For our September 9 Zoom meeting, Jane Wiltshire of, speaking remotely from South Africa, gave us her insight into the impact of ongoing killing of rhinoceros for their horns for the illegal international rhino horn trade.  Dr. Wiltshire, in love with rhinos since the age of five, did her Doctoral research on the international trade in rhino horn and the potential for reducing that trade.    View Jane's presentation recording at
White rhinos are a keystone species.  They alter their habitat more than elephants.  Their use of mud wallows both increases the size of the wallows, leading to more permanent water sources for other species, and spreads rich wallow mud over the surrounding area.  They are basically four-legged lawn mowers, maintaining short grass lawns which are good habitats for birds and other species and havens for slow-moving species from fires.  They are very territorial and so don’t move around much.  Black rhinos, on the other hand, live on thorny acacia trees, have much nastier dispositions, and move around much more.
By the way, we learned that the names 'Black' and 'White' Rhinos has nothing to do with color, but instead comes from misunderstanding of words for their characteristics.   
Rhinos, both black and white, weighing in at 1.5 to 2.5 tons, are one of the big five for hunting with either rifle or camera.  In the early 1900's, there were over 1 million black rhinos scattered over most of sub-Saharan Africa; now there are around 5000 in small areas in Southern Africa.  The same sort of population trend has applied to white rhinos, thought to be extinct until some 50 were discovered in the early 1900's.  They were protected and nurtured to a population of over 20 000.  But more recently there has been a significant decrease in their numbers.  These population trends are partly the result of creation of modern weapons, and partly the effort to convert wild “veldt” into marginal stock farms.  Development of techniques for darting and transporting white rhinos and then protecting them in game reserves and in private hands led to a resurgence to a population of some 20,000 as recently as 2015, but there has been a decrease since then.  Elderly males, past breeding age, have regularly been sold on for trophy hunts, thereby allowing younger males to make a more effective breeding contribution. 
There have been a number of efforts over recent years to reduce the amount of poaching.  These include banning international trade in rhino horn.  But under the ban African rhinos became  extinct in 24 out of 29 their former range lands. Increased anti-poaching efforts, trimming of rhinos’ horns to make them a less attractive target, and establishment of behavior-modification campaigns in consuming nations were also tried.  But these efforts have been, at best, only minimally successful, reducing but not eliminating the poaching.  The rhino population in Kruger National Park has recently been reduced by ½ by poaching.  Although de-horning has helped to reduce poaching, with the ban on sale, the trimmed rhino horn (currently some 50 tons of it in is now in vaults in South Africa) cannot be converted to funds.  These or any other efforts at sale might just ignite the market.  There has been some effect of demand reduction in Taiwan and Japan, but no effect in China or the countries of Indo-China.  Although there are numerous organizations around the world that contribute to efforts to reduce poaching, there is only so much money and there is some evidence of “donor fatigue”.
Has there been any genetic or evolutionary impact of the dramatic decrease in population in the mid-1900s?  There is no apparent impact and there are extensive efforts by private breeders to manage herds and breeding to reduce the possibility of impact.  Although the males maintain their territories, the females choose which males to breed with, so there has been considerable success with changing out the males or introducing more males into an area.