.
 
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