Article

Evidence of the Trade-Off between Starvation and Predation Risks in Ducks

Université de Strasbourg, IPHC, Strasbourg, France.
PLoS ONE (Impact Factor: 3.23). 07/2011; 6(7):e22352. DOI: 10.1371/journal.pone.0022352
Source: PubMed

ABSTRACT

The theory of trade-off between starvation and predation risks predicts a decrease in body mass in order to improve flight performance when facing high predation risk. To date, this trade-off has mainly been validated in passerines, birds that store limited body reserves for short-term use. In the largest avian species in which the trade-off has been investigated (the mallard, Anas platyrhynchos), the slope of the relationship between mass and flight performance was steeper in proportion to lean body mass than in passerines. In order to verify whether the same case can be applied to other birds with large body reserves, we analyzed the response to this trade-off in two other duck species, the common teal (Anas crecca) and the tufted duck (Aythya fuligula). Predation risk was simulated by disturbing birds. Ducks within disturbed groups were compared to non-disturbed control birds. In disturbed groups, both species showed a much greater decrease in food intake and body mass during the period of simulated high risk than those observed in the control group. This loss of body mass allows reaching a more favourable wing loading and increases power for flight, hence enhancing flight performances and reducing predation risk. Moreover, body mass loss and power margin gain in both species were higher than in passerines, as observed in mallards. Our results suggest that the starvation-predation risk trade-off is one of the major life history traits underlying body mass adjustments, and these findings can be generalized to all birds facing predation. Additionally, the response magnitude seems to be influenced by the strategy of body reserve management.

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Available from: Cedric Zimmer, Mar 05, 2014
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    • "Songbirds are believed to trade off their body weight between the countering demands of winter survival and escaping predation (Witter & Cuthill 1993;MacLeod, Clark & Cresswell 2008;Creswell, Clark & Macleod 2009;Zimmer et al. 2011), since layering on adipose tissue reduces their chances of emaciation when food is scarce but likely decreases their acceleration when fleeing a predator (Kullberg, Fransson & Jakobsson 1996; Pennycuick 2008; see also Schultner et al. 2013). Similarly, when harbour porpoises Phocoena phocoena are regularly preyed upon by dolphins, they become much sleeker, carrying substantially less body fat (MacLeod et al. 2007). "
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    • "Hence, our study shows that the reduction of body mass in a natural situation might as much as double the effect reported in captivity. On the other hand, it is similar to the 6–16 % reduction reported for Anatidae species chased by a radio-controlled car in indoor experiments (Zimmer et al. 2011), but these large animals store much more reserves and face a much lower starvation risk than the passerines (Zimmer et al. 2011). It is also within the range of the daily variation in body mass reported for Titmice (7–12 %; Haftorn 1989) and similar to the seasonal winter variation found in Blackbirds (13 %; McLeod et al. 2005). "
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