Data From: Effects of disease on foraging behaviour and success in an individual free-ranging northern elephant seal

Evaluating consequences of stressors on vital rates in marine mammals is
of considerable interest to scientific and regulatory bodies. Many of
these species face numerous anthropogenic and environmental disturbances.
Despite its importance as a critical form of mortality, little is known
about disease progression in air-breathing marine megafauna at sea.
 We examined the movement, diving, foraging behaviour, and
physiological state of an adult female northern elephant seal (Mirounga
angustirostris) who suffered from an infection while at sea. Comparing her
to healthy individuals, we identified abnormal behavioural patterns from
high-resolution biologging instruments that are likely indicators of
diseased and deteriorating condition. We observed continuous extended
(3–30 min) surface intervals coinciding with almost no foraging attempts
(jaw motion) during two weeks of acute illness early in her post-breeding
foraging trip. Elephant seals typically spend ~2 min at the surface. There
were less frequent but highly extended (30–200 min) surface periods across
the remainder of the trip. Dive duration declined throughout the trip
rather than increasing. This seal returned in the poorest body condition
recorded for an adult female elephant seal (18.3% adipose tissue;
post-breeding trip average is 30.4%). She was immunocompromised at the end
of her foraging trip and has not been seen since that moulting season. The
timing and severity of the illness, which began during the end of the
energy-intensive lactation fast, forced this animal over a tipping point
from which she could not recover. Additional physiological constraints to
foraging, including thermoregulation and oxygen consumption, likely
exacerbated her already poor condition. These findings improve our
understanding of illness in free-ranging air-breathing marine megafauna,
demonstrate the vulnerability of individuals at critical points in their
life-history, highlight the importance of considering individual health
when interpreting biologging data, and could help differentiate between
malnutrition and other causes of at-sea mortality from transmitted data.