  The accidental oil spill in the Gulf of Mexico in 2010 has caused perceptible
damage to marine and freshwater ecosystems. The large quantity of oil leaking
at a constant rate and the long duration of the event caused an exponentially
increasing mortality of vertebrates. Using data provided by NOAA and USFWS, we
assessed the effects of this event on birds, sea turtles, and mammals.
Mortality rates (measured as the number of carcasses recorded per day) were
exponential for all three groups. Birds were the most affected group, as
indicated by the steepest increase of mortality rates over time. For sea
turtles and mammals, an exponential increase in mortality was observed after an
initial delay. These exponential behaviors are consistent with a unified
scenario for the mortality rate for tetrapod vertebrates. However, at least for
mammals, pre-spill data seem to indicate that the growth in the mortality rate
is not entirely a consequence of the spill.
