Sammanfattning

Studies of foraging behaviour and respiratory physiology in breath-holding divers often assume that each dive cycle (dive plus surface duration) is physiologically and ecologically independent within a series (or "bout ") of sequential dives. We tested this assumption using time depth recorders and GPS data for more than 42,000 dives in 1289 bouts by 39 pairs of male and female European shags (Gulosus aristotelis) provisioning nestlings. We found distinct patterns of temporal autocorrelation over several dives within bouts, but this was driven mainly by consecutive dives of the same type, that is, runs of V-shaped (presumably prey searching) versus U-shaped (presumably active hunting) dives. We found no evidence of cumulative physiological effects (i.e. fatigue and/or lowered body temperature) across dives within a bout. However, within-individual variation in dive behaviour revealed complex interactions. Longer bouts were associated with more V-shaped dives, including more and longer runs of V-shaped dives. Meanwhile, more U-shaped dives and longer runs of U-shaped dives acted as limiting factors to bout lengths, with longer bouts being associated with more U-shaped dives only later in the bout. Interactions between bout length and body mass, and between dive order within the bout and body mass, also suggested various size-specific patterns in the temporal distribution of U-shaped dives. Long bouts and bouts ending in longer runs of V-shaped dives were more likely to indicate the termination of foraging activity. However, neither dive type nor bout length predicted whether individuals subsequently (i) stayed to forage in the same location or (ii) moved to a new location to continue foraging within the same trip from the nest. European shags therefore showed temporal non-independence across successive dive cycles and successive bouts of dives, likely as a result of temporal and spatial variation in prey availabilities rather than cumulative physiological effects that might contravene the assumptions in models of optimal dive behaviour.

Nyckelord

dive behaviour; dive cycles; foraging behaviour; marginal value theorem; physiological constraints; TDR; telemetry; temporal autocorrelation

Publicerad i

Ethology
2023, Volym: 129, nummer: 6, sidor: 254-268

SLU författare

• Carlsen, Astrid

  • Institutionen för akvatiska resurser (SLU Aqua), Sveriges lantbruksuniversitet
    
  • Norges teknisk-naturvitenskapelige universitet (NTNU)
  • Norwegian Institute for Nature Research (NINA)

Globala målen

Skydda, återställa och främja ett hållbart nyttjande av landbaserade ekosystem, hållbart bruka skogar, bekämpa ökenspridning, hejda och vrida tillbaka markförstöringen samt hejda förlusten av biologisk mångfald
Bevara och nyttja haven och de marina resurserna på ett hållbart sätt för en hållbar utveckling


UKÄ forskningsämne

Etologi
Zoologi
Ekologi


Publikationens identifierare

DOI: https://doi.org/10.1111/eth.13362

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/121173