Zoo and Museum Center Unlocking Secrets Found in Rhino DNA

Posted July 21, 2022

Scientists perform 23andMe-like tests to identify rhino sex, species, and more

Scientists from Cincinnati Zoo & Botanical Garden’s Lindner Center for Conservation & Research of Endangered Wildlife (CREW) are working to develop a method for detecting a potentially fatal rhino condition called iron overload disorder. One of the challenges they’ve faced is that internal iron levels are difficult to monitor but, with help from the Cincinnati Museum Center (CMC), they are testing a novel approach determining if rhino horns hold the data they need. 

“We know that humans exposed to high levels of minerals will have high levels of the same minerals in their fingernails, toenails, and hair, which are all made of keratin,” said Dr. Terri Roth, Director of CREW and Director of the American Institute of Rhinoceros Science (AIRS). “Since Rhino horns are also made of keratin, we think there is a good chance that they will serve as an indicator of body iron levels.  The only other reliable way to determine body iron load is to biopsy the animal’s liver, which is simply not an option in a living rhino.”  

The first step in the process was to test various locations throughout the horn to determine if the sample location might skew results.  After figuring out how and where to sample the horn, the team needed a large number of horn samples from both black and white rhinos to test the hypothesis that iron levels in horns will correlate to overall body iron levels. CREW scientists were able to obtain a good sample size for the study, but in many cases, little was known about the rhinos from which the horns originated.   

“We needed to do some extra CSI work to figure out the species and sex of the individuals that grew those horns.  We also need to know if two horns we sampled came from the same rhino,” said Roth.  “We know that black rhinos suffer from iron overload and white rhinos do not. If this method is going to work at all, we should see a significant difference in the iron levels in black rhino horns compared to white rhino horns” 

CREW scientists prep the horn DNA for analysis in the labs at the Zoo and then use the advanced equipment in the Museum Center’s John A. and Judy Ruthven DNA Lab to perform multiple tests simultaneously.   

  “Using 23 different DNA locations known to differ between rhinos, we create a “’barcode’ for each horn sample. By comparing barcodes, we can determine which horns came from the same individual,” said Louisa Rispoli, Post-Doctoral Scientist at CREW. “By partnering with CMC, we can analyze 20 samples in less than a day, which would otherwise take us several weeks do.” 

Preliminary tests to date have detected iron in the horn samples, so the method certainly shows promise, but it will be some time before conclusive results are in hand.  This study is part of the American Institute of Rhinoceros Science’s  collaborative effort to use science to improve the lives of rhinos in North American Zoos and is supported by a federal National Leadership grant from the Institute of Museum and Library Services.