Mass animal die-offs on the rise

University San Diego Assistant Biology Professor Adam Siepielski co-lead a study documenting recent changes in animal mass mortality events, including certain species of sea stars, which he is holding at USD in San Diego on Tuesday.

Mass animal die-offs have become more common, and often more severe, in recent years, according to researchers from the University of San Diego, Yale University and UC Berkeley.

Their study, published this week in the Proceedings of the National Academy of Sciences, analyzed 727 scientific reports of mass mortalities that affected 2,407 animal populations. The die-offs increased by about one event per year during the 70 years between 1940 and 2010, and the scale of deaths escalated for some creatures, the researchers said.

The new analysis helps explain what happens when millions of animals perish in a single blow, and sheds more light on the rapid changes in biodiversity that scientists have previously reported.

This sort of analysis will help clarify the relation between mass mortality events and global extinction events, said study co-author Samuel Fey, a postdoctoral research fellow in ecology and evolutionary biology at Yale.

The examination began when co-author Adam Siepielski, an assistant professor of biology at the University of San Diego, watched populations of certain animals vanish from California ponds amid the states ongoing drought.

Over the past few years, many of those have died off over a matter of weeks, said Siepielski, who specializes in aquatic ecology and evolutionary biology. Literally youre not seeing only one species die, but youre seeing entire food webs disappear from lakes or ponds.

The loss of millions of starfish off the West Coast has grabbed headlines recently, as has honeybee colony collapse disorder, in which the pollinators have abandoned their hives en masse.

But the phenomena has many precedents, from the loss of a billion Mid-Atlantic tilefish in 1882 to the viral epidemic that killed 90,000 Baikal seals the only freshwater seal on the planet more than a century later in Siberia.

We believe this study shows that there are some surprising patterns and some shocking trends in the causes and magnitude of mortality events, Fey said.

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Mass animal die-offs on the rise