Résumé
Wildlife is increasingly exposed to sublethal transient cancer risk
factors, including mutagenic substances, which activate their anti-cancer
defences, promote tumourigenesis, and may negatively impact populations.
Little is known about how exposure to cancer risk factors impacts the
behaviour of wildlife. Here, we investigated the effects of a sublethal,
short-term exposure to a carcinogen at environmentally relevant
concentrations on the activity patterns of wild Girardia tigrina planaria
during a two-phase experiment, consisting of a 7-day exposure to cadmium
period followed by a 7-day recovery period. To comprehensively explore the
effects of the exposure on activity patterns, we employed the double
hierarchical generalized linear model framework which explicitly models
residual intraindividual variability in addition to the mean and variance
of the population. We found that exposed planaria were less active
compared to unexposed individuals and were able to recover to pre-exposure
activity levels albeit with a reduced variance in activity at the start of
the recovery phase. Planaria showing high activity levels were less
predictable with larger daily activity variations and higher residual
variance. Thus, the shift in behavioural variability induced by an
exposure to a cancer risk factor can be quantified using advanced tools
from the field of behavioural ecology. This is required to understand how
tumourous processes affect the ecology of species.