Data from: Biologging in a free-ranging mammal reveals apparent energetic trade-offs among physiological and behavioral components of the acute phase response

The acute phase response (APR) is an adaptive emergency life-history
stage, wherein vertebrates exhibit fever and anorexia to survive an
infection. However, induced immune responses are energetically costly and
sick animals may reduce physical activity to compensate. Tests of this
predicted energetic trade-off in free-ranging animals are rare due to
difficulties in measuring individual physiology and behavior under immune
challenge in natural settings. However, recent advances in biologging
technology now make such studies possible. We surgically implanted heart
rate/temperature loggers in free-ranging adult male Arctic ground
squirrels, fitted the squirrels with collar-mounted accelerometers and
light/temperature loggers, and injected animals with lipopolysaccharide
(LPS) to simulate an immune challenge. LPS-injected squirrels exhibited ~1
°C overnight fevers accompanied by slightly elevated (~10 bpm) heart
rates; LPS-injected squirrels also spent ~20% less of their time
aboveground the following day and reduced overall movement by ~40%
compared to saline-injected controls. Thus, we found support for an
energetic trade-off between functional immune responses (fever and
anorexia) and lethargic sickness behavior within the APR of a free-ranging
mammal. Moreover, our results suggest animal-borne devices can play an
important role in future studies of vertebrate immunity and disease
dynamics.