Wintering mallard survival is unaffected by brief anthropogenic disturbance on protected areas

Human activities in natural areas can impose both lethal and non-lethal
impacts on animals. Furthermore, anthropogenic disturbance is analogous to
predation risk and can cause animals to adjust their behaviors to avoid
humans. Quantifying if disturbance-induced behavioral shifts affect
individual fitness or population dynamics is needed to guide science-based
conservation and management decisions. We experimentally disturbed
GPS-marked mallards (Anas platyrhynchos) on sanctuaries weekly to evaluate
the effects of brief pulses (1 hr) of non-lethal anthropogenic disturbance
on individual survival. We used Cox proportional hazard models to examine
how single and cumulative disturbance affected survival and tested whether
body mass or hunting season mediated the effects of disturbance. One
hundred and eighty-eight mallards were disturbed ≥1 time resulting in 629
disturbance encounters. Only 3 individuals died immediately following
disturbance, representing <0.5% of encounters. Collectively, we
found no effect of disturbance on daily survival, and our cumulative
disturbance model showed undisturbed mallards had lower survival than
disturbed mallards. Standardized body mass or hunting season did not
mediate the effect of disturbance on survival. Together, we concluded no
effect of our brief experimental disturbance treatments on mallard
survival. Instead, diurnal sanctuary use and individual characteristics,
including age, sex, and standardized body mass, affected survival. Diurnal
sanctuary use was positively related to survival, and for every 20%
increase in diurnal sanctuary use, the risk of mortality decreased by 15%.
Additionally, female mallards were 2.7 times more likely to die compared
to males, and juveniles had 53% greater risk of mortality than adults.
Lastly, for every 100g heavier than average mallards were, we found a 23%
lower risk of mortality during our study. If a primary goal of waterfowl
sanctuary is including non-consumptive recreational use, our results
suggest controlled access (e.g., ~1 hr/week) may have minimal effects on
survival and be consistent with multi-use objectives on public lands with
waterfowl sanctuaries. If additional recreational access to support
multiple public uses is a goal on public lands managed as sanctuaries, we
recommend future work identify disturbance thresholds at which point
survival or other fitness metrics are impacted by disturbance related to
public uses of protected areas.