Rhino Numbers and Census

[Richprins]

I think the biggest underlying factor is that there is no accurate census of rhino numbers in Kruger!

[Lisbeth]

Yes, it is useless to discuss if we cannot trust the figures

[graham]

Then we should not be discussing articles such as “Shocking statistics reveal that Kruger rhino population has dropped by nearly 70% in 10 years” and “Kruger rhino populations plummet – latest official stats” because they too are based on figures we can’t trust.

Modelling provides an opportunity to combine the limited information available and to examine what is plausible and what is not.

But it seems to me this is often a case of not wanting to give any degree of credence to any of Sanparks figures, be they counts, removals or poaching cases (and remember that higher removals and higher poaching implies higher earlier populations) because it doesn’t suit the agenda. Sanparks management failings should not automatically be attributed to the underlying science.

So yes, I agree there is nothing further to be said.

[Klipspringer]

This paper shows how the population is affected not only by poaching, the natural mortalities and birth rates change due to drought


https://journals.plos.org/plosone/artic ... 09678-t002

[Richprins]

Valid points, graham.

Maybe agendas on both sides. Either way, SP must be kept on its toes, and as you say we cannot die wondering should rhinos have disappeared one day.

[Sprocky]

[Lisbeth]

[Richprins]

Counting Kruger’s rhinos

15 March 2021


Dr Sam Ferreira
Specialist Scientist: Large Mammals


Dr Danny Govender
GM: Savanna and Grassland Research Unit


Dr Stefanie Freitag-Ronaldson
GM: Garden Route and Frontier Research Unit


Dr Luthando Dziba
ME: Conservation Services



Photo by Cathy Greaver, Savanna and Grassland Research Unit, SANParks

Numbers of animals are often of interest and importance for conservationists and the public. Trends in numbers are key indicators of conservation effectiveness. There are numerous ways to determine how many individuals of a species live in a park at a specific time, including aerial surveys, call-up surveys, dung counts and camera trapping. In smaller areas, individual identification allows registration studies like wild dog and cheetah photo censuses. These require an identity register of every animal (similar to ID registration of citizens at Home Affairs), which can be difficult for certain species that are not easy to photograph. In some instances, mark-recapture methods use the re-sighting probability of marked individuals to determine what proportion of the population observers missed and thereby helps derive total population size. Another approach is a total count, which is like a human population census – observers work through the entire park and count every individual they see. Applying total counting methods in large areas is easier if surveyors use a helicopter, fixed-wing aircraft, or even drones.

Aerial approaches for counting animals should be easy, right? To check if this is true, take 30 seconds to count the number of elephants you see in the aerial picture below



Photo by Conservation Ecology Research Unit, University of Pretoria

Now compare your count to the number of red dots on the same picture below – there are 10 to be precise! Your count was most likely less than 10 as the number of elephants are hard to see because they are under trees. Your count suffered from one type of bias, namely availability bias!



Photo by Conservation Ecology Research Unit, University of Pretoria

There is also a good chance that someone else counts a different number of elephants on the picture than you do. You most likely have different observation skills – which leads to observer bias. You have just experienced two of the factors that influence surveyors every year when they count rhinos!

Both total counts and surveys that count animals on a sample of blocks suffer from these kinds of problems. They include detectability, availability and observer biases that affect the accuracy of a count as well as sampling and survey errors that influence the precision of any estimate of population size. All of these affect our ability to detect changes (see infographic).



Infographic by Corli Wigley-Coetsee, Savanna and Grassland Research Unit, SANParks

Given all these biases and sample errors, which affect the accuracy and precision of our estimates, we use statistical confidence intervals – that is the estimated range with a 95% chance of including the actual number of rhinos. We report our actual estimate within the 95% confidence interval as well as the range around this when we report rhino population sizes. The narrower the confidence interval, the better the precision of the estimate.

What works best for rhinos? This depends on the size of the area as well as the size of the rhino population. Generally, larger areas with more rhinos lend themselves to the use of aerial count techniques. However, dense vegetation affects the use of aerial surveys, as these are not good for elusive animals living in dense forests, such as the Javan rhino.

In Kruger, we estimate the population size for white and black rhino through a sample block counting method. We survey 50% of the total area (Kruger is almost 2 million hectares) using 3 km x 3 km blocks randomly placed across 35 different landscapes and then extrapolate for the whole park.

So, why don’t we just survey the total area? Research, including our own study, shows that the precision of a population estimate improves as an aerial survey covers more and more area until the coverage gets to about 40% of the total area. At this point, the precision of a population estimate levels off so that more counting does not give a better population estimate. We, therefore, settled on counting 50% of the total area to get meaningful and efficient estimates of rhino numbers in terms of time and money. Bear in mind that a typical rhino survey in Kruger takes a month and costs almost R 2 million in aircraft costs alone.

So how do we get from the total number counted on the blocks to a population estimate for the park? We use a well-known estimation process that calculates the density of rhinos on the blocks surveyed within a landscape type. By multiplying that density by the total area of that landscape type in Kruger; correcting for availability, observer and detectability biases; and using the range of density estimates on blocks within the same landscape, the method provides an estimate and the 95% confidence interval for the number of rhinos in that specific landscape. Adding the total numbers estimated for each of the 35 landscapes then gives the rhino estimate for Kruger.

These influences of biases and sample error are very prevalent even when authorities do total counts. You may hear a single, clean figure being presented with total count estimates, but as you have experienced with counting elephants, this cannot be the case, especially when counting animals over very large areas.

Thus, counting rhinos (or other large animals across large landscapes) using aerial observations is not as easy or predictable as counting the money in your wallet. Scientists take into account the many influences affecting population estimates to explain the study caveats and must present the uncertainty in the data. This is not a result of poor study design, but in recognition of the limitations of methods used and the inherent variability in the biological systems we attempt to measure. Nevertheless, repeated population estimates, taking into account the various biases and errors, show trends over time. These are important for understanding how populations respond to threats and management actions designed to address those threats.

https://www.sanparks.org/scientific-ser ... ers-rhinos

[Lisbeth]

Nothing new there. It is all very obvious. If it was done more often it would be easier to get an idea of the numbers, but looking at the cost, this is to ask too much I suppose.

[Lisbeth]

White rhino population down by two-thirds, new global report says

BY SIPOKAZI FOKAZI - 21ST SEPTEMBER 2021 - HERALD

The estimated rhino population in Africa is about 18,000, which represents a 12% decline in the past decade, according to the latest State of Rhino report, published by the International Rhino Foundation .

Poaching continues to put rhino populations in Africa under threat, and in SA alone the white rhino population — once thought to be the largest population in the world – has plummeted by more than two-thirds within eight years, a new report suggests.

According the latest State of Rhino report, published by the International Rhino Foundation every September ahead of World Rhino Day on September 22, the estimated rhino population in Africa is about 18,000, which represents a 12% decline in the past decade.

After experiencing a decline in poaching in 2020 due to closure of borders as a result of the Covid-19 pandemic, white rhino poaching incidents in SA are again on the rise, the report states. In the first half of 2021, SA experienced higher poaching numbers than last year, but fewer deaths compared to the same period in 2019.

Apart from a jump in poaching in the Kruger National Park, authorities have also noted a rise in poaching figures in other areas of the country, possibly due to fewer rhinos in the park.

SA National Parks (SANParks) released a report indicating that the total white rhino population in Kruger National Park – once thought to be the largest population of white rhinos in the world – had plummeted 67% from about 10,621 in 2011 to just 3,549 individuals in 2019.

After experiencing a decline in poaching in 2020, due largely to border closures and the Covid-19 restrictions, the report says white rhino poaching incidents are again on the rise.

The report noted that even though Africa’s black rhino remains an endangered species, it has seen an encouraging population increase of about 17% over the past decade – to more than 5,600.

Namibia hosts the largest population of black rhinos in Africa and its Etosha National Park has the world’s largest black rhino population. Rhino numbers are increasing steadily, thanks to the government’s innovative conservation efforts.

On the other hand, Kenya is celebrating the first zero-poaching year in 21 years. Kenya’s worst year for poaching was in 2013 when 59 animals were killed, more than 5% of the national population. The poaching rate has since declined, with just four animals poached in 2019 and none during 2020.

Authors of the report say even though rhinos are found in nine African countries – SA, Botswana, Eswatini, Kenya, Malawi, Namibia, Tanzania, Zambia and Zimbabwe — not all countries report rhino populations or poaching data.

“Demand for rhino horn destined for black markets remains a top threat to the survival of rhinos,” said Nina Fascione, executive director of International Rhino Foundation.

“Continued co-ordination between countries for law enforcement is vital to breaking the hold of international criminal syndicates on trade.”

In an effort to restore endangered rhino populations, conservation experts are now turning to assisted reproductive technology, which continues to show promise.

In July of this year, scientists working to bring back the functionally extinct northern white rhino announced they had successfully created three additional embryos of the subspecies, bringing the total to 12. They used eggs collected from Fatu, one of the last two remaining northern white rhinos in Ol Pejeta Wildlife Conservancy in Kenya, and sperm from two deceased males.

A scientific consortium, Biorescue, is leading the research with co-operation from the Kenyan government. “The eggs are being fertilised in a lab in Italy. Due to their advanced age, neither of the remaining northern white rhinos are capable of carrying a calf to term, so a surrogate mother will be selected from a population of southern white rhinos if a viable embryo is developed,” the report noted.

“Labs across the world are conducting additional artificial reproductive technology (ART) research in an effort to better understand its application to rhino conservation. The foundation continues to monitor achievements in ART with great interest. Any gains in the understanding of the science behind rhino breeding could prove extremely useful.”

Wildlife crime is an ever-evolving challenge and requires collaboration and co-ordination within and between countries, as rhino horn trade is controlled by large criminal syndicates that operate multinationally.

While the act of poaching is often the most visible and most readily understood part of wildlife crime, the report noted that “it is the transport, trade and sale of illegal rhino horn from the protected area, across provincial boundaries and national borders and all the way to the end consumer that makes this type of crime not just possible, but also profitable”.

“During the past year, there have been some large seizures of rhino horn and several high-profile arrests of suspected wildlife trade criminals by authorities in SA, India and Vietnam. Training is ongoing to better analyse and secure crime scenes, collect evidence and provide testimony to convict wildlife criminals. In Vietnam, authorities have worked to secure longer sentences for wildlife criminals as a deterrent,” the authors said.

Original article: https://www.heraldlive.co.za/amp/news/2 ... ssion=true