Scientists have cracked a major problem over the use of hair analysis in an effort to provide valuable information on the lifestyle and migratory behaviour of wild equines.
The international team of researchers focused their attention on wild asses and Przewalski’s horses living in the Gobi Desert of Mongolia.
It has long been known that chemical traces in hair can provide valuable information to scientists on the lifestyle of the animal.
In horses, the analysis of tail hair is especially suited as the length of the hair has the potential to provide information over a long period.
However, determining the exact period of time that corresponds to a segment of hair is not easy because it does not grow at the same rate in all horses.
Researchers at the University of Veterinary Medicine in Vienna have now solved this problem. They developed a method to correctly assign individual hair growth to seasons and thus to a specific time frame. The results were published in the journal Rapid Communications in Mass Spectrometry.
Martina Burnik Šturm and Petra Kaczensky, from the university’s Research Institute of Wildlife Ecology, wanted to investigate the ecology of the Przewalski’s horses and wild asses in the Gobi. They looked for answers in the animals’ hair to find out what they ate, drank, and even how they migrated.
However, the researchers quickly ran into a problem. What does 1 centimetre of hair actually mean in terms of time? Does 1 centimetre refer represent one week, one month or more?
Simply measuring how fast hair grew in a particular species did not solve the problem because hair was known to grow at different rates in each individual animal.
Burnik Šturm therefore developed a method to clearly align hair segments to time.
The habitat of free-ranging equids in Mongolia helped her in this approach. The Gobi Desert is subject to extreme climatic conditions. Temperatures vary greatly at different times of year, and so does the composition of the chemical elements in the hair.
By comparing isotope data from hair analysis with satellite information freely available from NASA’s Earth Observing System Data and Information System, she was able to assign a summer-winter rhythm to each hair. This allowed her to calculate the exact time corresponding to 1 centimetre of hair.
She found that, on average, the tail hair of Mongolian wild asses reached 1 centimetre in 19 days. Przewalski’s tail hair took 17 days and the tail hair of domestic horses only 13 days to grow 1 centimetre.
“We found that tail hair growth varies greatly between species and even between individuals,” Burnik Šturm said.
“To assume that closely related species exhibit similar hair growth rates and to use average growth rates for individuals will most probably lead to incorrect results,” she said.
“Isotope analysis of hair is a common method in the study of animal nutrition and migration. Our method makes it possible for the first time to establish exact time lines for an animal’s ecology and behaviour.
“Previous time lines were estimations and not entirely accurate. Now researchers have a relatively simple method with which to correctly interpret their data.”
Przewalski’s horses, wild asses and free-ranging domestic horses all inhabit the Gobi. All three species share the same habitat in a strictly protected area in the southwest of Mongolia.
Usually, closely related species such as these compete for food, especially so in an area such as this, where the grassland is quite barren.
Armed with their new time-line method, the researchers can now address a key question: What allows the animals to coexist in the region?
The project is still ongoing.
For the isotope analysis, the tail hair is cut into 1 centimetre segments and placed individually in little tin or silver cups before being burnt at 1450 degrees Celsius. Isotopes are then measured in the developing gases using mass spectrometry, a method to sort individual atoms by mass.
Today, isotope analysis is used in many different fields. The method can help to determine the regional origin of animals, food or natural fibres. Isotope analysis is also used to detect cases of doping or environmental contamination.
A protocol to correct for intra- and interspecific variation in tail hair growth to align isotope signatures of segmentally cut tail hair to a common time line.
Martina Burnik Šturm, Budhan Pukazhenthi, Dolores Reed, Oyunsaikhan Ganbaatar, Stane Sušnik, Agnes Haymerle, Christian C. Voigt and Petra Kaczensky.
Published in the journal Rapid Communications in Mass Spectrometry. Rapid Commun. Mass Spectrom. 2015, 29, 1–8 DOI: 10.1002/rcm.7196
The full study can be read here.