Identifying notches in the ears can be seen on one of the rhinos at Uganda's Ziwa sanctuary.
Uganda has begun microchipping its rhinos as part of a global effort to fight poaching and the illegal trade in rhino horn.
The chips are being implanted in the small rhino herd at the country's breeding sanctuary.
"Many poachers and traders of illegal rhino horn have escaped conviction due to a lack of evidence that the courts would accept as beyond reasonable doubt," said Angie Genade, executive director of Rhino Fund Uganda. "Microchips help in creating the necessary evidence chain in a timely way as you just need to scan the chip to get an immediate result."
The procedure, done by specialists from the Uganda Wildlife Authority, Kenya Wildlife Service and Rhino Fund Uganda, involved anesthetizing each rhino so that microchips could be implanted in both of its horns and under its skin.
Each rhino had a microchip injected into each horn and one under its skin.
"Each rice grain-sized chip carried a unique bar code," Genade explained. "If a rhino was to get poached and the horn recovered thousands of kilometers away, in the Far East for example, the chips could be scanned and matched to those under the skin of the poached carcass to prove it was obtained illegally."
"This indisputable evidence would then be used to convict the smugglers and traders involved," she said.
Rhinos are killed by poachers almost exclusively for their horns, which sell for tens of thousands of dollars.
Experts say that rhino horn is becoming more lucrative than drugs. The demand is driven primarily by buyers in East Asia, who believe it cures various ailments.
In the process of microchipping the relatively small herd in Uganda, DNA samples were collected from each rhino.
"DNA is like a genetic fingerprinting system with every rhino having a unique pattern," said Felix Patton, the conservation adviser to RFU. "DNA is the same for an individual rhino whether it is extracted from its horns, hair, blood or skin and, in fact, we collected samples from all these for each of the rhinos we darted."
The samples will be sent to a laboratory in South Africa for analysis and will become part of an Africa-wide database of rhino DNA.
"Whenever a trader is arrested with rhino horn, the DNA can be extracted and matched to a rhino on the database, similar to the way fingerprints are, to provide further evidence of it being obtained illegally," Patton said.
"Analysis of the DNA of the rhinos will also be used to clarify which of the males is the sire of those rhinos born at Ziwa (Rhino Sanctuary) to ensure that no male is so dominant that there will be genetic problems in the future," he said.
Protecting Uganda's precious rhinos 08:18
The team took the opportunity to put identifying ear-notches on the rhinos which had none and to modify others where the notches were not clearly defined.
Initial identification of a rhino in the field is by visual observation, but since many rhinos look very similar, at least to humans, mistakes can be made. In order to improve the accuracy of identification a system of notches -- small V-shaped cuts at special places on the ear margin -- has become widely used throughout Africa.
"The horns are a major identification feature and, of course, poached rhinos have no horns so are hard to identify if there is not another clear feature to use. Notching creates this feature," Genade explained.