Clark Bethany L, Vigfúsdóttir Freydís, Wanless Sarah, Hamer Keith C, Bodey Thomas W, Bearhop Stuart, Bennison Ashley, Blackburn Jez, Cox Sam L, d'Entremont Kyle J N, Garthe Stefan, Grémillet David, Jessopp Mark, Lane Jude, Lescroël Amélie, Montevecchi William A, Pascall David J, Provost Pascal, Wakefield Ewan D, Warwick-Evans Victoria, Wischnewski Saskia, Wright Lucy J, Votier Stephen C
BirdLife International, The David Attenborough Building, Pembroke Street, Cambridge CB2 3QZ, UK.
University of Exeter, Penryn TR10 9FE, UK.
R Soc Open Sci. 2024 Sep 4;11(9):240708. doi: 10.1098/rsos.240708. eCollection 2024 Sep.
Density-dependent competition for food influences the foraging behaviour and demography of colonial animals, but how this influence varies across a species' latitudinal range is poorly understood. Here we used satellite tracking from 21 Northern Gannet colonies (39% of colonies worldwide, supporting 73% of the global population) during chick-rearing to test how foraging trip characteristics (distance and duration) covary with colony size (138-60 953 breeding pairs) and latitude across 89% of their latitudinal range (46.81-71.23° N). Tracking data for 1118 individuals showed that foraging trip duration and maximum distance both increased with square-root colony size. Foraging effort also varied between years for the same colony, consistent with a link to environmental variability. Trip duration and maximum distance also decreased with latitude, after controlling for colony size. Our results are consistent with density-dependent reduction in prey availability influencing colony size and reveal reduced competition at the poleward range margin. This provides a mechanism for rapid population growth at northern colonies and, therefore, a poleward shift in response to environmental change. Further work is required to understand when and how colonial animals deplete nearby prey, along with the positive and negative effects of social foraging behaviour.
食物的密度依赖性竞争影响着群居动物的觅食行为和种群统计学，但这种影响在一个物种的纬度范围内如何变化却鲜为人知。在此，我们利用21个北方塘鹅繁殖地（占全球繁殖地的39%，承载全球73%的种群数量）在育雏期间的卫星追踪数据，来测试觅食行程特征（距离和时长）如何随繁殖地规模（138 - 60953对繁殖配偶）以及在其89%的纬度范围内（北纬46.81° - 71.23°）的纬度而共同变化。对1118只个体的追踪数据显示，觅食行程时长和最大距离均随繁殖地规模的平方根增加。同一繁殖地的觅食努力在不同年份也有所不同，这与和环境变异性的关联一致。在控制了繁殖地规模后，行程时长和最大距离也随纬度降低。我们的结果与猎物可利用性的密度依赖性降低影响繁殖地规模这一观点相符，并揭示了在极地范围边缘竞争的减少。这为北方繁殖地的种群快速增长提供了一种机制，因此也为应对环境变化的极地转移提供了一种机制。还需要进一步开展工作来了解群居动物何时以及如何消耗附近的猎物，以及社会觅食行为的正负效应。
