What is the future prospect for the black rhinoceros in Kenya?

Pedersen

 

Throughout the centuries all species of rhinoceroses have been shot as vermin, as hunting trophies and for their meat. They have been cleared from land used for human settlement, and their habitat have been destroyed gradually through land managment practise and human encroachment. The eastern black rhinoceros ( Diceros bicornis michaeli ) is no exception. Its current strong hold is Kenya, but histrorically it was distributed from southern Sudan, Ethiopia and Somalia, through Kenya and into north central parts of Tanzania. In 1997 it was estimated around 424 induviduals as the total black rhino populatinon in Kenya.

 

My reasearch  paper “ Population dynamics and future consevation of a free- ranging black rhinoceros ( Diceros bicornis ) population in Kenya “ is trying to give a picture of the situation for black rhinos in a part of Kenya called the Masai Mara National Reserve (MMNR). This is a large unfenced area of rhino habitat, with free ranging rhinos. The paper is analysing the situation over a 12 year periode, where they use daily monetoring to assess the recovery and performance of  a key Kenyan black rhino population.

 

MMNR is a 1510 km2 protected area in the south west part of Kenya. It’s the most northern part of the world famous Serengeti-Mara ecosystem, and is the key refugee for the black rhino. In the 1960’s it contained  around 150 individuals, with a decrease to 108 induviduals in early 1970’s. Even further poaching and illegal hunting declined the population even more, and by the early 80’s the population held only 15 induviduals.

The MMNR is important for the black rhino for several reasons, one of which is the fact that it holds the only free-ranging population of the sub species Diceros bicornis michaeli in Kenya.

Since the mid 80’s it has been patroled by vehicle twice daily in the MMNR area by a team of Narok County Council ( NCC ) rangers. Over 90 % was done in the Keekorok section. The patrols took place between 0600-1100 in the morning, and 1600-2000 in the evning. From 1992 until 1999 two of the authors of the research paper joined the NCC rangers and used GPS surveveillance to record accurat location of the sigthed animals. Recognition of individual rhinos was made by features like age, sex, horn shape and size, body shape and nose wrinkle patterns.

The estimatin of the population was made for a 2 years periode, starting every January from 1988 to 1998. Every rhino sighted was added to the esstimate of that periode. This metode take in to account “disaperences” of unknown causes, because only sighted rhinos are counted.

Since the registration of animals lasted for such a long continuous period, it was possible to age all anaimals up to 12 years, by reference to theis month of birth. Induviduals was classified into 6 age and sex categoris:

• < 3 or 3 years old ( male or female )
• sub-adult male ( 4-7 years )
• sub-adult female ( 4-5 years )
• adult ( male or female )

Number of parameters ( sex ratio, inter- calving interval ....) was esstimated and compaired with earlier studies in MMNR. The ratio of male:female was in 1998/1999 1:1,2 while in 1971/1972 it was 1,2:1. Around 61% of the population in 1998/1999 was more the 4 years old, while in 1971/1972 the value was 73%. The value of females with calves was also higher in the period 71/72 than 98/99. Also the intercalving interval was slightly longer than average 35 months when calculated in 98/99. There was also a difference in the age composition of the “dissapeared”  induviduals, and the result suggestes that more than expected sub-adults have dissapered from the population.

Density estimations were made for each period by dividing population estimates by the appropriat area of distribution. This was compared to density estimations from earlier studies.

In 1988 20 rhionos were observed in MMNR. When only considering birth, death and immigrations the population grew to 43 induviduals by 1999, with a mean annual growth of 7.2%. However using the 2 year methode, the population reached its peak in 1993/1994 of only 35 induviduals, befor declining to 23 in 1998/1999. This decline is the result of  16 “dissaperences” between 1994 and 1999, comared with only 4 between 1988 and 1994.

This decline in population size was also mirrored in a decline of sightings per patrol and sightings per patrol houre between 1993 and 1999.

 

Time period	Area ( km2 )	Number of rhinos	Density ( rhino/ km2)
1971/1972 ( Total )	749	108	0.144
1971/1972 ( Keekorok)	395	72	0.182
1994/1995	345	31	0.090
1997/1998	370	27	0.073
1998/1999	254	22	0.087

 

We can say that the Mara rhino population mad a partial recovery until the mid 1990’s, after a decline of nearly 80% due to poaching. The recent decline is due to the fact that 20 individuals seen during the period of survaillance no longer could be accounted for. There are three possible explanations for this:

One: they may still be present, but have become either shy or more nocturnal, and thus dissapering from the observations.

Two: they may have died either naturally or unnaturally

Three: they may have left the MMNR, moved into adjacent areas.

Although  nr 1 seems highly unlikeliy, the possebility of animals moving out of the MMNR or that they have died is more likely. When comaring data, the relativly balanced age structure suggests more closely to illegal killing than natural death. Either way, it would be expected to find more carcasses, but then again this could be explained by the fact that the surveillance is done by vehicle, which makes it difficult to get to thicker bushes where carcasses may be hiden.

The relative low population density gives rise to the question why individuals would need to move out of the area. It is belived that the carrying capasity of MMNR may have lowered as a result of declining woodland. The small sized population also raises concerne regarding long term genetic viability.

 

There are many things that can be done with regard to clarifying the situaton. One thing is that it would be valuable to insert foot patrol, rather than only vehicle. It was also recognised the need for coordinated surveillance by trained personel in collaboration with Kenyan counterparts. There is also a question of the genetic viability of such a small population. The paper concludes that it would be advisable to: ensure adequate protection over the whole range, be sure of the effects of small population size on the viability of rhinos, and ascertain the effective poputalion size through wider monitoring.

 

Without doubt, demand for rhino horn has been the primarily factor responsible for the catastrophic decline in rhino number all over Africa, particularly in the second half of the 20^th century. The simple and undeniable fact, is that if there was no demand for rhino horn, there would be little or no poaching. Rhino horns has been one of the most reverded ingredients in pharmacopoeia of traditional Chinese medicine for centuries. It is used for high fever, influenza convulsions, hepatitis, leukaemia, epilepsy and many many more things.  

It is also internal threats like civil war, political instability, poverty, corrution and land tenure threataning the surrvival of the rhinoceros.