What killed the saiga antelopes?


In 2015, in Kazakhstan, nearly 200,000 saiga antelopes died in less than a month. A multidisciplinary and international team of researchers investigated this mysterious hecatomb.

The saiga antelope (Saiga tatarica) is an emblematic species. And not only because of its funny snout! It’s also the only species of Eurasien antelope. A victim of poaching and a shrinking habitat, it’s on the endangered species list. As such, it has been monitored for several years by biodiversity experts.

A ‘lightning’ epidemic

In 2015, a team of scientists was observing the calving season in Kazakhstan when saiga antelopes began to get sick. ‘A few days passed between the appearance of the first symptoms and death’, says Dr Julien Radoux, a bioengineer at UCL’s Earth and Life Institute. ‘In the affected packs, not a single antelope survived. It went very fast. In just three weeks, about 200,000 animals, or 62% of the total population, died.’

What was to blame?

Right away, scientists wondered what could have caused this ‘mass mortality event’ (MME). On-site veterinarians took samples from cadavers and had them analysed in the laboratory. After excluding other viruses and bacteria, the culprit was discovered: Pasteurella multocida type B. This pathogenic bacterium infected the antelopes, causing fatal septicaemia in 100% of cases. ‘P. multocida is latently present in many healthy individuals’, Dr Radoux explains. "It would have caused MMEs in the past, but never of this magnitude. Other factors must have occurred.’ It remained to be seen which ones.

Searching for aggravating factors

Several hypotheses were considered and verified. Were the antelopes in poor health? Did they run out of food? Did they suffer from deficiencies? After analysing samples, the researchers concluded that there was nothing abnormal in the antelopes. The cause had to have been in the environment. At UCL, Dr Radoux works on Lifewatch. This programme collects satellite data on factors (snow, vegetation, fire, etc.) that influence biodiversity in Europe and provides it to other research teams. ‘In 2015, we noticed an anomaly in Kazakhstan: the vegetation was less dense than usual. In addition, temperatures and precipitation were unusually high before and during the MME.’ These are ideal conditions for the development and proliferation of bacteria such as P. multocida! The saiga antelopes paid the price. ‘This hypothesis was confirmed by the two previous MMEs that struck the species in 1981 and 1988’, Dr Radoux adds. ‘It also rained a lot and was very hot in those years...2015 was a record year: the temperature and precipitation differences hadn’t been so great since 1948’.1 In other words, the hotter and wetter it is, the more likely saiga antelopes are to be victims of a bacterial MME.

Multidisciplinary collaboration

These conclusions were published in the American journal Science Advances.2 The study’s distinctive feature is its multidisciplinary and international dimension. Veterinarians, biologists, ecologists, statisticians and bioengineers contributed. Through Lifewatch, UCL provided vegetation and snow data and analysed information that ultimately established the link between P. multocida virulence and environmental conditions. ‘It’s because we collect long-term data that we’re able to identify trends, averages and anomalies’, Dr Radoux says. ‘This is the first time participated in a multidisciplinary study of this magnitude, but it’s probably not the last. After all, our data is valuable information for anyone interested in biodiversity.’

Candice Leblanc

(1) 1948 was when meteorological records began for this region
(2) Richard A. Kock et al., ‘Saigas on the brink: Multidisciplinary analysis of the factors influencing mass mortality events » in Science Advances, January 2018. http://advances.sciencemag.org/content/4/1/eaao2314

A glance at Julien Radoux's bio

2002                 Master’s Degree, Environmental Engineering, UCL
2002-10            Geomatics Assistant, Faculty of Biological, Agricultural and Environmental Engineering, UCL 
2004-06            Stereo-Forecast Project
2006-10            ORFEO-ASSIMIV Project
2010                  PhD, Environmental Engineering, UCL 
2010-11             Projet État du Territoire wallon
2011-12             UNESCO-Watch Project 
2012+2015-16   Land Cover CCI Project
Since 2012         Project Lifewatch 

Lifewatch is funded by the Fédération Wallonie-Bruxelles, ion the framework of the European Research Infrastructure Consortium (ERIC). 

Published on March 22, 2018