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 Post subject: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Thu Jul 15, 2010 8:43 pm 
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I Thought some mites might find this as interesting as I did :) Its some of the research the School of Animal plant and environmental sciences at WITS has done on the subject and how the scientists went about trying to figure out the problem.

Sable and Roan antelope are both members of the Bovidae Family and the Hippotragini tribe. They are also members of the same genus Hippotragus; where sable in SA are H.niger niger and roan are H. equinus.

The problem: During the late 1980's and particularly after 1991 there was a sharp decline in the population of both antelope in KNP. In general there is a list of causes that are generally responsible for the decline in a species:

1:Climatic extremes such as drought
2:Habitat degradation
3:Competition from other species
4:predation
5:Management interventions
6:changing ecosystem context

So is the decline in kruger caused by an external factor like climatic and habitat change or due to internal management plans? The scientists decided that the best way to try and understand the problem within KNP was to study the dynamics of how a successful breeding population of sable functions and to do this they looked at the herds within a reserve in the Waterberg where there are also no predators. The initial objectives where to look at the time of year that they are the most vulnerable as well as the resources they rely on to support them during these critical periods.

Objectives:
1: large scale- Habitat usage
2: small scale- species of plants foraged
3: behavioural ecology
4: The faeces were also examined (nitrogen and phosphorous as an indicator of quality)

Females from each herd were collared as they form the herds while adult males of about 2-3 years form bachelor herds.

Some of the basic observations:
1: behaviour of each animal within the herd taken at ten minute intervals
2: proportion of daily time spent foraging
3:bites, steps and time in between
4: quadrats ( usually 1x1m squares placed over the surface as a representative measure) to determine grass species and length of the grass eaten.

The study was running during periods where the reserve was burnt and all the herds would feed extensively in these burnt areas on the new green shoots which contradicts with what was previously known about the animals. So after a few years the results of the study suggest that sable are able to adapt their behaviour in terms of consuming much shorter grass when food quality is low as well as feeding for more lengthy periods at a time. During dry periods when all that remained was dry unburned dry grass the crude protein levels which are essential for normal functioning were found to be just above maintenance levels. During periods where crude protein levels are low the antelope are severely susceptible to stress and cold snaps and during this time a sever col snap resulted in the death of all the calves and a large proportion of the adult population.

THEN:Applying it to Kruger
From this study, by looking at a healthy population and making use of data collected from the KNP whose sable and similarly roan population (the antelope are extraordinarily similar) are declining and failing to recover
they could start to examine the possible reason for this problem.

Climatic extremes:
Data shows that major droughts occurred in Kruger during 1984/85 and again in 1990/91 although this corresponds fairly well with the initial decline in the population it is most likely not the primary cause as droughts have a delayed effect on population numbers particularly when the animals in poor condition fail to breed. During those time periods Kruger also experienced a decrease in the length off their wet seasons.

competition:
On comparing population data it seems to suggest that the antelope decline when the population of zebra increases. But further analysis shows that although the two seem to correlate that this cannot be the cause as if their is competition for food between animals there will be a decline in calf survival before a decline in adult survival is seen and this was not the case. Also it has been shown that roan and sable utilize a very wide variety of grass species, even tall unpalatable "stemmy" plants. so competition is thus not the cause.

Predation:
The lion population started to increase in 1985 quite dramatically so could predation be the cause?

Management of water points:
By the late 1970's the water points in kruger had increased 5 fold to a point at which the maximum distance to water from any one point was as little as ten kilometres in some places. Historically the north was always much drier than the south so the installation caused water dependent animals such as zebra and wildebeest to migrate northwards and with them they brought about an increase in the lion population This phenomenon where another herbivore appears to compete with another, in this case increasing the lion population is called apparent competition. The water points were later systematically closed and still there has been no recovery, so what is the problem? why can the population not recover. The one big factor is that not only is the northern population decreasing but so is the pretoriuskop population so water points are not solely to blame.

Herd dynamics:
The herd size as well as their distribution (the area they move in) has substantially decreased in both the punda and pretoriuskop populations. They are left with a patchy distribution. Seasonal movement patterns show that sable avoid areas with high concentrations of buffalo and zebra as these animals tend to bring about an increased threat from lion. Distribution also shows that sable appear to inhabit areas with low prey densities and this is clearly visible if the two maps are superimposed.

The remaining groups are generally small and the loss of a few individuals could result in a collapse. The antelope are also insecure against predation and this may contribute to increased stress levels. These factors coupled with poor feeding conditions and the susceptibility of these antelope to these influences when their condition is poor (poor crude protein levels) may account for their decline and inability to recover. So basically it is a suite of interacting characteristics that together cause the problem which makes solving the issue incredibly difficult.

Ok im done, i thought it was quite interesting and I hope i explained it well enough :)

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Thu Jul 15, 2010 8:49 pm 
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Very interesting study Oddesy, thank you so much for sharing!! This sort of thing is right up my alley - facinating read!! :thumbs_up:

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Thu Jul 15, 2010 8:54 pm 
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Thank you Oddesy! Interesting :D On another thread EJ explained recently why the water holes should be limited etc. and what she said fits perfectly with what you have just illustrated :thumbs_up:


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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Thu Jul 15, 2010 9:50 pm 
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Fascinating reading Oddesey, but if I read it correctly then the report is indicating among other things that the water points, or lack of, are not solely to blame for the decline in populations? :?

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Thu Jul 15, 2010 11:22 pm 
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Very interesting reading Oddesy thanks for posting this :thumbs_up:

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 12:19 am 
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Hi Oddesy
As good a read as any I've found on these forums. Some really interesting points and I hope that you enjoyed researching as much as we've enjoyed reading. :D

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 12:31 am 
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Great info coming through, Ods. :clap: :clap: Thanks for this. This is, however, quite sad reading.

It is clear from this that competition (directly or indirectly) and waterholes are not the main causes of the decline, so this is actually contradicting the statement that waterholes were to be blamed and the cause of the decline in numbers?

Is there any short term or long term solution. Or is this ultimately predicting total collapse if there is no intervention by man. And what will such intervention entail, or could entail, if any?

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 12:50 am 
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Elzet wrote:
It is clear from this that competition (directly or indirectly) and waterholes are not the main causes of the decline, so this is actually contradicting the statement that waterholes were to be blamed and the cause of the decline in numbers?


I think that is a too strong deduction you are making there Elzet.

I think rather that what this shows is that there were several factors that has combined to cause this situation, of which the water policy was one. What it also shows is that once a natural balance has been disturbed, it may not be as easy as changing one factor to re establish the previous situation.

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 1:10 am 
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Thanks for posting Ods, very interesting reading. :thumbs_up:

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 6:46 am 
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Oddesey, thank you for this fascinating thread. :thumbs_up: There has been a lot of unhappiness by some people about the shutting down of certain water holes and dams. This illustrates just how vital it is to maintain some balance.

Thank you :clap: :clap: :clap: :clap:

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 7:41 am 
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I think this just illustrates how man's interference was the final straw! Perhaps without the added pressure of competition from the water dependant species, the consquent change in vegetation and habitat, and the increase in predator numbers the sable (and roan) might have had a chance to recover. The whole combination was just too much.

This is probably the sort of thing that ultimately lead to extinction of species across the world. A population is at risk, some added change occurs and they cannot cope. Shelford's law applies (there is a limited range of conditions under which an organism can survive - if this range of conditions is exceeded then survival becomes impossible).

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 10:29 am 
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oddesy wrote:
The antelope are also insecure against predation and this may contribute to increased stress levels. These factors coupled with poor feeding conditions and the susceptibility of these antelope to these influences when their condition is poor (poor crude protein levels) may account for their decline and inability to recover. So basically it is a suite of interacting characteristics that together cause the problem which makes solving the issue incredibly difficult.

Oddesy, thank you very much for this, it is fascinating!! :clap: :clap:
It is rather clear that a few factors play a role here.

oddesy wrote:
By the late 1970's the water points in kruger had increased 5 fold to a point at which the maximum distance to water from any one point was as little as ten kilometres in some places. The water points were later systematically closed and still there has been no recovery, so what is the problem? why can the population not recover. The one big factor is that not only is the northern population decreasing but so is the pretoriuskop population so water points are not solely to blame.

Very interesting! :thumbs_up:


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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 10:39 am 
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Thanks oddesy :thumbs_up: Did the people from Wits visit the reserves in other African countries where Sable and Roan are plentiful, to do comparative studies? Reserves like Hwange in Zimbabwe, have healthy populations of these beautiful animals.

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Last edited by Rooies on Fri Jul 16, 2010 11:12 am, edited 1 time in total.

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 10:59 am 
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Glad other mites found it interesting :thumbs_up:

Elsa wrote:
Fascinating reading Oddesey, but if I read it correctly then the report is indicating among other things that the water points, or lack of, are not solely to blame for the decline in populations? :?


Unfortunately they are not the only cause for the decline in the species just one of the many factors that when combined with a number of others have led to the problem.

Elzet wrote:
It is clear from this that competition (directly or indirectly) and waterholes are not the main causes of the decline, so this is actually contradicting the statement that waterholes were to be blamed and the cause of the decline in numbers?

Is there any short term or long term solution. Or is this ultimately predicting total collapse if there is no intervention by man. And what will such intervention entail, or could entail, if any?


It is very sad :( I dont think that it is a contradiction as such but more along the lines of not being the "only" cause. The water points did contribute to the migration of other herbivores and that hugely influences the community dynamics in the area in terms of interactions. Imberbe explained it nicely in that there are many factors that combined lead to an outcome. No single occurence resulted in thgeir decline but those specific combinations did. One of the main problems with Ecology in its early days and still up to even the middle 90's was that ecologists were often determined to find THE cause for a decline in a species or loss of biodiversity but the complexity, dynamics and the interactions between the individual components of an ecosystem are so difficult to understand that there is almost never an easy solution to the problem which in this case is more difficult than most. So nowadays Ecologists aim to look for interacting factors that could lead to the problem.

Unfortunately I do not know if the population can be sustainable in the long term because all efforts of recovery have not been very succesfull :( .I would imagine that any kind of recovery would have to involve intense breeding programmes to incraese individual numbers within the herd to remove that vulnerability factor in which a herd can collapse from the loss of only a few individuals. We may not have even considered the actual cause for their decline or overlooked it. But I will ask my lecturer and see what she says about it.

ecojunkie wrote:
Perhaps without the added pressure of competition from the water dependant species, the consquent change in vegetation and habitat, and the increase in predator numbers the sable (and roan) might have had a chance to recover. The whole combination was just too much.

They may very well have had a chance to recover but this issue also shows how the organisms within an environment influence another and the dynamics of the whole system. Also balance is extremely important like MM pointed out the problem comes in, in maintaining this balance when we do not understand every interaction.


I find this very interesting so I will try to find out some more info about what possible solutions there could be :thumbs_up:

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 Post subject: Re: The Mystery behind the sable and roan decline in KNP
Unread postPosted: Fri Jul 16, 2010 11:02 am 
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It is sad to know that Sable were common in the early days. Roan were never really common, and it is probable that the Kruger habitat is not really suitable to their needs.

As for breeding programs. They have been tried on both species in KNP, without major success.

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