Game Warden

Kruger rhino numbers in crisis, says expert

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Reports www.oxpeckers.org

Official numbers of white rhinos in the Kruger stand between 8 000 and 11 000, according to their surveys. However, Dr Kobus du Toit, a rhino expert, wildlife veterinarian and biologist, says these numbers are impossible.
According to Du Toit, there are more than 1 500 but less than 3 000 white rhinos left in the park, and he challenges any ecologist to refute his figures.


To read the full article, click here.

If these figures are correct, then rhino are in seriously peril indeed.

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Posted (edited)

The problem is that extrapolating counts from one block to the whole park is risky, but I assume this technique was used as it is the same ecosystem everywhere and densities should not vary. Can experts tell me more about it?

 

On the other hand, when we want reliable numbers, we opt for the total count method, which is the technique used in Nepal. They do so on elephant back as they need to find the rhinos inside the tall elephant grass. It is also a way to avoid tigers and other predators I guess.

Is a similar technique feasible to implement in the Kruger ecosystem?

Edited by jeremie

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I am confused and have forwarded this to a colleague in the area. The game count conducted some time ago made sense against previous counts and poaching statistics. What we have to remember is that by far the most money is being spent on protection inside Kruger - yet 60% of the poaching is still going on there.

 

If this is true - then it highlights two things 1. Money and militant anti-poaching are not enough on its own, and 2. Private rhino owners may have closer to 50% of the rhino population.

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The problem is that extrapolating counts from block to the whole park is risky, but I guess this technique was used as it is the same ecosystem everywhere and densities should not vary. Can experts tell me more about it?

 

 

That was my initial response also @@jeremie . I know comparatively little about this but if the samples avoided the heavily poached areas it could distort the extrapolated figures produced by SAN Parks Perhaps @@Bugs can find out more...

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My source says that the number is closer to 7000.

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Thanks @@Bugs I really prefer this number. I guess there is around 400 new calves per year in Kruger, thus if more than 400 rhinos are poached per year, the global population decreases...

 

I call for army camps all along the frontier with Mozambique, correctly equipped with nocturnal vision binoculars, patrolling by night, as it is done in Nepal that reached zero poaching.

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The problem is that extrapolating counts from one block to the whole park is risky, but I assume this technique was used as it is the same ecosystem everywhere and densities should not vary. Can experts tell me more about it?

 

On the other hand, when we want reliable numbers, we opt for the total count method, which is the technique used in Nepal. They do so on elephant back as they need to find the rhinos inside the tall elephant grass. It is also a way to avoid tigers and other predators I guess.

Is a similar technique feasible to implement in the Kruger ecosystem?

 

There are actually some pretty convincing arguments that extrapolating counts from one block to other block can't and shouldn't be done at all...

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I'll have to retract my words. They actually can extrapolate the counts from the blocks they count as they randomly select the blocks to count. The clue is in 'randomly'.

 

I read through the piece from Du Toit, and refabricated his numbers. Using growth rates of 7% and 8% I get very similar numbers to his and then it seems impossible that Kruger has the number of rhinos it claims to have. However, the population growth seemed to have increased from the first years after introduction, and if the population growth increased to somewhere between 9-10%, the numbers claimed to be in the park by SANparks are very well possible, even with the reported off-takes. And a growth rate of 9-10% is very well possible. So I think I'll have to side with SANparks in this matter.

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Thanks @@Bugs I really prefer this number. I guess there is around 400 new calves per year in Kruger, thus if more than 400 rhinos are poached per year, the global population decreases...

 

I call for army camps all along the frontier with Mozambique, correctly equipped with nocturnal vision binoculars, patrolling by night, as it is done in Nepal that reached zero poaching.

 

~ @@jeremie

 

I remember the impressive information posted about Nepal's unrelenting effort.

That news was shared here, to bring to the attention of students that conservation requires commitment...and night vision equipment!

Tom K.

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The Peace Parks foundation had just made a donation to Kruger NP rangers, who will now be equipped with night vision equipment to protect the rhinos from poachers during night. This is a great move to fight during night, when poachers are active inside the park.

 

http://africageographic.com/blog/night-vision-equipment-donated-help-combat-poaching/

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I'll have to retract my words. They actually can extrapolate the counts from the blocks they count as they randomly select the blocks to count. The clue is in 'randomly'.

 

I read through the piece from Du Toit, and refabricated his numbers. Using growth rates of 7% and 8% I get very similar numbers to his and then it seems impossible that Kruger has the number of rhinos it claims to have. However, the population growth seemed to have increased from the first years after introduction, and if the population growth increased to somewhere between 9-10%, the numbers claimed to be in the park by SANparks are very well possible, even with the reported off-takes. And a growth rate of 9-10% is very well possible. So I think I'll have to side with SANparks in this matter.

 

I also had a chance to look at the spreadsheet he worked on and agree with the above. He assumes a 1:1 sex ratio and has a founder population of 380 in 1973. In the case of a founder population is it usually heavily biased towards females than to males. The slightest difference here could have an influence on projected numbers in 40 years time.

 

What is interesting is the huge difference in numbers if you add just 1% to the annual population growth over 40 years.

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Just to add to the methodology, the British Trust for Ornithology uses a block system for their bird atlas which informs a lot of scientific work with populations, as @@egilio says the trick is in choosing the blocks to be representative, depending on different terrain types

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Posted (edited)

Just to add to the methodology, the British Trust for Ornithology uses a block system for their bird atlas which informs a lot of scientific work with populations, as @@egilio says the trick is in choosing the blocks to be representative, depending on different terrain types

 

Representative or randomly? I thought @@egilio said the key was to select the block randomly, instead of selecting a representative block.

I agree with you @@Towlersonsafari, that selecting blocks representatively sounds more accurate, but I am not a specialist at all even if I work with probabilities and statistics as an engineer.

Edited by jeremie

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Forgive me @@jeremie for confusing the issue! As I understand it, which probably means its wrong, the squares would be randomly chosed form a representative sample-I suppose people available to look for rhino, difficulties in surveying some types of terrain , etc are problems the Kruger has that are not encountered by someoine doing a survey of a kilometre block in the UK looking for evidence of , say cuckoos!-The BTO website has a "science" section that explains their methodolgy for the surveys they do-and I think it changes for different surveys-I will stop waffling and point you in that direction!

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If you chose 'representative' blocks you very clearly need to describe how you chose them. If you chose them because you know the species is represented there, then you're ignoring blocks where the species is not represented (or so you think). You might count more animals, but you can't extrapolate your count to blocks you didn't count as you assumed the species is not represented there, or less represented. If you do extrapolate your count you're making a fundamental mistake. In my example here you would be overestimating the population, but it can also work the other way around.

If you select the blocks randomly, ie, you don't select them based on anything but chance you will count both high density and low density blocks, and even blocks with no counts, giving you a better (more representative) total number/density.

You could argue to chose representative blocks in each of categories (you define, ie high density, medium density, low density) but if you already know that, than why bother? And what if you were wrong in hindsight? You could stratify your design based on other characteristics (ie based on habitat) where in each category you randomly select a certain number of blocks to count (ie 5 in mopane, 5 in scrub, 5 grassland etc) or even based on the size of each class (3 out of 30 blocks in mopane, 5 out of 50 blocks in grassland etc).

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OK! The keys is then selecting randomly many blocks. If selecting the blocks representatively, it will under/estimate the population. If selecting few blocks, there might be significant bias.

Thank you very much for this detailed and complete explication.

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Yes, if the area is divided in 100 blocks then only surveying 1 is obviously wouldn't give you an accurate estimate. Surveying 99 blocks isn't very productive either. The number of blocks to survey depends on the total number of animals (if the animal is really rare and occurs in clusters, like wild dogs, then surveying more blocks would be wise) or, if the animal is spread out pretty continuously and at a decent density (like rhinos in some areas, elephants in some areas), you can get away with fewer blocks. Added to the whole thing is a detectability issue as well, elephants and rhinos are easier to detect than, for example, aardwolfs. Partly you can approach this with different survey methods (obviously you don't do aerial surveys for leopards or aardwolfs) and partly you'll have to estimate your detection rate for the method you use by intensively surveying a few small areas.

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Great!

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Posted (edited)

NO 1 this is very concerning and sanparks lack of regular reporting changing from monthly to almost never does not make anyone confident

 

I would treat the oxpeckers report seriously

 

NO 2

 

If anyone has serious specific information , or a source who is willing to speak on a confidential basis , there are 2 major NGO'S interested a group of forensic investigations who work with the Born Free foundation can be contacted at wildlife@c4ads.org and the Environmental Investigation Agency their president responded to my leads info@eia-global.org

Edited by COSMIC RHINO

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