Suomeksi
 
 
The effects of food availability and predation risk on life-history traits and antioxidant physiology
​Pied flycatcher male

​Predation, food and antoxidants

We present the first study in a wild vertebrate, addressing the combined effects of experimental food supplementation and increased predation risk on life-history traits and antioxidant status of female pied flycatchers (Ficedula hypoleuca). Food-supplemented nests received daily protein food supplements (larvae of Tenebrio molitor) during nest building and egg-laying stages. In the predator treatment nest-box entrances were sprayed daily with stoat (Mustela erminea) urine to simulate high predation risk. Nests assigned to “predator + food” were manipulated with both treatments.
 
Our key finding was that experimentally increased food availability increased body mass and decreased antioxidant levels, potentially via lower free radical production allowing downregulation of antioxidant defenses (Read more of the specific antioxidant responses in the paper!). However, higher predation risk per se did not appear to influence antioxidant physiology. Either food supplementation or predation risk did not affect reproductive parameters. Our results thus suggest that for a similar level of reproductive investment, access to higher food availability can potentially decrease ROS and the levels of antioxidant defences, and thus ultimately the cost of reproduction.  Importantly, our full factorial design allowed us to study their combined effects, and the results suggest that the effect of food availability was independent of predation risk.
 
Thus, our results show that food resources may have a stronger impact than predation risk on altering female antioxidant status during breeding. Characterizing the various physiological responses of the prey to altered predation risk, while controlling for the impact of food resources, is important in understanding the big picture of predation risk on prey populations. To fully understand how the cost of reproduction via oxidative stress is affected by environmental conditions, experimental manipulations of reproductive effort, combined with manipulations of the environment, should be conducted.

Suvi Ruuskanen
3.4.2017
 
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