According to a global study, snakes may be declining across the world. <br/><br/>Researchers examined records for 17 snake populations covering eight species over the last few decades, and found most had declined markedly. <br/><br/>For reasons that are not entirely clear, some populations shrank in number abruptly around 1998. <br/><br/>Species in decline include the asp and the smooth snake from Europe, the Gabon viper and rhinoceros viper of West Africa, and the royal python.<br/><br/>Writing in the journal Biology Letters, the researchers describe the findings as "alarming" but say much more work is needed to understand the causes. <br/><br/>Dr Reading's team at the UK's Centre for Ecology and Hydrology ran the study with institutions in Australia, France, Italy and Nigeria.