# A nose for trouble: ecotoxicological implications for climate change and disease in Saiga antelope (S. t. tatarica)

## TL;DR

Saiga antelope mass die-offs are linked to climate factors and pollutants, which may worsen with climate change.

## Contribution

A new pollutant linkage mechanism is proposed, combining climate variables and environmental pollutants to explain Saiga die-offs.

## Key findings

- Relative humidity, dewpoint temperature, and pollutants like Hg, As, Acetone, and SO2 were linked to Saiga die-offs.
- Precipitation events and temperature spikes during calving season triggered the spread of Pasteurella multocida.
- Environmental pollutants from soils formed smog events that synergistically caused mass mortality.

## Abstract

In recent decades, Saiga antelope (Saiga t. tatarica) mass die-offs have become more common. The mass die-off of 2015 in central Kazakhstan, recorded 140,000 individual deaths across multiple herds. Previously, research has shown atmospheric humidity, the bacterium Pasteurella multocida serotype B, and resultant haemorrhagic septicaemia, were the primary cause. However, other synergistic factors may have impacted this process. Here we use a multivariate compositional data analysis (CoDA) approach to assess what other factors may have been involved. We show a pollutant linkage mechanism where relative humidity and dewpoint temperature combine with environmental pollutants, potentially toxic elements (e.g., Hg, As), complex carbon compounds (e.g., Acetone, Toluene), and inorganic compounds (e.g., CHx, SO2) which affected the Saiga during the calving season (start and peak) and at the onset of the mass die-off. We suggest a mechanism for this process. Upon arrival at their carving grounds, the Saiga experienced a sudden precipitation event, a spike in temperatures, and resultant high humidity occurs. The infectious bacterium P. multocida serotype B then spreads. Further, environmental pollutants contained within steppe soils are released to the air, forming localised smog events, these synergistically combine, and mass die-off occurs.

The online version contains supplementary material available at 10.1007/s10653-024-01874-y.