What are mass mortality events?
Imagine waking up, going for your daily morning walk in a popular park and suddenly seeing the ground covered with bodies. This may sound like a horror film, but this is what actually happened to the saiga antelopes in 2015.
Mass mortality events (MMEs) are sudden demographic catastrophes that can affect all life stages and wipe out up to 90% of a population over a short period of time. They are typically associated with several factors, including infectious diseases and extreme weather conditions, such as heat-waves, heavy precipitation, and droughts. MMEs can not only push species to the brink of extinction but can also have other negative impacts including alterations in the structure of food webs. Unfortunately, both the number of MMEs and the number of animals dying in each incident are on the rise (1).
In May 2015, over 200,000 critically endangered saiga antelopes in Kazakhstan died within just three weeks. The loss represented 88% of the local Betpak-Dala population and 62% of the global saiga population (2). The saiga has been suffering from similar mass mortalities and other, smaller-scale die-offs several times, most recently just last year in Mongolia. The saiga MMEs have not all been caused by a single microbial species however a specific bacterium called Pasteurella multocida has played a critical role in the history of saiga mass mortalities. In the next Lab Note, I will tell you more about this ‘tiny murderer’. Until then, you can watch this beautiful 2-minute National Geographic video about saigas and the MME from 2015:
References
1. Fey, S. B. et al.Recent shifts in the occurrence, cause, and magnitude of animal mass mortality events. Proc. Natl. Acad. Sci.112,1083–1088 (2015).
2. Kock, R. A. et al.Saigas on the brink: Multidisciplinary analysis of the factors influencing mass mortality events. Sci. Adv.4,eaao2314 (2018).
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